Data-Driven Fasting: How to Lose Weight and Reverse Type 2 Diabetes Without Tracking Your Food (The COMPLETE Guide)

Intermittent fasting has helped many people lose weight, lower their blood sugars, and reverse type 2 diabetes without the hassle of tracking their food.  But, sadly, for many more, fasting doesn’t provide the results they hoped for.  

When we get ravenously hungry, most of us gravitate to energy-dense nutrient-poor foods that quickly undo all our discipline, hard work and restriction.  

To achieve long-term success, you need to find the minimum effective dose of fasting that gives you the results you want without pushing your body so hard that it rebels and leaves you trapped in an endless restrict-binge cycle.  

As with most things in life, more is usually not better.  You just need enough to move towards your goal at a sustainable pace.  

The good news is, you can gamify your weight loss with a few simple measurements.  By quantifying the things that matter, you can optimise your eating schedule to “bio-hack” the outcome you want.  

Data-Driven Fasting is a powerful tool to ensure you lose fat and optimise your blood sugars without having to track calories!  

Download the Data-Driven Fasting Free Manual Now

There is a LOT of information in this article about all the things that set Data-Driven Fasting apart from other popular fasting approaches you may have heard of or tried.  

If you want to download our complete 126-page free guide to Data-Driven Fasting for free to print, mark up and read at your leisure, you can download it here.  

To learn ALL about Data-Driven Fasting, read on! 

Is counting calories the best way to lose weight?

Many people try calorie counting apps like MyFitnessPal.  But the vast majority find it’s unsustainable.  

  • Counting calories may be great if you’re a single bodybuilder who can pre-prepare everything.  But most of us live unpredictable lives with family dinners, work lunches and impromptu parties that make it impractical to weigh and measure everything we eat all the time.  
  • While we can be disciplined most of the time, it’s those occasional meals (when your calorie tracking app isn’t looking) that undo all your hard work.  
  • Even if you were able to weigh and measure EVERYTHING you ate, the data in your app rarely matches the foods you are eating.  
  • Your body doesn’t ‘burn’ the food the same way that calories are measured in a bomb calorimeter (shown below).  
  • Your calorie tracking app doesn’t account for the thermic effect of food that changes depending on the macronutrient profile of your food and the degree of processing.
  • Any calorie target from an online calculator is going to be inaccurate.  Your metabolism is complex, and the amount of calories you require depends on a range of factors, including your muscle mass, exercise, stress and sleep (not to mention pandemics and lockdowns, which restrict your movement).
  • Your energy expenditure changes from day to day.  If you try to maintain a fixed calorie intake, there is a serious risk that your healthy appetite signals will become dysregulated as you try to push through hunger some days and overeat on others.   
  • When you suddenly slash your energy intake, your body quickly adapts to survive.  Your metabolic rate slows.  You produce less heat.  You feel less energetic, and your involuntary activity will reduce.  You “burn” fewer calories day-to-day than you used to.   

Eating is impulsive and instinctual.  Your appetite ensures you seek out the nutrients you need.  However, it also means that, despite our best efforts to limit the amount we eat, our appetite usually wins out in the end, especially if we continue to eat the same food that led us to be overfat in the first place.  

So, while energy is always conserved, the factors on either side of the calories in vs calories out equation are incredibly complex and beyond our ability to manage accurately (even with the latest fitness trackers and apps).  

Counting calories can cause you to develop an eating disorder

If you’ve ever tried tracking your calories, you will understand that your lizard brain doesn’t like to relinquish control of your appetite to a smartphone app.  

While calories in vs calories out sounds seductively simple, your reptilian instincts fight for control when awoken by the threat of starvation!  It’s critical to keep your inner lizard fed with high-quality food, so it doesn’t sense an emergency and stays asleep.  

Many people become anxious when they put so much effort into tracking everything they eat and don’t get the results they hoped for.   Sadly, food tracking can drive an unhealthy neurosis in many people.   

A 2017 study of people with a diagnosed eating disorder found that 75% of participants reported using MyFitnessPal.  Disturbingly, 73% of the MyFitnessPal users said that their use of MyFitnessPal had actually contributed to their eating disorder.  

Simply counting calories and trying to stay under some arbitrary target doesn’t end well for most people.  

Why your hunger signals are dysregulated

It’s no wonder many people fall into a binge-restrict cycle when the primary health message is simply to eat less and move more, especially when our hunger signals are dysregulated in our modern food environment due to:

  • artificial colourings and flavours that trick your appetite into believing processed food products contain nutrients that they don’t,
  • processed foods that are a combination of refined carbs and fats which are rare in nature, other than in autumn, and send a signal that we need to build fat for winter, and
  • food advertising associates food with fun cartoons for kids, pleasure, image, social gatherings and popularity rather than providing nutrients and sufficient energy. 

Rather than just trying harder to “build your fasting muscle” by fasting for longer, people who have become obese and/or diabetic need to find a way to get reacquainted with their true hunger signals.  

What is the best fasting schedule for you?  

While fasting continues to grow in popularity, there is still plenty of confusion about the best routine.  

Which one is right for you?  Is it:  

Everyone is passionate about their favourite routine that has worked for them.

  • But how do you know which one is right for YOU?
  • How do you know it’s working?
  • How can you fine-tune your routine to ensure you continue to get results?
  • How do you make sure you’re not going so hard you binge and undo all your hard work?  
  • Then, what if you feel ravenously hungry, but it’s not “time to eat” according to the approach that you happen to have chosen?

Why fasting fails for so many

There are plenty of people who fast for days but are still not lean.  

It’s not that hard to do a multi-day fast, especially if you are carrying a lot of excess body fat.  You feel like a hero as you brag to everyone on Facebook about your high ketones!  

However, there are also plenty of people in the same fasting groups complaining about not making long-term progress as they lose and regain the same few pounds over and over again, often with worsening body composition.  

Rather than occasional herculean efforts, it’s more useful to make incremental changes that build new habits that are maintainable.   

Data-Driven Fasting will empower you to gamify your fasting routine to ensure you move toward your goals over the long term.  Rather than tracking everything you eat to enforce restriction externally, you can turn your weight loss journey and diabetes reversal into a game where optimal weight, body composition, and your health are the prize.  

What is the best food for fasting?   

Where people usually come unstuck with fasting is when they come to refeed. 

“Every fool can fast, but only the wise man knows how to break a fast.”

George Bernard Shaw

After going without food for a few days, you never reach for the chicken breast and broccoli, do you?  

When we feel extremely hungry, we gravitate to the chips, the peanut butter, the nuts, the cream and other energy-dense nutrient-poor foods.  

Related image

Unfortunately, people who fast regularly often end up getting a lot less protein and micronutrients than they need for optimal health, to prevent cravings and achieve satiety to manage their hunger.  In time, they risk becoming ‘skinny fat’.  

There is nothing magical about fasting that eliminates your need for nutrients.   You need to find a way to get enough restriction on a regular basis to achieve the benefits of fasting (i.e. weight loss, reduced blood sugars, insulin sensitivity, etc.) without pushing so hard that your reptilian instincts step in and undo all your hard work!  

Wouldn’t it be great if there was a simple but precise fuel gauge for your body that you could use to tell if you: 

  • actually needed to eat now, 
  • just had a craving for those yummy leftovers in the fridge, 
  • you’re eating out of habit, or 
  • Just because it’s “breakfast time”?

Well, wish no longer.  

I have some good news! 

There is a solution! 

This magic tool is readily available, cost-effective, and you can do it at home as often as you want.  

How to use your glucose meter as a fuel gauge 

The humble blood glucose meter is as close as it gets to having an instantaneous fuel gauge for your body to help you understand whether your hunger is real or if you just want to eat for a multitude of reasons not related to your body’s healthy nutritional requirements.  

While most people focus on how much their blood sugar rises AFTER meals, Data-Driven Fasting uses your blood sugar BEFORE you eat to help you decide if you need to refuel. 

Waiting until your blood sugar returns to baseline ensures you are not over-fueling.  But, waiting a little longer until your blood sugar has dropped below your personalised blood glucose trigger point ensures your intermittent fasting routine is achieving a negative energy balance.  By doing this, you ensure you get all the associated benefits of fasting, like insulin sensitivity, improved blood sugars, weight loss, fat loss, autophagy, etc. over the long term. 

One of the underappreciated secrets of fat loss is that you need to deplete the glucose in your bloodstream before your body can access your body fat.  

If your blood sugars are elevated, you’re not going to be burning as much of the fat from your last meal (let alone that unwanted fat on your bum and belly).

Some people talk about eating more fat to become “fat adapted” so you can be “in ketosis” and burn more fat.  But the truth is, if you want to burn the fat on your body (rather than that fat bomb or second buttered coffee), you need to find a way to deplete the glucose in your bloodstream first! 

Success Stories 

Data-Driven Fasting builds on some previous articles that have continued to receive a LOT of traffic.  We regularly hear from people who have made significant progress as they put these simple techniques into practice.  

Lori used her blood sugar meter

Lori came across the How to Use Your Blood Sugar meter as a Fuel Gauge article in December 2018 and put it into action.  She simply waited until her glucose numbers indicated it was time to refuel, and over nine months she trimmed off 30 lbs.  

As she focused on her blood sugars before meals, her weight came down.  She is now a massive advocate for this approach and has guided many others to success using Data-Driven Fasting.  Lori says: 

I am EVER so grateful for that article.  It gives me a way to know when my body needs fuel, and when I could wait.  

I have a chance to avoid what others in my family have suffered by having high blood sugar (often without even knowing).  

Thank you!  I share that link all over the place!  

I have many friends that are also very grateful to know how they can peel off pounds that seemed persistent and accumulating despite YEARS of effort.

If not for finding your fuel gauge article, I would not be where I am now: at a healthy BMI and with hope for ageing with an excellent healthspan.  

I am glad I can point people to your work.

Lori was on some recent podcast where she described her journey.  If you’re interested, you can listen here and here

We knew we had to create something new to help people who were failing with popular fasting protocols

After seeing so many people struggle to get the results they had hoped for from popular fasting protocols, we figured it was time to create a comprehensive system to help people address the most common pitfalls of fasting.  

And the results of Data-Driven Fasting to date have been very exciting!

So, do you want to learn the secret to making your fasting routine work for you rather than leading to a binge-restrict cycle that is unhealthy for both your body and mind?

If your answer is “yes”, read on.

The secret to burning unwanted body fat 

Our bodies are amazing machines that have adapted to use a wide range of fuels!  The table below (adapted from Cronise et al., 2017) shows the fuels sources that can be floating around in your bloodstream and the order that we tend to burn them.  Oxidative priority is just the fancy term used to describe the order in which each fuel is used.  

While you can only store a little bit of alcohol and ketones, you have more storage capacity for carbohydrates (in your blood, liver and muscles) and a very large (but not infinite) capacity to store energy as fat.

Imagine if you poured crude oil on the ground, petrol on top of it, and lit a match.  The petrol would burn off quickly while the oil may not even ignite.  Oil burns slowly, while petrol burns rapidly.  

Volatile fuels like gas are hard to store.  By contrast, it’s much easier to store large amounts of energy as unrefined crude oil.  The more we refine these fuels, the easier they are to burn.  Similarly, the degree of refining and the macronutrient profile of foods you eat makes the different fuel sources behave differently in your body.   

While your body finds protein hard to convert to energy (most of it is used for muscle protein synthesis or MPS as shown in the table above), it loves to use carbohydrates for explosive activity.  Meanwhile, fat is an excellent slow-burning fuel for storage and everyday use.  

The fact that different macronutrients are harder to convert to usable energy and there are more losses in their conversion is a highly underappreciated food parameter that goes by several names including the thermic effect of food, dietary-induced thermogenesis or the specific dynamic action of food.

Alcohol and ketones MUST be used first because they are highly volatile, and we don’t have much room to store them (other than in our bloodstream).  

Most of us do not overeat protein because it is so satiating.  It is more difficult for our body to convert protein to ATP, so it is a poor source of energy for everyday use.  Your appetite for high protein foods shuts down once you’ve had enough.  

So, our two dominant fuel sources are carbs and fat.  While your body likes to maintain some glucose in your bloodstream, if you have too much, you won’t burn the fat in your blood.  

Because you can only store about 5 g of glucose in your blood (about a teaspoon’s worth), a little dietary carbohydrate can quickly change your blood sugar levels (particularly if your fat stores are already full so you can’t easily absorb the excess energy).  

While we can convert sugar to fat (via de novo lipogenesis), most of the time it’s the fat in our diet that is stored because your body tries to burn off the glucose first and any leftover dietary fat can easily be stored.  

It’s not that fat is a better fuel source than carbs, but it’s the glucose that will show up in your bloodstream and register on your meter after you eat.  Glucose essentially ‘floats on top’ of the fat in your bloodstream and your adipose tissue.  

To access your body fat, you need to deplete both the glucose and fat from your blood first.  

In your body, your fuel tanks are separate but interconnected.  As you deplete the glucose in your blood, it will be refilled from the glycogen stores in your liver (note: glycogen is just the fancy name for the storage form of glucose).  As liver glycogen starts to be depleted, your body will turn to the fat in your blood, and then finally, your body fat.   

You can think of your available fuels as though they are stacked up on top of each other (as shown below).  

blood sugar 
liver glycogen 
free fatty acids in your blood 
body fat 

So, when you measure blood glucose, you are not just measuring the sugar in your blood.  You are really measuring all the fuels stacked up in your body.   

Your Personal Fat Threshold

Although your body fat is your largest fuel tank, it can still become full and overflow.  For reasons we don’t fully understand, some people reach their Personal Fat Threshold at lower levels of body fat.  While most people develop Type 2 Diabetes after gaining weight, some people can develop diabetes while still relatively lean.  

You may have heard the term TOFI (thin on the outside, fat on the inside).  Some people carry their fat on the outside in their adipose tissue (like the guy on the left), while others store excess fat around their organs (like the guy on the right).  

Your body fat acts as a sponge to mop up excess energy (because it is dangerous to have too much in your bloodstream).  But ultimately, just like a sponge can only hold so much water, there is a limit to how much energy your body fat can hold.  

Once you exceed your Personal Fat Threshold (i.e. the amount of energy your body fat can comfortably store), your blood sugars start to rise as excess energy spills over into your bloodstream and get stored in other places in your body.  Fat on the outside of your body may not look great, but it’s the fat on the inside that is dangerous to your health.  

Once your fat stores approach capacity, excess energy backs up and overflows into your bloodstream.  Excess energy starts to be stored as fat around your organs which are now more insulin sensitive than your adipose tissue (which has become resistant to the effects of insulin).   By the time you see elevated blood glucose levels, your body has done everything it can to keep you safe by storing the excess energy from your diet as body fat.   

Having high levels of energy floating around in your bloodstream is not good!  “Energy toxicity” (i.e. too much stored energy to the point that it becomes dangerous) is the fundamental cause of diabetes, metabolic syndrome and most of our modern diseases that are growing at an alarming rate. 

What happens to glucose and fat in your body?

Before we teach you how to use your blood sugar as your personal fuel gauge, it’s crucial to understand how they behave in different situations.  

Your body can use either fat or carbohydrates for fuel.  But we flood our system (so it doesn’t function as efficiently) when we supply it with both carbs and fat at the same time.

Foods that are a combination of both fat and carbs are rare in nature but are the basic formula for modern processed junk food.  We tend to do fine when our food contains mostly one or the other.  

But, given the opportunity, your body loves to fill your carb and fat fuel tanks at the same time.  In days gone by, this was an invaluable survival hack in autumn to help us maximise fat storage to prepare for winter.  However, in our modern food environment when we are always surrounded by hyperpalatable modern foods, it quickly leads to energy toxicity.  

Before you eat a high carb meal, it’s ideal to allow time for the fat in your last meal to be used up.   Conversely, before you have a high-fat meal, it’s ideal to ensure you have used the glucose from your previous meal by ensuring your blood sugars have returned to baseline.  By checking your blood sugars BEFORE you eat you can confirm that the fuel from fat and/or carbs is depleted and you are ready to refuel.  

As you use up the energy in your blood, your pancreas reduces its output of insulin to allow more of your stored fat and glycogen in your liver to replenish the glucose and free fatty acids in your blood.  

You can think of the insulin produced in your pancreas as a dam wall that holds back your energy in storage while you continue to eat.  When you don’t eat, the dam wall (insulin) is lowered to allow your stored energy to flow into your bloodstream.

This chart below shows how different foods raise our insulin levels after we eat.  Notice how glucose (black line) drives insulin up quickly, but after two hours, insulin levels return to baseline.  However, foods that are a combination of fat and carbs like milk (aqua line) have a smaller initial spike, but your insulin levels stay elevated for longer, even beyond two hours.

The fact that your body releases stored energy is the reason that your blood sugar doesn’t go to zero when you don’t eat.  Your liver does a fantastic job of maintaining stable glucose levels by converting stored energy into glucose for release into your bloodstream!  

Your body uses gluconeogenesis to convert protein and even fat into glycogen to refill your liver, so you always have some glucose available when you need it for an emergency.  It’s only when your liver glycogen is depleted that your blood sugar will start to drop, and finally, you will begin to pull more energy from your stored body fat.  

Fat and glucose behave differently  

Using your blood glucose meter as a fuel gauge will work whether you are following a low-carb or a low-fat diet.  However, your blood sugars will behave differently depending on the type of food you are eating.  

Processed junk foods (which are a combination of fat and carbs together) will fill your fat and carbohydrate stores (i.e. glucose in your blood and glycogen in your liver) at the same time.  You can take in more energy before you get a ‘full signal’ from your body and your blood sugars will stay high for longer before you use up all the energy in your bloodstream.

In a recent study, NIH researchers fed 20 participants a 75% fat or a 75% carbohydrate diet for two weeks.  They tracked blood glucose continually and tested free fatty acids in their blood after meals.  

The chart below shows how free fatty acids change after a low-fat meal (green line) vs a high-fat meal (red line).  The fat in your blood decreases more when you consume a high-carb meal, as your liver (controlled by the hormone insulin secreted by your pancreas) slows the release of stored fat into your bloodstream (i.e. lipolysis) until you use up the energy that just came via your mouth.

Conversely, when you eat a high-carb meal (green line), your blood sugars rise for about an hour and then fall back to baseline afterwards.  Meanwhile, we see a much flatter response from a low-carb high-fat meal (red line).  

It’s important to note that if you follow a high fat keto diet or are very insulin sensitive, you may not see as much fluctuation in your blood sugars after you eat.  Some variability in blood glucose is normal and flat line blood sugars should not be your only goal, particularly if it requires a very high-fat diet which can lead to lower satiety, weight gain and increasing waking blood glucose.  

Having a small rise in blood sugars after you eat because you are insulin sensitive (and likely have low fasting blood sugars and a lower level of body fat) is a great thing.  However, if you are more insulin resistant (with high waking blood glucose and more body fat) then switching carbs and protein for more dietary fat only manages the symptom (higher blood sugars after meals) and will not necessarily help you lose body fat and reverse your insulin resistance.  

The bottom line is, If your blood sugars are above your baseline, you still have plenty of fuel onboard.  Regardless of your current cravings, you can rest assured that you’re not going to die if you don’t eat for a little while.   

Whether you are eating high fat or a high carb diet, you want your blood sugars to return to baseline before you eat again.  

Over time, as you eat more than you need to, the average level of both glucose and free fatty acids in your bloodstream will increase as your body fat stores exceed their capacity.   If you are trying to reverse this and lose fat from your body, you want to see your blood sugars trend down.  The little-known secret here is that we can force this trend by waiting for our blood sugar levels to decrease to just below baseline before we eat again.  

While your weight on the scale can bounce around from day-to-day, your blood sugars provide a precise indication of your current energy balance based on your recent food intake and activity.  

How to reduce your fasting blood sugar

Maintaining healthy blood sugar and insulin levels is a big deal, and elevated levels are linked to many diseases, including:

Unfortunately, there has been plenty of confusion and misunderstanding of the role of insulin in our bodies.  Optimising blood sugars, insulin and body fat is not as simple as avoiding carbs and protein to prevent blood sugar spikes after meals.  

Rather than modifying your diet to reduce your rise in glucose and insulin only after meals, you really need to find a way to reduce the average of your blood sugar and insulin across the whole day!  While this may sound similar, the difference in the approach and results is radically different.   

While the amount your blood sugar rises after meals is related to what you eat, your fasting blood glucose level is more closely correlated with your body fat levels, and how much you eat (particularly later at night).  Lots of people focus on trying to manage insulin after meals as the end goal, but inadvertently drive increased insulin levels across the day with a low satiety nutrient-poor diet that leads to increased body fat and subsequently increased hence insulin levels.  

If your waking blood sugar is higher than 100 mg/dL or 5.6 mmol/L, you probably need to lose some body fat to get below your Personal Fat Threshold.  As you work to reduce your blood sugars, you will also use up your unwanted stored body fat.  

Your insulin levels across the day are also closely correlated with your body fat levels.  The only meaningful way to reduce your insulin and fasting blood sugar and reverse Type 2 Diabetes is to reduce the amount of body fat you are carrying.   

Body fat, insulin and blood sugars are highly correlated.  However, while insulin is hard to measure and your weight on the scale can jump around from day to day, we can measure changes in blood sugar throughout the day to understand whether we actually need to refuel at any moment in time.  

By delaying our meals a little longer until our blood sugars are below our personalised trigger point, we can ensure that our body fat is being used for fuel.  Then, once we require less insulin to hold our fat in storage, our pancreas won’t need to work so hard to keep up.  

What is “fasting” anyway?

“Fasting” is simply intentionally refraining from eating for a period of time.  

While Jesus fasted for forty days and nights (Matthew 4:2) and Muslims do not eat during daylight hours for the month of Ramadan, the duration of “fasting” can be much shorter.  

Many of us eat almost continually from waking until going to bed, so an hour or two without food could be considered “fasting”.  We only need to find the minimum effective dose of fasting required to get the results we want.  

Introducing Hunger Training! 

“Hunger training” using your blood sugar as a fuel gauge is an exciting approach that has had some fantastic outcomes in recent studies.  I first came across the idea in a 2012 book, The Glucometer by Angela Ross, where she recommended simply delaying eating if your blood sugar was above 90 mg/dL. 

Later, a 2016 study from the University of Otago in New Zealand, Adherence to hunger training using blood glucose monitoring, found hunger training to be extremely effective, with obese people losing 1.5 kg on average over just two weeks.  

Importantly, they also found it was more effective for people to have a personalised trigger level rather than expecting them to reach what they considered to be an optimal blood sugar before eating.  

People with Type 2 Diabetes and elevated blood sugars had to wait too long for their blood sugars to drop, which made it unsustainable.  The personalised trigger point was found to be much more effective.  

In the subsequent study in 2017 by the same group from the University of Otago, The Effect of Different Types of Monitoring Strategies on Weight Loss: A Randomized Controlled Trial, the researchers tested hunger training against: 

  • daily weighing, 
  • calorie tracking with MyFitnessPal, and 
  • counselling sessions.  

Hunger training using a personalised blood sugar target was the only scenario where people lost weight, while everyone else gained weight!  

Calorie counting using MyFitnessPal saw the largest increase in weight out of the four approaches.  It seems that people lose touch with their actual hunger signals when they outsource their satiety to a smartphone app.   

People did OK when they simply tracked their weight, which made them more mindful of their eating.  However, it was hunger training using pre-meal blood sugars that enabled participants to get in touch with their hunger signals and their actual need for food that led to the best outcome by far!

Notably, the study also found that depression, anxiety and stress all worsened for participants who used MyFitnessPal.  However, these metrics were significantly lower for those who used their blood sugars as a fuel gauge.  

Tracking blood glucose is empowering because it provides immediate feedback.  Understanding your need for food based on your blood sugar gives you a greater sense of control.  When you see a high blood sugar, you can immediately think back to your last meal and understand how your unique metabolism responded.  You quickly learn which meals keep your blood sugars higher for longer and learn to avoid them in the future.  

As shown in the chart below, weight loss was closely related to the number of times participants recorded their blood sugar in the logbook!  

Before too long, participants found they could accurately predict their blood sugars based on their hunger, particularly as their blood sugars started to decrease.  Hunger Training enables is to retrain our understanding of our hunger base on our body’s actual need for fuel!!! 

However, it’s important to note that hunger training had the poorest adherence.  This is not surprising given the imposition of testing blood sugars multiple times per day.  Although incredibly useful, testing blood sugars may not be viable for some people over the long term.  

We have been mindful of this in our design of our Data-Driven Fasting System.  To maximise the chance that you will sustain it long enough to get the result you want, you should only have to track just enough to ensure you are moving forward towards your goal.

The Data-Driven Fasting System

Data-Driven Fasting transitions from an initial three-day period of blood sugar tracking, before and after every meal and snack, to a more relaxed approach where you only test when you feel hungry and want to eat.  Later, if you get sick of testing blood sugars before every meal, you can simply use your waking blood glucose or your scale weight to guide your fasting routine.   

We understand that making this as easy as possible is critical to ensure your long-term success. In the early days, you will learn a LOT about how your body responds to the food you eat, as you calibrate your hunger with your blood sugar…  But the intensity of tracking quickly decreases to the minimum effective dose of monitoring.   

Tracking blood sugars is an excellent option for people who hate measuring their weight.  But you can also use your bathroom scale.   

So, are you interested in learning more about Data-Driven Fasting?

Data-Driven Fasting 30-Day Challenge

After trialling Data-Driven Fasting with more than 300 people… we found that a structured approach was critical to ensure they avoided the common pitfalls and confusion.  So we created the Data-Driven Fasting 30-Day Challenge to help people align your fasting schedule with their unique metabolism, goals, preferences and routine.  

The Data-Driven Fasting 30-Day Challenge will guide you through the following critical elements to optimise your fasting routeing:   

  • Baselining – Find Your Current Trigger that you can use to identify true hunger and when you need to eat to refuel.
  • Your current foods/meals – Learn how the foods you currently eat affect your blood sugar.  Which ones leave you satisfied?  Which ones lead you to eat more than you need to?
  • Hunger training – Learn to delay eating until your blood sugar is below your personal trigger to ensure you eat only when you need to refuel.  This will ensure you are lowering your blood sugars and burning body fat.
  • Curb your late-night binging – Use your waking blood sugars to identify if you are eating too late.
  • Main Meal vs Discretionary Meals – Identify the Main Meal that you will use to anchor your eating routine and ensure you get enough nutrients.  
  • Optimise your eating routine – Lock in your new eating routine which will guarantee you are moving towards your goals.

What you will get:

  • 30-day program to guide you to optimise YOUR fasting routine to ensure you achieve your goals.
  • Data-Driven Fasting Spreadsheet to track your progress and optimise your intermittent fasting routine.
  • 117-page manual complete with detailed instructions and answers to 70 frequently asked questions.
  • A Workbook that you can use to reflect on your learnings.
  • ​Private Community with daily posts and support.  We always find people have more success when they share the journey.

 Join here to get access to your spreadsheet and materials to make sure you’re ready for the next Data-Driven Fasting 30 Day Challenge.  

Phase 1 – Baselining 

This first stage of the Data-Driven Fasting involves checking your blood sugars before and after your typical meals.   

Establish your baseline

This crucial first stage is all about establishing your current baseline blood sugars and identifying your trigger point to help you to determine whether or not you need to eat.

Without changing what or when you eat, all you need to do is measure your blood sugar before your usual meals and snacks for three days.  We also recommend you test your waking blood sugar (after you get out of bed but before you eat anything) and your blood sugar one hour after your meals.  

After you have entered three days of baselining data into your spreadsheet, it will calculate, 

  • your typical waking blood sugar,
  • how much your blood sugars rise after meals, and
  • your typical blood sugar when you feel hungry and want to eat.   

Once you have finished the three days of logging, you will be able to reflect on your blood sugar values calculated by the tracking spreadsheet.  The spreadsheet is colour coded to highlight the highest readings as red and the lowest as green.  You can think of green as good, and you are “go for eating”.

The average of your waking blood sugars for the baselining is shown at the top of the first column (i.e. 4.9 mmol/L in the example below).  

If your average waking blood sugar is higher than 100 mg/dL or 5.6 mmol/L, you are likely above your Personal Fat Threshold, you have some degree of insulin resistance (i.e. Pre Diabetes or Type 2 Diabetes) and you will benefit from losing some weight.  

The top row in the spreadsheet shows your blood glucose rise after the meals you eat.  This will help you understand if your current carbohydrate intake is a problem for you.  If your blood sugar rises by more than 30 mg/dL or 1.6 mmol/L after a particular meal, you probably should avoid that meal in the future (or at least eat less of it next time).  

However, if your rise after meals is less than 30 mg/dL or 1.6 mmol/L, then you don’t need to worry too much about reducing carbohydrates in your diet.  You can get on with focusing on your blood sugar before meals and maximising the nutrient density of the meals you eat.  

It’s also useful to note when your blood sugars rise the most.  Due to reduced insulin sensitivity later in the day, most people find that their blood sugars rise more after dinner and the least in the morning when they are most insulin sensitive.  

If your schedule allows, there are many benefits in moving more of your calories earlier in the day when your body is primed to use the energy from your food rather than store it overnight and keep your metabolism working overtime during the night while you are meant to be resting.  

While you don’t need to aim for perfectly flatline blood sugars, many people experience greater satiety once they reduce their intake of processed carbohydrates and their blood sugars stabilise.  

The spreadsheet will calculate the average of your blood sugars before each meal (i.e. 5.0 mmol/L shown in the example below).  This will be your personalised trigger for the Phase 2 – Hunger Training.  

Get your baselining spreadsheet now

We’re eager for people to find their baseline trigger.  You can download your free baselining spreadsheet here.  

What foods raise your blood sugar the most?

During the three days of baselining, you can also record the foods that you eat and your blood sugars before and after the meals in the ‘foods’ tab of your spreadsheet.  You can then sort this column based on the blood sugar rise after meals to identify the foods that cause the largest rise in blood sugar.   

Large swings in blood glucose make us feel hungry (especially when your blood sugars are falling quickly).  Anyone injecting insulin knows how ravenously hungry they get when their blood sugars go too low.  They want to consume anything and everything to bring their blood sugar back up to normal levels.  So, stabilising your blood sugar is an important first step to gaining control of your appetite (but not the end game).  

Make a note of the foods that cause you to eat more of them or leave you hungry and likely to be raiding the fridge later.  

  • Foods that are a combination of fat and carbs together with minimal protein send a signal to our body that it is autumn, and it’s time to get fat to prepare for winter.  
  • Conversely, foods with a higher percentage of their energy from protein and fibre (like we would find naturally in spring) tend to leave us more satisfied and less likely to overeat.  

We don’t recommend you cut back net carbs to below 15% of calories, as non-starchy veggies tend to be more satiating and nutritious than low carb high-fat foods.  

As shown in the chart below from our analysis of our series of 22 nutrient-dense recipe books tailored for different goals, optimal nutrient density tends to align with around 15% of energy from non-fibre carbohydrates.

Phase 2 – Hunger training

In Phase 2 – Hunger Training, you will start to use your glucose meter as a fuel gauge to help you determine whether you need to refuel or if you could skip that snack or meal you were dreaming of.  

The goal here is not to avoid food for days at a time (i.e. multi-day fasting).  In Phase 2 – Hunger Training, you will simply wait for your blood sugars to drop below your current trigger value before you eat.  As you skip snacks and stretch the time between meals, your blood sugars will start to drift down.  

There’s no need to be a hero.  If you push too hard, you will risk waking your reptilian brain and cause a binge response.  You just need to wait until your blood sugars are below your personalised threshold more often than not.  

There are many reasons we eat

We often eat mindlessly when we’re bored, for social reasons, for entertainment or because it’s “breakfast time”.  However, if you’re trying to lose weight or reverse type 2 diabetes, you should only eat:

  • when you are hungry, AND 
  • require energy based on your blood glucose.  

When you eat, you should prioritise foods with more nutrients (i.e. protein, vitamins and minerals) per calorie (we call this nutrient density).    

In Phase 2 – Hunger Training, you don’t have to test on waking or after you eat.  Just check your blood sugars when you feel hungry and think of going to the fridge, cupboard or cafe.  

  • If your blood sugar is above your personalised trigger value (determined in Phase 1), delay eating and allow your blood sugars to come down a little more.  
  • Wait half an hour to an hour before testing again.  Maybe try drinking some water or some other non-caloric beverage (e.g. black coffee or tea) while you wait.  The feeling of hunger may pass.  
  • Later, if you feel hungry AND your blood sugar is below your current trigger, then go ahead and eat.  For example, if your trigger level is 5.6 mmol/L (100 mg/dL) and your blood sugar drops to 5.5 mmol/L (99 mg/dL) or below, then you’re good to eat a hearty meal if you’re hungry.  

Chasing the moving target – your personalised trigger

Before too long, you should see your blood sugars drop more regularly below your trigger point.  The spreadsheet will calculate your new reduced trigger based on your average blood sugar before meals over the previous week.  

This ‘moving target’ is central to Data-Driven Fasting.  As you progress, you need to continually update your goals and move towards optimal.  You don’t go from couch potato to marathon runner overnight.  You work up to it progressively.  

When you work out in the gym, you get progressively stronger and can lift heavier weights through ‘progressive overload’.  Data-Driven Fasting is like a workout for your metabolism.  You should take it slowly at first.

While it’s not that hard to ‘be good’ for a couple of days, you need to see how you go across the whole week.  Your new trigger won’t be updated until you have consistently logged an average pre-meal blood sugar below your initial trigger (established in Phase 1 – Baselining) for a week.  Hence, you won’t see an updated trigger value until Day 8 of Phase 2 – Hunger Training.   

Meal skipping vs delaying meals  

In the first few days of Phase 2, you will delay eating until your blood sugars drop below your personalised trigger.  Maybe you initially test at 8 am and find you have to wait until 10.30 am for your blood sugar to drop below your trigger.  This is great if you are working from home and can eat whenever you want, but perhaps not ideal in the long term.  

Over time, you should evolve your Data-Driven Fasting routine into more of a ‘meal skipping’ approach.  The spreadsheet will show you how many meals you eat each day based on the number of pre-meal blood sugars you log.   

While you may find you need to eat more on days you are active and fewer meals on others, you should start to see a regular pattern.   Your meal skipping may look something like:

  • If you find your blood sugar is elevated before breakfast, skip breakfast and don’t test again until lunch.  
  • If you had a big breakfast and your blood sugar is still elevated at midday, skip lunch and don’t eat until dinner.
  • If you have a big breakfast and lunch, you may find that your blood sugars are elevated at dinner time, so you will skip dinner.  

Before long, you will see a pattern emerge in your tracking.  Your body likes consistency.  If your eating routine is regular, your lizard brain will remain asleep, happy that it will get fed at a regular time each day.  But if mealtimes are random, your lizard brain will ensure you eat more at each meal just in case the next meal is delayed.   

Eating earlier is typically better than later 

Many people find they binge uncontrollably at night, particularly if they have not eaten much during the day.  Unfortunately, this can lead to poorer food choices and worsening waking blood sugars.  

Due to lower insulin sensitivity later in the day and larger meals at dinner, people typically find their post-meal blood sugar rises more at night.  To help you find the right balance between delaying your first meal and stopping eating earlier, your spreadsheet will flag if your waking blood sugars are increasing and encourage you to stop eating earlier.  

If you find this is the case, you might want to try eating a protein-focused meal earlier in the day regardless of your blood sugars.  You can then treat the other meals as discretionary based on your blood sugar.  

By testing your glucose level before you eat, you will find that you may skip “breakfast” and delay your meals until later in the day.  But by actively managing your waking glucose, you should also work to move your last meal forward.   As you do this, you will find the optimal eating window that works for your routine and your metabolism.  

When to move on from Phase 2 – Hunger Training 

There is no reason that you can’t continue with Phase 2 until you achieve your goal.  You could keep driving your pre-meal target lower towards 4.5 mmol/L or 80 mg/dL (or even lower) if you feel fine and still have weight to lose.   You will continue to lose weight as you progressively chase a lower pre-meal trigger value.   

However, in time, your blood sugars will start to stabilise.  You may get to the point where they don’t drop too much lower by delaying meals.  Someone who has healthy blood sugar levels will have less variability in their blood sugar, particularly if they follow a low carb or keto style diet.  

As you progress towards optimal blood sugar control, the signal to noise ratio from your blood sugars will drop, and hunger training may be less useful.  Factors like your emotions, hormones and activity may start to play a more significant role in the daily changes in your blood sugar compared to your food.  

If you find that testing through the day is too much hassle or your blood sugars no longer vary significantly, we have a couple of other versions of Data-Driven Fasting that you may find useful.  

  • Phase 3.1 – Compress your eating window (fasting blood sugars) 
  • Phase 3.2 – Compress your eating window (weight) 
  • Phase 4.1 – Meal skipping (fasting blood sugars) 
  • Phase 4.2 – Meal skipping (weight)

Each of these approaches is discussed below.  

Phase 3 – Compress your eating window

Most people graze all day, from the moment they wake up to the moment they go to sleep.  Limiting the number of eating opportunities is a great way to let your body have time to access your stored body fat and glucose.  

A 2015 study by Satchin Panda found that 10% of people who ate the least frequently ate 3.3 times per day while 10% of people ate more than ten times per day.  On average, participants met their energy needs for weight maintenance by 6:36 pm but kept on eating until bedtime at 11 or 12 pm regardless.  

They asked people to log each time they ate.  As shown in the ‘feedogram’ below, which shows the time when each participant ate, pretty much the only time we don’t eat is when we are sleeping.   

When participants moved their calorie intake earlier in the day and compressed their eating window from greater than 14 hours to less than 11 hours per day, they found many benefits including improved sleep, reduced body weight and more energy.

Compressing your eating window can be a great hack to avoid overeating.  If you identify as someone who does not eat after 7 pm, you are less likely to find yourself alone with a packet of chips or a jar of peanut butter watching Netflix at 11 pm.

After dinner, your body goes to work digesting the food you ate, uses some of it, and tries to store the rest as glycogen (in your liver and muscle) and body fat stores.  The more you ate yesterday (particularly later in the evening), the higher your blood glucose is likely to be the following day.   

While it’s great to wait until your blood sugar drops below your trigger point before you eat, you also need to keep an eye on your waking blood sugars.  If they are rising rather than falling, you should try finishing eating earlier. 

  • If your blood sugars in the morning are elevated, then bring forward your last meal or skip that late-night snack (e.g. stop eating at 8 pm rather than 9 pm).  Bringing your last meal earlier will allow your body to use up more of the energy in your bloodstream before you wake.  
  • You can also delay your first meal.   If your fuel tank (based on your blood glucose level) is already full, you don’t need to fill up any more, especially if you are not hungry.  

During this phase, we recommend establishing a regular routine. Your circadian rhythm is set by not just sun exposure, but also your activity and eating pattern.  You also likely have a work and family routine that you need to align with.  

Several studies including this one have found that we experience “metabolic jet” lag and tend to put on weight when our mealtimes are erratic (e.g. eating later on Friday night and the weekend than we would during the week or if we skip eating for days at a time and then try to eat “normally” on other days).  

If you know you are going to have dinner with the family at 7 pm, you can treat that as Your Main Meal and structure your other meals around it.  Or perhaps you like a big cooked breakfast, but find it easy to skip lunch?  There are several fasting options you can use based on your preferences and routine.  

For optimal results, we find that people who prioritise the majority of their calories in the morning (i.e. early Time-Restricted Feeding or eTRF) and front load their protein tend to do better in terms of satiety.  This is not a showstopper if you can’t make your first meal your largest.  But if you find that you are overeating in the evening, shifting the bulk of your calorie intake to earlier in the day may help to reduce your overall daily intake.

As shown in the chart below from our analysis of half a million days of MyFitnessPal data, people who eat only breakfast and lunch tend to eat less across the day.  Avoiding overeating too late and prioritising the first meal of the day seems to be ideal.  

Some people find they are not hungry in the morning, but this is likely because they ate a big dinner.  Once you skip dinner a few times, you’ll quickly find yourself hungry in the morning and fall into a new routine soon enough.

Each day, record your waking blood glucose levels and the time of your first meal (black tea and coffee don’t count) and your last meal.  The spreadsheet will calculate your eating window and give you recommendations to try to compress your eating window a little more.  

There are two Data-Driven Fasting options to help you dial in your eating window.  

Phase 3.1 – Compress your eating window (fasting blood sugars) 

In this option, you will test your blood sugars each morning.  If your waking blood sugars are above your average, you will try to compress your eating window a little.  

Over time, your eating widow will tighten until you find a routine that allows you to continually reduce your waking blood sugars.  As you do this, your weight should also reduce, and your blood sugars during the day will stabilise.  

Phase 3.2 – Compress your eating window (weight) 

In this option, you simply weigh yourself each day (no blood sugar testing required!).  If your weight is above your target, you tighten your eating window until you find a routine that allows you to maintain your target rate of weight loss. 

You can choose a gentle rate of weight loss of 0.5%, which is more sustainable if you don’t have a lot of fat to lose.  However, if you are feeling ambitious, you can choose up to 2.0% per week.  

In our 6 Week Nutritional Optimisation Masterclass, we see many people able to achieve 2.0% per week weight loss per week if they have their nutrition dialled in.  However, if you find you are not able to achieve this or are experiencing excessive hunger that leads to rebound bingeing on poor quality food, we recommend dialling back your target.  

Phase 4 – Meal skipping 

Rather than thinking in terms of an eating window, it can be more useful to simply limit the number of times you eat each day.  In Phase 4, you can use either your daily weight or your waking blood sugar as a guide as to whether you should have one less meal than usual today.  

While it’s nice to have a tighter eating window to help you manage your food intake, limiting the number of times you eat a day will achieve the same result, potentially with less hunger.  Meal skipping is also a great way to manage your energy intake without tracking calories.  

Varying the number of times you eat each day can give you more time in a calorie deficit when insulin is low, and your fat stores are being used.  If your waking blood sugar is above your average or your weight is not dropping in line with your target, you can simply “turn off” one of these eating opportunities which will reduce your calorie intake for that day.

Phase 4.1 Meal skipping based on waking glucose 

This approach is ideal if your waking blood sugars are still above optimal levels.  In this version of Data-Driven Fasting, you will eat one fewer meals than usual if your waking blood sugar is above your current average.  For example, if you typically eat four times per day, you would eat only three times on days that your waking blood sugar is above your current average in the morning.  

Phase 4.2  Meal skipping based on your weight 

This version of Data-Driven Fasting uses your daily weight as a guide as to whether you should skip a meal today.  This approach is ideal if your blood sugars are closer to optimal, but you still have weight to lose.  

In your spreadsheet, you set a weight loss target and fat loss target.   If your weight is above your target in the morning, then skip a meal today.  It doesn’t matter too much if you are skipping breakfast, lunch, dinner or your after-dinner snack.   

Let’s say you have three meals and an after-dinner snack.  If your weight is above your target, you will simply skip a snack that day.  If your weight drops below your target the next day, then you can have your snack again, if not then you’ll skip it tomorrow too.  

This will force you to be more mindful and intentional as you plan your meals.  Over time, you may go from three meals and two snacks to three meals and then two meals with a smaller eating window.   

Phase 5 – Maintenance 

Congratulations! You’ve arrived at your goal weight!  From here, we recommend you continue to weigh yourself and take your waist measurement weekly.  If you find your weight or waist drifting back up, you can jump back into your preferred method until your weight comes back into line.  


  • Intermittent fasting is a useful way to manage our energy intake without tracking calories.  
  • By measuring the most useful parameters (e.g. blood sugars, weight, body fat and waist), you can ensure you are getting the minimum effective dose of restriction to ensure you move towards your goal (e.g. weight loss, fat loss, diabetes reversal, longevity, etc.).
  • Extended fasting can lead to dysregulated appetite signals and refeeding on energy-dense nutrient-poor foods.  Due to this, despite their restriction and deprivation, many people do not see progress over the long term.  
  • Hunger training uses our blood sugars to verify whether we need to refuel or not and whether our hunger is real.  By waiting to eat until our blood sugar is lower, we draw down our excess glucose and body fat stores.  
  • We can also use our blood sugars or our scale weight to refine our eating window as well as identify when we need to skip meals to ensure our weight loss continues at the desired rate.  

Here’s some we prepared earlier 

Since we initially published this article, we’ve seen some great results!   


Sue has already lost a significant amount of weight through optimising her nutrition and intermittent fasting (you can read about her journey here).  Still, she was eager to try Data-Driven Fasting to optimise her routine further.

The image below shows her baselining blood sugars, with an initial trigger value of 5.1 mmol/L after her previous weight loss.

After the three days of baselining she launched into hunger training and has been able to lose 4.7 kg (or 9% of her body weight) in 50 days, with her trigger value dropping from 5.1 to 3.9 mmol/L as she transitioned from four meals a day to typically two meals per day.  

While there were some blips in her weight with different celebrations and weekends away with more indulgent eating, she was able to get back on track.  

As shown in the charts below, her weight loss was all fat.  

With some attention to good nutrition and some resistance training, she was able to gain lean mass, even at 70 years of age!  

As you can see in the charts below, as she chased a lower blood sugar target, her weight and body fat followed.  

The relationship between premeal glucose trigger, weight and body fat are highly correlated!  

Nice work Sue!  We’re super proud of what you have achieved with Data Driven Fasting


In just over four weeks Saskia dropped 3.8 kg (5% of her weight) and 2.7% body fat in less than three weeks.  Saskia found her blood sugars rose around ‘that time of the month’, however afterwards things settled back down, and her weight and fasting glucose continued their downward trend.  Saskia says, “I was eating well, but was gaining weight because I had the same routine for ages.  This has totally shaken things up.  It’s the best new thing out there!”  


In a couple of weeks, Tim has seen his trigger drop from 5.3 to 4.8 mmol/L as he lost 6.6 lbs.  Tim said, “It’s the easiest 8 lbs I’ve ever lost.  Zero feelings of being deprived.”


Tammy has been seeing some great progress with 5.8 kg weight loss and a reduction of 3.2% body fat, with her trigger quickly dropping from 5.3 to 4.0 mmol/L.  She initially tried OMAD in the evening but recently switched to OMAD at lunch and has seen her weight loss progress and her waking blood sugars decrease.  

She’s also making some great progress in terms of fat loss without losing lean mass.   


After using her blood glucose as a field gauge for two years, Lori is now maintaining her trigger value of close to 80 mg/dL with an optimal waking blood sugar of between 90 and 100 mg/dL.  

Frequently Asked Questions and Pro Tips

We’ve compiled some answers to frequently asked questions that people have asked in the Data-Driven Fasting Facebook Group as they have trialled the system.  If you have any other questions that aren’t covered or see anything else that you’d like clarified, feel free to join the Data-Driven Fasting Facebook Group and ask away.

1. What things affect blood sugar levels?

As noted by Dr Jason Fung (author of The Complete Guide to Fasting) in the Optimising Nutrition group four years ago when we were developing Data-Driven Fasting, many things can affect your blood sugars, such as stress, exercise, illness or hormones (e.g. that time of the month for women).  

Don’t be too hard on yourself if you feel compelled to eat before your blood sugars drop below your trigger.   Just observe the relationship between your hunger and your blood sugars, stress, sleep and mood.  

The intent of Data-Driven Fasting is to use your blood sugars as a guide.  There will be times when you choose to eat, even if your blood sugar is above your trigger.  This is normal.  You don’t need to beat yourself up over it.  You only need to wait until your blood sugar is below your personalised trigger point more often than not to see progress over time.  

If your blood sugar is above your trigger and you are hungry, and you chose to eat, you may want to try to eat a little less or prioritise nutrient-dense foods and meals with a higher protein percentage.  

2. Which blood sugar meter should I buy? 

If you don’t already have one, there are some nifty high tech and cost-effective blood sugar meter options available.   

In Australia, blood sugar testing strips are subsidised by the National Diabetes Services Scheme, and the cost of the meter is often free or reimbursed (because they make their money off the strips after you buy the meter).  

Depending on your location and health care cover, your doctor may prescribe one so you can get it more cost-effectively or it may be covered by your health fund.   

Until recently, the FreeStyle Lite was my favourite meter as it is compact and accurate.  It only needs a tiny amount of blood, so the tests are pretty much painless.  However, while it will connect to your computer to download the data, it’s not particularly high tech.

A more advanced meter option is the Contour Next One, which has a smartphone app that helps you analyse your data.  It’s everything you’d hope a modern blood sugar meter would be!  You can enter your targets and make notes on the phone as soon as you take the measurement.  It’s also extremely accurate.  

Rather than having the spreadsheet open all the time, you can make notes in the app and then transfer them to the spreadsheet on the weekend to calculate your updated trigger.  You can even add photos of your food in the app.  

Once you program the app with your target, it gives a happy flashing green light when you are below your trigger.  You can get a nice little dopamine hit from the green light rather than less than optimal comfort foods.  

If you’re in the US and looking for a cheap meter, then the Walmart Relion is a good option.   But if you have the funds and find Data-Driven Fasting useful over the long term, it may be worth investing in a more accurate and reliable option.  

3.  Would a continuous glucose meter be better?

There is a host of continuous glucose meter (CGM) options.  The Dexcom G6 is the gold standard for Type 1 Diabetes management and sends a reading to your phone or other devices every five minutes to give you alerts.  

The Freestyle Libre is also awesome, and a little bit cheaper, but requires you to swipe the reader (or your phone across your monitor).  

However, a CGM may be excessive for what we are trying to achieve with Data-Driven Fasting.  If you’re looking to avoid the (little bit of) pain of testing, keep in mind that CGMs are not painless to insert.  CGMs are also not cheap over the long term!  

The goal of Data-Driven Fasting is to retrain your appetite by checking blood sugars.  If you can see your current blood sugar all the time, you’re more likely to eat BECAUSE your blood sugar dropped below your target (even if you’re not hungry).  

Your liver will release glucose from storage into your bloodstream to keep your blood sugars stable, and your blood sugars may even rise in anticipation of food.  Some people have found that they check their CGM when they’re hungry, and later find that their blood glucose has risen by the time they have prepared their meal and are ready to eat.  This can be confusing.  

The goal of hunger training is simply to check that your glucose has dropped below your trigger point when you are hungry and hence you are starting to deplete your glucose and fat stores.  It is not to continually re-fuel ever time your blood sugar drops even if you’re not hungry.  

The study Comparison of finger-prick blood glucose testing vs CGM technology in hunger training found that people using CGM tested more regularly, but recorded their glucose less frequently.  Both groups lost similar amounts of weight using hunger training.  

So, a CGM is great if you already have one or you’re a cashed-up biohacker data geek, but a CGM is not going to be better for our purposes.  There are also benefits in the small hassle of doing the finger prick and recording your blood sugar before you eat.  

4. How does exercise impact your blood sugar levels?

Taking a moderate paced walk or doing some low-intensity exercise will deplete your blood sugar.  

But be aware, if you do intense exercise, your body will release glucose into your bloodstream to fuel the activity.  This is not a problem, just something to be aware of if you happen to test your blood sugars after exercise.  

People often don’t feel hungry after exercise because of this elevated blood sugar effect.  However, if you do feel hungry after your workout and your blood sugar is still artificially elevated due to the exercise, don’t be afraid to eat.  You may find that eating before or after your workout helps you avoid more intense hunger later in the day (which often leads to poorer food choices).    

If you do a heavy workout (e.g. high-intensity interval training, heavy squats or deadlifts that deplete glycogen stores) don’t be surprised if you find yourself hungrier later in the day as your body tries to refill your glucose and fat fuel tanks.  You can experiment with your meal timings to ensure you refuel before your blood sugar gets too low, and you end up in an all-out binge.  

It’s impossible to accurately calculate the calories you burn during exercise.  It’s also easy to overeat due to increased hunger after your workout.  However, once the initial glucose surge has dissipated, your blood sugar will give you a good idea whether you are over or under-fueling over the long term. 

5. How does sleep affect your blood sugars?  

Getting good sleep is essential, especially when it comes to managing your cortisol and waking blood sugars.  Don’t underestimate the power of a good night’s sleep to stabilise your glucose and help you manage your appetite.  

We tend to sleep better if we’re not over full or too hungry.  Ketone levels rise after a long period without food to ensure you are energised to go out and hunt rather than lie down and have a deep sleep.  

Try not to eat a big meal just before you go to bed, otherwise, your metabolism will be elevated through the night.  At the same time, you don’t want to be too hungry.  

6. Why would my glucose increase when I don’t eat?

It may seem counter-intuitive, but your blood glucose after meals or upon waking can increase as you start to lose weight, especially if you don’t have excellent metabolic health or have a lot of weight to lose.  

It’s as if your body has a lot of stored energy to unload and is eager to dump extra glucose and fat into your bloodstream as soon as you cut back on your food.  While our goal is to reduce blood glucose, especially in the morning, as a sign of good overall metabolic health, keep in mind that when you are losing weight, your body is not in a steady-state.  

If your insulin levels suddenly drop, you may start dumping a lot of energy into your bloodstream.  If your other markers (e.g. body fat, weight and waist) are moving in the right direction, then there is a good chance you will be in a much healthier position in the longer term once things stabilise.  

Eventually, though, you will deplete your liver glycogen, and you should see your blood glucose levels come down as your body fat levels decrease.

7.  How should I adjust my diabetes medications when I start fasting?

Medications such as injected insulin will help to manage the symptoms of type 2 diabetes (i.e. elevated blood sugars), but do little to reverse the underlying cause (i.e. energy toxicity), and can make it harder to lose unwanted body fat.  

Injected insulin forces your body to hold fat in storage and can make you hungrier, which can lead to weight gain.  As you lose weight, you will see a reduced need for both injected basal and bolus insulin due to improved insulin sensitivity as you start to lose excess body fat.  

If you are taking any diabetes-related medications (especially injected insulin) you should pay particular attention to your blood sugars as you extend the time between meals and work with your health care team to adjust your medications to ensure that your blood sugars don’t go lower than you feel comfortable with (e.g. below 4.0 mmol/L or 72 mg/dL).  Not only will you feel unwell below this level, but you will also want to eat anything and everything until your blood sugar returns to normal.  

Maintaining a predictable routine is extremely important.  If you radically change your eating pattern (e.g. skipping a whole day of eating or multi-day fasts) your insulin needs will plummet, and you will risk hypoglycemia (low blood sugars).   

In Phase 2. Hunger Training, you will make incremental changes to your eating routine, which will allow you to slowly dial back your insulin.  While it’s ideal to maintain lower blood sugars, it may be wise to progressively back off your insulin dosing and allow your average blood sugars to run a little bit higher until you develop a consistent routine and reduce the variability of your blood sugars.   As demonstrated in the CGM charts below, once your glucose variability reduces, you will be able to dial in your insulin dosing to maintain lower average blood sugar. 

8. How can I integrate fasting into my normal routine?

Try to fit your fasting schedule around your regular work and family routine.  If you typically eat dinner with the family, then you ideally wouldn’t skip that meal (even if it’s your only meal of the day).  You can then treat the other meals as discretionary using your blood sugars as a trigger for them (and not your family dinner).   

9.  Follow the trend, ignore the noise

The benefit of using a data-driven approach to guide your fasting is that you ensure you get what you want out of the process in the long term.  Before long, you will learn to fine-tune your eating pattern to your requirements, appetite, activity and schedule.  

The chart below shows an example of how blood sugars can tend to decrease in our Nutritional Optimisation Masterclass.  While there is plenty of scatter from day to day, we see a trend over the longer term.

This next chart shows the weight of the same person for the same period.  As blood sugars decrease, weight also decreases.  Again, the data can bounce around from day to day, but there is a definite trend. 

While it’s useful to track body fat to ensure you’re losing fat and not too much precious lean muscle mass, you should be aware that body fat data can be even noisier.  But, as we force the blood sugar trend in the direction we want it to go by delaying or skipping meals, we will see weight and body fat trend down.

As much as you can, simply record the data and follow the recommendations without overthinking it.   You need to accept that there will be some days when the data doesn’t go your way for no apparent reason.  However, your focus needs to remain on managing the long-term trend, not the short term fluctuations.  

Feel free to use your brain to decide whether or not you need to eat even if your blood glucose is above your trigger.  While more compliance is better, you only need to wait until your blood sugar is below your trigger value more often than not to achieve a downward trend over the long term.

10. Hunger is not the enemy

With Data-Driven Fasting, you will get to know your hunger, not ignore it.  You will grow to understand your hunger by giving it some attention until you understand it, and it will be your friend.   

The goal of hunger training is to train your body to get used to lower blood sugars and a small amount of hunger.  While extended fasting can lead to dysregulated hunger signals, Data-Driven Fasting will help you gain a better understanding of true hunger.  

As your blood sugars stabilise, your body will become more comfortable with a small amount of hunger.  Soon, that little bit of hunger will no longer be uncomfortable.   You will ‘train’ your appetite and hunger signals to a new normal.  Your lizard brain will become comfortable with a lower level of energy in your bloodstream.

11. The psychological impacts of data-driven fasting 

The goal of Data-Driven Fasting is to become more attuned to your hunger signals.   

While testing your blood sugar may sound like a hassle, a tiny amount of pain and inconvenience from the blood sugar tracking is not such a bad thing because it forces you to be more mindful and question whether you need to eat.  It interrupts habitual mindless eating and adds a quantitative check to see if you need to refuel.  While many people find that calorie counting harms their mental health, Data-Driven Fasting puts you in control of your hunger and appetite with a precise fuel gauge.  

Like a roulette wheel or a slot machine, a little bit of measurement gamifies the intermittent fasting process as you wait for the green light on your blood glucose meter.  There is a little bit of luck (due to the many factors that affect weight and blood sugars) and a bit of skill involved (i.e. managing your eating routine and food choices).  But the prize is excellent metabolic health (not to mention looking and feeling great).  

12. Progress over perfection

Remember, your goal is progress, not perfection.   Blood sugars can vary for a range of reasons.  You don’t have to be militant about not eating if your blood sugars aren’t dropping and you are starving hungry.  

If you have a bad day, that’s OK.  You will learn something, and you can always catch up.  The goal is to be below your trigger point more often than not before you eat.  If your blood sugar is slightly above your trigger and you’re ravenously hungry then don’t be afraid to eat, especially if you have eaten fewer meals than usual today.  It’s not absolute black/white or good/bad.  

Your glucometer is simply a tool to empower you with knowledge about whether you need to refuel, not to make you feel like a failure or wracked with guilt.  Hunger training using your blood glucose as a fuel gauge simply provides you with the information you need to understand if your hunger is real, and you need to eat.  The process will be more sustainable if you don’t lose your mind in the first few days trying to be perfect.  

You should approach this as a curious student, eager to learn how your body responds to food.  Data-Driven Fasting will help you realise the impact of those “bad days”.  Before long, the “bad days” will become less frequent.  You will quickly learn that overeating and/or poor food choices will have a downside in the future, so you will learn to moderate your meals today. 

Your goal is to develop a healthy relationship with food.  Feel free to stop if you feel you are becoming obsessive or it is consuming too much time or mental energy.  While some people love quantifying everything, others can quickly become overwhelmed.  We have designed Data-Driven Fasting to minimise the cognitive load as much as possible.  

If you feel ravenous, grumpy, light-headed and you can’t think straight, you have a report due or an important meeting, don’t be afraid to eat.  You can always catch up by skipping a meal tomorrow.

The goal is to gamify mindful eating using the most effective and useful data available.  Rather than relying on an external calorie counting app to tell you whether you are eating too much or too little, you are using your internal fuel gauge (i.e. your blood sugars) to tell you if you need to eat.  

As you start to skip snacks and delay meals, you will learn to become comfortable with a little bit of hunger.  You may also feel a lot more satisfied when you do eat.  

13. How do I stop snacking at night?

One possible scenario with Data-Driven Fasting is that you will eat a big dinner, check your blood sugar in the morning and find it is above your trigger, so you will delay eating until your blood sugars come down in the afternoon or before dinner.  But, later that evening, you find you are even more hungry at night and have less controlled eating and find yourself bingeing again.  This is particularly a concern if you see your waking blood sugars increasing.  

If you are reaching for energy-dense foods because you are too hungry after not eating all day, we recommend you try having a more substantial protein right meal earlier in the day, so you are less hungry at night, and therefore less likely to binge on energy-dense nutrient-poor food.   

If you are finding that you are overeating because you are skipping meals earlier in the day, you might even want to reset your trigger a little higher, so you can eat earlier in the day or give yourself a little bit more leeway to eat.  Another option is to lock in breakfast or lunch as the meal you will eat every day and then use your blood sugar trigger to decide if you will eat the other meals.

Our data analysis suggests that we tend to eat fewer total calories if we spread our food out over two meals rather than one compressed eating window.   

However, if you find that OMAD works for you, that’s fine, so long as you can get adequate nutrients in your compressed eating window (particularly protein).  You may find you alternate between one and two meals per day.  

14. Front-load your protein to hack your satiety

Our data analysis also shows that people who eat more protein at their first meal of the day tend to eat a lot less across the day.  So, do what you can to make sure your first meal is “hearty” with plenty of protein (e.g. steak and eggs, not a Bulletproof Coffee or croissant).   

Perhaps you could eat a big breakfast before work with plenty of protein and have a small lunch or skip lunch at work and have dinner with the family once your blood sugars drop.  

Or maybe you have coffee first up (black or with just a dash of milk or cream) and eat a large cooked meal in the middle of the day and then a moderate dinner with the family after work.  

Try to find a routine that works for you that allows you to eat in a controlled manner and avoid ravenous late-night hoovering of everything in the fridge.  

15. Three steps forward, one step back 

Don’t be surprised if you find yourself ‘backsliding’ occasionally.  Weight loss is rarely a linear process.  It’s also natural to follow a fasting and feasting cycle that ebbs and flows with the varying needs of your body.  

If you find yourself really hungry, there is no need to be ashamed of eating to satiety, especially if you maintain a focus on nutrient-dense whole foods.  As you follow the process, you will iron out the kinks in your routine and ensure a long term trend towards your goals.

16. Should I test ketones when fasting?

As you fast for a longer period, your blood sugars will decrease, and blood ketones (BHB) increase as your body starts to burn stored fat for fuel.  This chart shows my blood glucose and ketone values during a seven day fast.  You can see blood sugar slowly trends down over time while ketones rise.  

After not eating for days, ketones can get quite high.  However, in the first few days, they don’t rise that much.  But, you don’t need high ketone readings to be burning body fat.   

In fact, as your metabolic health improves, you may even see your ketone levels decrease as the level of total energy in your bloodstream decreases (i.e. from fat, glucose and ketones).  In our Nutritional Optimisation Masterclass, people tend to see their blood ketone values increase for a few weeks and then decrease as they begin to burn their body fat.  

Virta’s study results also showed that, after an initial period of high ketones in the first few weeks, over the long term blood ketones return to baseline as people lose weight and reverse their diabetes.  The ketone values were much lower than are typically believed to be ‘optimal ketone levels’.  When it comes to blood ketones, more is not better.  

If your goal is to burn body fat, it’s a good thing to have lower blood glucose and higher ketones (this is known as the glucose:ketone index).   

It’s also useful to note that blood ketones are the storage form of ketones, while breath ketones (i.e. breath acetone) is a more meaningful indicator of whether you are burning ketones (rather than forcing them to build up in your bloodstream).  Check out this article for more details on breath ketones if you’re interested.  

Testing blood ketones is not necessary.  It doesn’t tell you much in addition to lower blood sugars.  Ketone test strips can also be expensive, and the test results are hard to interpret.  So, unless you are just curious because everyone else is doing it and you have some excess cash to burn, save your money and skip the ketone tests.  

17. Why am I not losing weight?

If you are eating one or two meals a day and waiting until your blood sugars drop below your trigger point but still not losing weight, then it’s likely that you’re simply loading a LOT of calories into fewer meals.  

When fasting, what you eat is still critical!  In fact, food quality becomes even more critical when food quantity is reduced.  Don’t underestimate your reptilian instinct’s ability to outsmart your conscious brain to keep you alive, especially when you try to starve it.   

If you push your body too hard, your cravings for energy-dense foods will increase to enable you to get more energy in the compressed eating window.  Some people who eat a high fat keto diet with plenty of body fat to lose see their waking blood sugars remain elevated while their daytime blood sugars are lower and stable, and so don’t get a useful signal from testing their blood sugars.

To understand if this is the case for you, it may be useful to track your food intake for a few days in Cronometer to check the macronutrient split of the food you are eating.  To also check the micronutrient content of your food and find out which foods and meals you should be eating to achieve a balanced diet at a micronutrient level, we recommend our free 7-day Nutrient Optimiser Tracking Challenge.

Our analysis of 60,000 days of data from Optimisers shows that foods and meals that contain a higher percentage of protein are very hard to overeat.  People who are getting closer to 40% protein experience greater satiety and effortless weight loss, whereas people who are getting closer to 15% protein struggle to lose their unwanted body fat.  Some people refer to this as ‘fuel pulling’ (where you pull glucose and fat from your body rather than your food), a Low Energy Diet or a Protein Sparing Modified Fast.

It’s easy to pack a lot of energy into your meals if they contain a lot of carbs and fat with less protein.  This is the basic formula for modern junk food.  Given the opportunity, your body will always choose the low protein energy-dense foods that allow you to consume more energy and store more fat for the coming winter.

Many people who fast choose to refuel on foods with a higher percentage of energy from fat, believing in eating ‘fat to satiety’ will lead to weight loss.  Unfortunately, this approach just makes it easier to consume more energy.  If you want to use the fat on your body as fuel, you need to manage the fat in your diet.  

Eating fewer meals and getting less protein is not ideal in terms of satiety or achieving optimal body composition.  Before focusing on nutrient density, in our Nutritional Optimisation Masterclass, we initially guide people to ensure they are getting adequate protein and then trim back the energy from carbs and fat to align with their goal.  

As shown in our analysis of our 22 recipe books, foods with a higher percentage of protein tend to have a higher nutrient density.  Focusing on nutrient-dense foods when you eat is incredibly important, particularly if you are trying to eat fewer meals.  

Our series of 22 recipe books are designed to help you dial in your macros and micros without tracking.  

We are super excited about these, and we have seen some stunning results already.  

18.  What if blood sugar testing is getting too expensive or painful?

While using your blood sugars is the best way to understand if you need to refuel, over time you may find testing becomes expensive (particularly if your test strips aren’t covered by insurance or rebates), too painful, or hard to do consistently.  If you find this is the case for you, there are several options.

  • Make sure you wait until you are actually hungry to test.  Over the first week or so you will get a feel for when your blood sugars are lower, testing will be less of a novelty, and you will tend to test less regularly.  If you’re only eating two or three times a day, you only need to be doing two or three tests.  
  • Rather than eating haphazardly based on your blood sugar, it’s ideal to have regular meal timings.  After a few days of Data-Driven Fasting, most people find they eliminate snacking and drop back to two or three meals a day with a regular schedule.  If you typically have three or four meals per day and you find your blood sugar is elevated before you eat one of those meals, simply skip that meal and don’t test until the next normal meal.  
  • If testing two or three times during the day is still too much hassle, expense or pain then you can skip to Phase 3.1 (compressing your eating window if your waking blood sugars are above your average) or Phase 4.1 (have one less meal today if your waking blood sugar is above your average).
  • If you’re completely fed up with testing your blood sugars, you can use Phase 3.2 (which involves compressing your eating window if you are not meeting your weight loss target) or Phase 4.2 (have one less meal if you are not meeting your weight loss target).  

19.  Are there any added benefits from extended fasting?

While there may be benefits of extended fasting (e.g. no food for three or more days), there are also downsides.  Not many people enjoy not eating for days on end, and it can be hard to fit into a regular family routine.  

Even fasting gurus admit that we don’t know what length of fasting is required to achieve benefit minimum effective dose and meaningful results.  Is it 24 hours?  36 hours?  Three days?  Seven days?  Or maybe fourteen days to get the?  

Unfortunately, extended fasting does little to teach you to eat well when you do eat, and may lead to reduced diet quality, fat gain and muscle loss over the long term.

If you are not able to control food quality when you refeed, you are trying to fast for too long and are unlikely to be making sustainable long term improvements.  The good news is that most of the benefits of extended fasting can be achieved by dialling in your daily meal routine to ensure a long-term energy deficit that leads to optimal body composition.   

Data-Driven Fasting will guide you to optimise your meal timing and enable you to focus on getting the nutrients you need with a sustainable routine over the long term.  

While people get excited about the benefits of fasting for autophagy, cancer and Alzheimer’s, what we do know is that all of these conditions are vastly improved by maintaining more optimal body composition.  

As shown in the chart below, the relative risk of a range of cancers increases with increasing our Body Mass Index (from Quantitative association between body mass index and the risk of cancer: A global Meta-analysis of prospective cohort studies: Obesity and cancer risk).   

The images below (from Waist-to-height Ratio Is More Predictive of Years of Life Lost Than Body Mass Index) show that our overall mortality risk increases with a higher BMI and waist to height ratio.

Rather than asking “How many days should I fast for?” what you really need to know is, “How can I optimise my normal eating to ensure that I am moving towards a more optimal body composition and staying below my Personal Fat Threshold?”

20.  How do I know if I’m below my Personal Fat Threshold?  

While weight and body fat are what most of us focus on, being below your Personal Fat Threshold is arguably more important.  

But how do you know if you are below your Personal Fat Threshold?  

As you can see from the chart below (from Association between fasting glucose and all-cause mortality), the lowest overall risk of dying from any cause (aligns with a fasting glucose of less than 100 mg/dL (or 5.6 mmol/L) and between 80 – 90 mg/dL (or 4.4 to 5.0 mmol/L).  

This next chart from the same study shows that the same relationship applies, regardless of age or gender.   

If your waking blood sugars are in the optimal range, it means:

  • you are insulin sensitive, 
  • your insulin levels are low, 
  • your body fat can absorb extra energy your food, and 
  • you do not have excess energy backing up into your bloodstream.  

Below 25% body fat for women and below 15% for men is excellent.  A waist to height ratio of less than 0.5 is ideal for both genders.  Pushing significantly below these levels may not be healthy or sustainable.  However, your fasting blood sugar is an even better indication of whether you are experiencing ‘energy toxicity’.  

We recommend you continue with Data-Driven Fasting until you achieve an average fasting blood glucose of less than 100 mg/dL (or 5.6 mmol/L) and ideally less than 90 mg/dL (or 5.0 mmol/L). At this point, you can be assured that you are working within your Personal Fat Threshold.   

21.  When should I test my blood glucose after eating?

Many people ask when they should measure their blood sugars after a meal.  The answer depends on what you are eating and your unique metabolism.  

As shown in the chart below, blood sugars rise quickly after a high carb low-fat meal (green line) while they will increase more slowly (and not as much) after a high-fat meal.  Testing one hour after you eat is a good rule of thumb, but you could do some extra testing (e.g. every half hour for two hours after a couple of meals) to find out when your glucose levels peak with your typical meals if you’re curious.  

All we are trying to do in the baselining phase is: 

  • find which meals raise your blood sugar the most (and which ones you might need to avoid in the future),
  • identify when you are most insulin sensitive vs insulin resistant (e.g. if your blood sugars rise the most at night and less in the morning you might benefit from shifting your meals earlier), and 
  • understand if you need to worry about carbs raising your blood sugar or if you should just be focusing on more satiating nutrient-dense foods and meals.  

While higher fat foods will cause a smaller rise in blood glucose, you need to find the balance between getting adequate nutrition and stable blood sugars.  As shown in this chart from our analysis of our series of recipe books, very high-fat foods tend not to be as nutritious.   

While the blood sugar rollercoaster is bad, flatline blood sugars are not the end goal.  Stable blood glucose levels are a symptom of good metabolic health.  While we can achieve stable blood sugars with a low carb high-fat diet (i.e. manage the symptom), diabetes reversal and improved metabolic health require reduced body fat levels.  

 So, when testing your blood sugar after meals, keep in mind that:

  • fast-acting carbs will raise your blood sugars quickly, but they may also come down quickly, 
  • high-fat meals will help you achieve more stable blood sugars, but they may stay elevated for longer before you are ‘allowed’ to eat again, and 
  • meals that are a similar proportion of fat and carbs with low protein (e.g. cookies, croissant, milk chocolate, etc.) will fill both your fat and glucose stores and keep your blood sugars elevated for longer.

22.  How does that “time of the month” affect blood sugars for women? 

Females of reproductive age should be aware that cravings and insulin sensitivity will vary across the month.  

Women with Type 1 Diabetes find that their insulin requirements increase by 10 to 15% in the days leading up to their period and then drop sharply, while insulin tends to be lowest in the middle of the cycle around ovulation.  Other women find that their blood sugars are more elevated during their period.  

Cravings and water retention (along with associated water weight gain) also tend to increase.  So, if it’s “that time of the month”, you may need to be more gracious when it comes to waiting for your blood sugar to drop below your current trigger.  You may want to accept a slightly higher trigger value or default to your typical eating routine and just eat when you are hungry during this time.   

23.  What is a “good” trigger value? 

We find it interesting to see how we compare with everyone else to understand how far we have to go to catch up with others who are closer to optimal.  

The charts below show trigger values during baselining vs body mass index and waist:height ratio (in mmol/L and mg/dL).  

While there is some scatter due to varying Personal Fat Thresholds, we can see there is a definite relationship between BMI and premeal trigger.  People with low BMI and waist:height ratios tend to have lower pre-meal triggers, down to 4.1 mmol/L or 75 mg/dL.  

As you delay your meals until your blood sugar reduces, you should also expect your weight and body fat to drop.  

24. Why does my blood sugar drop after I eat?

Some people find that their blood sugar drops after they eat.  This is not cause for concern, but rather a positive sign that you are metabolically healthy and/or you are not overeating carbohydrates.  

When you eat a higher protein meal, your pancreas secretes insulin to enable you to use the protein to repair your muscles and organs, make neurotransmitters and a host of other functions of amino acids.  Glucagon is also released by your pancreas to balance insulin as shown in this chart below (from Marks’ Basic Medical Biochemistry).  

For someone below their Personal Fat Threshold, this balance of insulin and glucagon means that their blood sugars will remain stable.  Blood sugars may even decrease, which is an indication that you have plenty of capacity to absorb the meal you just ate and the energy from your meal is not overflowing into your bloodstream.  

25. Why would my blood sugars rise after a low carb high protein meal?

Some people who are insulin resistant or have diabetes (i.e. insufficient insulin to maintain stable blood sugars) may see their blood sugars rise after a high protein meal as the glucagon kicks in to tell the liver to release stored glycogen.  Insulin is also released to keep blood sugars stable.  

However, if someone is insulin resistant, insulin does not work as effectively, and their blood sugars are not suppressed.  Therefore, people who are insulin-resistant may see a rise in blood sugars after a high protein meal because they have insufficient insulin to both metabolise the protein and suppress the release of glucagon from their liver at the same time.  

Some people see this rise in glucose and think they should avoid protein in an effort to maintain stable blood sugars.  However, this can just make things worse.  If you are insulin resistant (i.e. Type 2 diabetes) or your pancreas is not producing enough insulin (Type 1 Diabetes) you are likely losing protein through gluconeogenesis and would benefit by focusing on a higher protein percentage to ensure that you don’t end up having to overeat to get the protein your body needs.

If you are insulin resistant because you are carrying excess body fat, then the solution is to focus on foods with a higher protein percentage to increase satiety and enable you to lose body fat without losing excess lean mass.  

If you are already lean (i.e. waist:height ratio less than 0.5) and you are seeing elevated blood sugars after a low carb high protein meal then it may be useful to talk to your doctor to get your fasting insulin and/or c-peptide measured to understand if your pancreas is able to produce enough insulin to rule out Type 1 Diabetes or MODY.   

Rather than avoiding protein in an attempt to maintain flatline blood sugars, you should work to reduce the fat and carbs in your diet to enable your body to use up stored body fat while still providing adequate protein to preserve lean muscle mass.

See Why does my blood sugar rise after a high protein meal? for more detail. 

26. Don’t try too hard

Don’t try to push your blood sugar too far beyond your trigger point.  You want to feel a little hungry, not STARVING, before you eat.  Otherwise, you will be more likely to overeat at your next meal and delay the following meal even further.  

Data-Driven Fasting is a tool to ensure you are achieving an energy deficit over the long term.  Not surprisingly, it will be harder if you force a larger energy deficit.

Your mission is to find a sustainable rhythm of feasting and fasting while still moving towards your goal (e.g. weight loss, fat loss, lowered blood sugar or improved insulin resistance) over the coming weeks and months.

Hunger training helps you fine-tune your eating schedule and build long term habits.  If you push too hard, your body will find a way to overcompensate to avoid starvation.  Your goal is to find the minimum effective dose of fasting to move toward your goals in a sustainable manner. 

27. Quantified mindful eating

If you want to leverage the benefits of hunger training, you can make notes in the spreadsheet or keep a separate journal to record what you are learning and incorporate it into your routine in the future.

Unless you want to be testing your blood sugar before every meal for the rest of your life, it’s a good idea to build some new skills and habits to ensure this is sustainable for the long term.   

Before you eat, you want to be hungry, but not starving to the point that you trigger your binge instinct.  When you eat, you want to be full and satisfied, but not completely stuffed.   You may want to save the image below as your wallpaper on your PC or the lock screen of your phone as a reminder.

When you feel hungry and think of eating, rate your hunger.  Take a moment to imagine what your blood sugar might be if you tested it based on your physical symptoms of hunger (e.g. grumbling tummy, weakness, lightheadedness, etc.)?  Before long, you will start to get a pretty good feel for this as well as understand the factors that can influence your blood sugars (e.g. exercise, stress, hormonal changes, etc.).  

If you are hungry and your blood sugar is below your trigger, then go ahead and eat. There is no need to be a hero.  If you are hungry, but not too hungry, you are less likely to overeat and more likely to make better food choices.  

28. Plan what you will eat before you’re hungry

It’s critical to plan what you will eat before you get hungry.  If you test and decide to delay your meal, plan what you will eat for your next meal.  Plan to eat nutrient-dense foods with plenty of protein to maximise satiety so you won’t have to wait too long to eat again next time.   

Your goal when eating is to get adequate protein while keeping carbs low (to drain your blood glucose stores) as well as keeping fat low (to allow your body fat stores to be used).  When taken to the extreme, this approach is known as a Protein Sparing Modified Fast, but any diet that works over the long term tends to have adequate protein with less easily accessible energy from fat and/or carbs.  Because you are not fasting for days at a time, you will be less likely to feel like you should congratulate yourself with a pizza or a doughnut because you feel you “deserve it”.  

29. What should you eat after fasting?  

What you eat is just as important as when, how much or how often you eat.  If you fill up on energy-dense nutrient-poor food, your body will be craving nutrients again sooner.  So when you eat, do whatever you can to maximise nutrient density.  

You will be eating fewer calories when intermittent fasting, so you need to focus on getting more nutrients per calorie (i.e. nutrient density).  To help with this, we have developed a range of printable .pdf food lists to help you optimise your diet that you can access for free here.  If your blood sugars are still elevated, we recommend the blood sugar & fat loss food list.  If your blood sugars are relatively stable, then you can go straight for the fat loss food list.  

To help you optimise your feasting after you fast, we have also created a series of 22 recipe books optimised for a range of goals.  

The table below will help you find the right recipe book for you.  Click here or on the name of the book in the table to learn more about the recipe books or to purchase one. 

Approach Ideal for 
Low carb & blood sugarUse these if your blood sugars are consistently elevated (i.e. they rise more than 1.6 mmol/L or 30 mg/dL after meals).
Blood sugar and fat loss Ideal for anyone with elevated blood sugars and body fat to lose.
Fat loss Ideal for rapid fat loss with less hunger and cravings due to nutrient deficiencies and adequate protein to prevent muscle loss.
High protein:energy Use this if you want to attack your body fat without losing muscle, with maximum satiety.  

30. Should I track my weight when fasting? 

You don’t need to track your weight every day during Phase 2 – Hunger Training.  

Due to changes in water and food in your gut, your body weight can jump around from day to day.  While knowledge is power, some people find that tracking their weight AND blood sugar at the same time will be a struggle mentally.  

Some people love all the data, and it helps to keep them accountable. However, others find the data is too much effort to collect.  They may overthink the day to day fluctuations which can lead to burn out.   

While you can record your weight in the tracking spreadsheet every day, you only need to record your weight once per week to ensure you are making progress over time.

You should be pleasantly surprised that, especially in the first couple of weeks, you will lose weight quickly as your blood sugars decrease.  This may be mainly “water weight” (which is stored with the glucose in your liver and muscles).  However, once your glucose is depleted, your body will be able to access your stored body fat.  You need to go through this stage of losing water weight before you can start to burn through your body fat.

31. How often should I track my waist?

We also recommended that you track your waist circumference each week.  As shown in the chart below, a waist to height ratio of less than 0.5 is an excellent indicator that your metabolic health is approaching optimal.  Your waist measurement doesn’t change quickly, so you only need to measure it once per week.  

Your waist measurement is taken just about your belly button at the narrowest point of your abdomen in line with your elbows.  The precise location and whether you tend to suck in your gut to let it all hang out don’t matter too much.  Given our goal is to track long term progress, all that really matters is that you measure consistently.   

32. What are optimal body fat levels?

During Phase 2 – Hunger training, your pre-meal blood sugars will continue to decrease as you reduce your body fat levels to below your Personal Fat Threshold.  Using your blood sugar meter as a fuel gauge is an excellent indicator of whether you are carrying excess fat, regardless of your weight.  

A bodybuilder may have a high body mass index but still be healthy, so long as they are not carrying too much fat.  But even bodybuilders can gain too much fat in their pursuit of strength and will see their blood sugars start to rise.  Being strong doesn’t necessarily mean you have excellent body composition or excellent metabolic health.  

Data-Driven Fasting is a great way to ensure that someone looking to gain strength doesn’t gain excessive body fat that will compromise their metabolic health.   As you reduce your body fat levels into the fitness and athlete levels of body fat, you will find that your blood sugars also start to decrease towards optimal levels.  

Essential fat10-13%2-5%

The pictures below show what this looks like visually.    

As well as losing body fat, it’s also important to do whatever you can to gain lean mass (i.e. muscle) through exercise, particularly resistance training.  It’s your lean mass that is metabolically active and “burns calories”.  

People who lose excessive amounts of lean mass during fasting often find it extremely hard to sustain their weight loss because their metabolic rate has slowed so much.  They have to maintain a VERY low-calorie intake to avoid weight gain.  When you are extremely insulin sensitive, you can regain weight very quickly.  

As mentioned in this video from Dr Ted Naiman, morbid obesity and Type 2 is the other end of the spectrum to being a lean muscular bodybuilder.  While it’s not necessarily healthy to have extremely low levels of body fat (and very hard to sustain) many of us need to work to move in that direction a little more by losing body fat and gaining lean muscle mass.  

33. What are optimal blood sugar levels?

Generally accepted morning fasting and post-meal blood sugar ranges are shown in the table below.  

However, once your waking blood sugars are below 100 mg/dL or 5.6 mmol/L, you can be assured you are working within your Personal Fat Threshold and minimising your risk of all the diseases associated with energy toxicity and metabolic syndrome.  

If you feel you have more fat to lose and want to continue to work towards optimal, then continuing until your average fasting blood sugar is 80 – 90 mg/L (4.4 to 5.0 mmol/L) is a worthy quest.  

34. Does coffee “break my fast”?

Many people enjoy a coffee or tea in the morning and delay their main meal until later when they are hungry or their blood sugar drops below their trigger.  

This is fine, so long as you are not adding hundreds of calories worth of milk, butter, cream, sugar or MCT oil.  If you are tracking your fasting window (Phase 3), then you wouldn’t count your coffee or tea as your first meal.  

While there is plenty of debate over whether coffee or artificial sweeteners will break your fast and water only may be more optional, you need to find the balance between optimal and sustainable.  

In the context of Data-Driven Fasting where the goal is to fine-tune your eating to ensure a negative energy balance, non-caloric beverages like coffee aren’t going to be a problem, particularly if they enable you to compress your eating window in a sustainable manner.  

However, be aware that the calories from the cream, milk or sugar in your coffee will mean that it takes longer to deplete your stored energy, and therefore your blood sugars will take longer to drop below your trigger. 

35.  How much protein do I need?

Protein requirements will depend on your lean mass and your activity level.  

While 0.8 g/kg LBM is an absolute minimum to prevent deficiency, we tend to find people do better in terms of nutrient density and satiety with 1.8 g/kg LBM or ideally 2.2 g/kg LBM to prevent loss of muscle during weight loss. 

In percentage terms, we find people achieve better satiety and fat loss when they work up to 40% or more of their energy from protein.  Rather than eating more high protein foods, this is achieved by getting adequate protein and dialling back easily accessible energy from fat and carbs.  

A Protein Sparing Modified Fast is an extreme version of this and is considered by many to be the most effective way to lose weight without losing muscle.  But any weight loss diet that works over the long term tends to have less energy from refined fat and carbohydrate with more protein and fibre.  

You can use our simple macro calculator to see how much protein you need and track your intake in Cronometer for a few days to see what you are getting from your current diet.  

If you find you are not hungry, you don’t need to worry so much about the absolute protein intake (in grams) so long as your protein percentage is greater than 40%.  

36. Will fasting help my gut health?

While it can be hard to adjust to solid food after extended fasting for multiple days, many people find that shorter-term intermittent fasting improves their digestion and gut health.  

As we eat more than we need more often, our gut struggles to keep up and we get indigestion and overgrowth of particular bacteria.  As we eat less, we give our stomach a chance to rest and the excess ‘bad bacteria’ die off as they are not continually overfed with nutrient-poor inflammatory foods.  

37. How many meals per day should I eat?   

As you use your weight and blood sugar to monitor your progress, you should find that you quickly cut back on discretionary snacks.   

Our analysis of half a million days of food logging data found that people tend to eat fewer calories when they eat two meals per day.  We tend to choose more energy-dense foods when we’re REALLY hungry, so we tend to eat more with one meal a day than two meals a day.  It is also easier to meet your daily protein needs if you spread it across two meals rather than trying to get it all in at once.  

Many people who are older or less active find that one or two meals a day works well for them.  However, if you’re an active bodybuilder trying to build muscle, then more meals may be more helpful.

Not surprisingly, if we eat more often, we tend to eat more calories.  You don’t have to jump to two meals a day immediately, but eventually, you may settle on a manageable routine of two or three meals per day.  

If you find that two meals per day is still not working for you, you can decrease the size of those meals rather than skipping whole days of eating (unless you can ensure you can avoid eating highly energy-dense hyper-palatable foods after not eating for 36 hours). 

Data-Driven Fasting tends to work best when you use it to decide between one vs two or two vs three meals per day with a regular routine while focusing on food quality when you eat.

38.  How quickly will I lose weight with Data-Driven Fasting?  

As you can see from some of the examples of people who have used Data-Driven Fasting, the rate of weight loss can be quite rapid (up to 2.0% per week) if you can wait until your blood sugar drops below your trigger point most of the time.  

Greater compliance will lead to faster weight loss.  However, it’s critical to find a sustainable routine over the long term rather than pushing so hard that you find yourself overeating due to excessive hunger which will derail your long-term progress.  

Fasting and then refeeding on nutrient-poor low protein foods may be counterproductive and lead to weight gain and muscle loss.  Rather than pushing too hard, it’s much better to find a sustainable rhythm that allows you to maintain food quality when refeeding.

39. What is YOUR why?

Before you get too far into your Data-Driven Fasting journey, it’s important to reflect on your “why”.    

If you’re going to succeed at anything, you need to find the reason why you want to make a change.   Unless you have identified why you want to change, you probably won’t persist in taking the small incremental steps that will ensure long term success.  

Once you find Your Why, you can reflect on it and harness that motivation to keep you going through the hard times until you transform your hopes into habits!  Some example whys include:

  • I want to lose weight.
  • I want to be healthy so I can enjoy my life to the fullest.
  • I want to reverse my diabetes.
  • I want to gain control of my eating habits.
  • I want to avoid the health conditions of my parents and grandparents.
  • I want to like what I see in the mirror.
  • I want to think more clearly.
  • I want to reduce my body fat without losing muscle.
  • I want to have more energy.
  • I want to be more physically attractive.
  • I want to be healthy.
  • I want to set a positive example for my kids.
  • I want to respect myself more.
  • I want others to respect me more.
  • I want to avoid diabetes.
  • I want to be able to play with my grandkids.

40. What is your end goal?

It’s also valuable to think about where you would like to end up.  How long will you persist with Data-Driven Fasting?  What is your end goal?  

For example:

  • I want to maintain a weight below X kg/lb.
  • I want to maintain a body fat of less than X%.
  • I want to maintain a fasting blood sugar less than X mg/dL or Y mmol/L.

Setting a concrete end goal will ensure you continue with the process for the coming weeks and months until you reach it.   

41. How long can I do this for?  

You can follow Data-Driven Fasting until you achieve your goal glucose (i.e. waking of less than 90 mg/dL or 5.0 mmol/L) and body fat level (e.g. waist to height ratio of less than 0.5).  

Any form of dieting can get hard after weeks or months, so feel free to take a break and maintain your current weight for a while if life gets stressful.  You can always come back to it after a few days or weeks.

Once you reach your goal, we recommend you transition to Phase 5 – Maintenance in your Data-Driven Fasting tracking spreadsheet where you will track your weight, blood sugar and waist each weekend.  

If you find you are starting to gain weight or your waking blood sugar is increasing, you can simply jump back into your preferred Data-Driven Fasting protocol and repeat the process until you arrive at your goal again. 

42.  Will Data-Driven Fasting help me lose weight if I don’t have diabetes?

Phase 2 – Hunger Training will work for most people who are trying to lose weight, even if they don’t meet the criteria for diabetes.  

While Type 2 Diabetes is diagnosed when you have a fasting glucose of greater than 7.0 mmol/L or 125 mg/dL, you can use Data-Driven Fasting to drive your premeal trigger down to 4.5 mmol/L or 80 mg/dL.  

However, if you find that your blood sugars are so stable that you no longer get a useful signal from your pre-meal blood sugars, you can use one of the following approaches:

  • Phase 3.1 – Compress your eating window (fasting blood sugars) 
  • Phase 3.2 – Compress your eating window (weight) 
  • Phase 4.1 – Meal skipping (fasting blood sugars) 
  • Phase 4.2 – Meal skipping (weight)

43.  What to do if your waking blood sugars are not dropping

If you are achieving a negative energy balance, draining your excess glucose stores from your bloodstream and losing body fat, you should also see your waking blood glucose trending down over time.  

However, we can push our last meal back so late using hunger training that we end up overly hungry late at night.  It should not be surprising that your waking blood sugars are still elevated in the morning if you are still digesting the meal from the night before.  

We understand that many people find it easier to eat later in the day.  You will need to work to personalise your fasting approach to suit your lifestyle and preferences.  However, you should be aware that you are typically less insulin sensitive later in the day, and your blood sugars will tend to rise more.  

Plenty of studies (such as this one) show that people who eat more later in the day tend to have worse metabolic outcomes.  So, while it’s useful to make sure you wait until your blood sugars decrease to below baseline before eating, the best way to manage this may be to finish eating earlier or even prioritising a high protein meal earlier in the day that you eat regardless of your blood sugars.  You can then treat your other meals as discretionary based on your blood sugar.  

We’ve added a reminder in the spreadsheet to flag if your blood sugars are rising to help you focus on finishing eating earlier rather than just waiting until later to eat.  

Another factor to consider is your protein percentage.  People who have body fat to lose but eat a lower protein percentage may see a minimal variation in their blood sugar during the day after meals.  However, their body is still able to release plenty of stored energy into their bloodstream overnight, which means their blood sugar is elevated in the morning.  Prioritising a higher protein percentage (i.e. by reducing dietary fat and carbs) will provide greater satiety which will help with fat loss, and, in time, a reduction in waking blood glucose.  

44.  What is Dawn Phenomenon? 

Your body clock (i.e. circadian rhythm) is closely tied to your eating, sleeping, activity and light exposure.  

As your body prepares to wake in the morning melatonin decreases and cortisol and adrenaline start to rise.  Your body releases more glucagon to dump glucose into your bloodstream to ensure you are fueled and ready to bounce out of bed to start the day.  

This increase in glucose (stimulated by glucagon) is usually balanced by insulin which ensures your blood sugar is regulated and doesn’t rise too much.  However, people with diabetes or insulin resistance often find that their blood sugar increases a lot first thing in the morning due to what is known as the Dawn Phenomenon because the glucose release is not balanced by adequate insulin.  

There is no need to eat immediately if your blood sugars are high, especially if you are not hungry.  As you draw down on your excess fuel, you will start to see your waking blood glucose levels reduce.  However, if you are finding that your waking blood sugar is not decreasing because you are waiting too long before your blood sugars drop below your trigger, it may be wise to have a higher protein meal earlier in the day when you start to feel hungry, even if your blood sugars are above your current trigger.  

The small amount of insulin from the protein-rich meal may help stabilise your blood sugars for the rest of the day as well as leave you less hungry later in the day and prone to a late-night binge that will cause your blood sugars to be higher in the morning.  

45. What is the best way to measure body fat?  

Tracking your body fat percentage is useful to ensure you are losing fat rather than precious lean muscle mass which is highly metabolically active.  The last thing you want to do is lose muscle and end up looking like a fat skeleton with a very low metabolic rate and have to maintain an extremely low-calorie intake to keep the weight off! 

There are many ways to measure body fat.  None of them are perfect.  

  • A DEXA scan is the most accurate but expensive and inconvenient, so most people are unlikely to do it regularly.  
  • The Navy Fat calculator is surprisingly accurate (i.e. aligns with DEXA scans) and is based on a simple measurement of your waist, hip and neck as well as your weight.  
  • The most convenient tends to be bioimpedance which can be measured with most modern scales.  These may not be as accurate as DEXA, but they can give you a consistent trend to tell you if you are heading in the right direction over the long term (as shown in the example below from one of our 6 Week Nutritional Optimisation Masterclass participants).  

Bioimpedance scales count your water weight “lean mass” and hence it can bounce around from day to day and will also decrease initially as your blood sugars decrease and you lose ‘water weight’.   But over time, you should see a nice downward trend.

If you look leaner and healthier, you probably are.  In the Nutritional Optimisation Masterclass, we use your body fat and lean mass measurements to dial in your protein intake.  However, body fat measurements are not critical for Data-Driven Fasting.  Your waist measurement and selfies will do the job just fine if you don’t have a bioimpedance scale.   

46.  Electrolytes and fasting 

Electrolytes (i.e. sodium, potassium, magnesium, etc.) are critical, especially when you are losing weight.  

One of the many functions of insulin is to help your kidneys recycle electrolytes in your body.  When insulin levels decrease, you will lose excess water as well as more electrolytes.  You may feel light-headed or experience muscle cramps if you do not have adequate electrolytes on board.  Much of what we experience as “hunger” is actually a craving for minerals.  

While many people find adding mineral salt to their water, drinking bone broth or even pickle juice is helpful, it’s also critical to ensure you are getting all the essential minerals, not just sodium.   We have created an Optimised Electrolyte Mix with the optimal amounts and ratios of sodium, potassium and magnesium that you can try.  

However, the problem with mineral salts is that you can quickly reach your ‘gut tolerance’ so you still may not be able to get the amount you need from supplements.  As always, it’s best to get your nutrients (including minerals) from food first and supplement only if necessary.  

To find out whether you need more minerals in your typical diet (and which foods and meals you need more of), you can track your usual food intake using our Free 7 Day Food Discovery Challenge

47.  How can I optimise my sleep with intermittent fasting?

Not eating too late in the day also seems to help us sleep better.  According to Professor Matthew Walker in his book Why We Sleep, we don’t enter into REM sleep while we are burning off a lot of energy from dinner.  This survey of Oura Ring users shows that not eating too late is by far the most beneficial “hack” to ensure good sleep based on their quantitative data.  

Don’t be surprised if you find you sleep more soundly as your blood sugars start to decrease because your body is not working so hard to process excess energy overnight.  But at the same time, it’s good not to be too hungry when you go to bed.  

48.  Do I have to check my blood sugars before every meal?

No.  You don’t have to check your blood sugar before every meal of the day.  It may be better if you find one Main Meal that you know you eat well at a regular time each day (e.g. dinner with your family or your protein-packed breakfast) and use your blood sugar to decide whether you eat at other times through the day.  

49. Eat “breakfast” like a king 

While you don’t have to have “breakfast” first thing in the morning, it appears to be ideal, if possible, to front-load your calories towards your first meal of the day rather than eating your biggest meal right before you go to bed.   This is known as early time-restricted feeding (eTRF).  

Not only are you more insulin sensitive earlier in the day, but you are also more likely to use the food you just ate to fuel your activity rather than storing it while you sleep.  If your schedule allows it, you should try to eat most of your food when the sun is up to synchronise your circadian rhythm with your eating patterns.  

If you are finding you are overeating at night and your waking blood sugars are not coming down, it might be worth trying to lock in a daily high protein meal earlier in the day (even if your blood sugars are still above your trigger point) so you are less hungry at night. 

50.  How much should my blood sugars rise after a meal?  

Data-Driven Fasting focuses on your blood sugar before meals to ensure you are reducing your body fat.  As your insulin sensitivity improves your waking blood sugars and post-meal blood sugars should also start to fall.  

Be careful not to try to achieve flatline blood sugars by avoiding protein and all carbs (especially non-starchy vegetables which can be nutritious and satiating).  However, if you see your blood sugar rise by more than 1.6 mmol/L or 30 mg/dL at one hour after a meal, it means that you likely ate too much or too many carbohydrates at that meal.  

Many people find that their blood sugars rise more after dinner, which is an indication that they should reduce the size of their dinner and prioritise larger meals earlier in the day.  

So long as your blood glucose is staying within the ‘normal range’ (as shown below) a larger rise in glucose after you eat is more a reflection of what you ate (i.e. too much fast-acting carbs), while your fasting blood sugars and your glucose before meals is an indication of your metabolic health and whether you are over-fueling across the day.  

During the baselining period, you will get an idea of how your blood sugars respond to your current diet and whether you need to reduce your current carbohydrate intake.  However, most people won’t need to be too concerned about their post-meal blood sugar if they are focusing on nutrient-dense whole foods which typically don’t contain refined grains or added sugars.  

51.  Can I edit my spreadsheet on my phone?

The Data-Driven Fasting spreadsheet works best on a PC browser.  You can access it from anywhere using the link that you will receive.  

Rather than saving a local copy, we would prefer that you use the provided link to enter your data.  This will allow us to troubleshoot your spreadsheet and make refinements to the system.  

However, if you use OneDrive and the Excel app on your phone, we can send you a share link so it will appear in your OneDrive files on your phone to make it more convenient.  

If you use Google Drive, we can also send you a link to Google Sheets that will work with the app on your phone or iPad rather than Excel.  

52.  How is Data-Driven Fasting different from calorie counting?

Managing calories in vs calories out sounds simple, but it is incredibly difficult to implement over the long term.  Tracking is inaccurate, our energy needs change over time, and our lizard brain often finds a way to trick us into eating more.  Our lizard brain appetite also doesn’t like to be controlled by an external force for too long, and psychological disorders can develop.  

Data-Driven Fasting respects the law of conservation of energy but uses your blood sugar or your body weight as a fuel gauge to guide your meal timing to ensure that you are in a negative energy balance and moving towards your goals.  

53.  How is Data-Driven Fasting different from other fasting techniques?

Most approaches to fasting use multi-day fasting in the hope of reducing insulin and causing autophagy.  By contrast, Data-Driven Fasting focuses on the long term trend by managing shorter bursts of restriction to ensure your blood sugars and weight are moving in the right direction.  

Just like any smart fitness training routine balances exercise and recovery to ensure positive adaptations, Data-Driven Fasting ensures that your short periods of energy deficit are balanced with nutrient-dense feeding to ensure long term progress.

By doing this, we ensure that diet quality is maximised (i.e. adequate protein and nutrients) during feeding rather than the energy-dense bingeing that often follows multi-day fasts.  By achieving a balance of adequate duration of fasting and quality feeding at a micro level, we optimise the long term trend to move towards our goals.  

54.  Will “too much protein” raise my insulin levels and stop me losing fat?  

Refined carbohydrates raise insulin a lot over the short term, protein raises insulin less but over the medium term, while fat raises insulin over the longer term.  While we typically focus on the change in insulin levels due to our food, our overall insulin production across the day is more closely related to our total calorie intake and our body fat levels.  See Making sense of the Food Insulin Index for more details.

We require insulin to keep our body fat in storage while we eat.  Someone with Type 1 Diabetes will essentially disintegrate, with all their stored energy flowing into their bloodstream, if they do not inject adequate insulin.  However, for someone who has a functioning pancreas, insulin production will be proportional to their body fat levels and how much energy they need to keep in storage.  

While protein does elicit a short term insulin response, it is the most satiating macronutrient.  Prioritising adequate protein when we eat allows us to eat less over the long term, reduce body fat levels and reduce our basal insulin levels and requires less insulin across the day.  

55.  Do I need to worry about insulin?  

While many people focus on insulin as the “root problem” and lowering insulin as the end goal, the reality is that your body won’t produce more insulin than you need to keep your body fat in storage while food is coming in from your mouth.  

If you inject excess insulin, your liver will reduce the release of energy into your bloodstream, and your blood sugars will drop.  You will feel ravenously hungry and will eat anything and everything until your blood sugars rise again.  

Unless you are injecting insulin (i.e. type 1 or insulin-dependent type 2 diabetes), high insulin levels do not cause overeating or obesity.  The reverse is true.  High insulin levels are caused by overeating and obesity.  Rather than worrying about ‘insulin toxicity’, should focus on managing energy toxicity and insulin will look after itself.  

The Carbohydrate – Insulin Hypothesis simplistically assumes:

carbs -> insulin ->  fat storage 

But in reality, it is a little bit more complex. It’s critical to understand the true cause and effect relationship, so we are not trying to the symptom.  A rise in insulin is a response to increased body fat (not the cause):

low satiety nutrient-poor foods -> increased cravings and appetite -> increased energy intake -> fat storage -> increased insulin

Hence, the solution to managing your diabetes, blood sugar, insulin levels and avoiding the complications of metabolic syndrome is:

high satiety nutrient-dense foods and meals -> decreased cravings and appetite -> decreased energy intake -> fat loss -> lower insulin levels

By managing blood sugar, you will reduce your body fat which will, in turn, reduce your insulin levels.  Merely focusing on maintaining flatline blood sugar and insulin levels can lead us to consume energy-dense high fat low satiety foods that lead to weight gain and increasing insulin resistance over the long term.  

56.  Will I be getting enough autophagy with Data-Driven Fasting?  

While there is a lot of talk about autophagy (i.e. self-eating) when we don’t eat, there is little understanding of the actual length of fasting required to achieve an optimal amount of autophagy.  

Too much autophagy can be harmful if you are losing precious lean muscle mass when you fast and don’t get enough protein when you eat.  Data-driven fasting ensures you get regular small episodes of autophagy as your critical markers (i.e. body fat, blood sugars, insulin, etc.) move towards optimal.  

These cumulative smaller bursts of autophagy followed by nutrient dense refeeding are much more likely to be beneficial than a few multi-day fasts followed by energy-dense nutrient-poor binging.  

57.  How is Data-Driven Fasting different from the Fast Mimicking Diet?  

The Fast Mimicking Diet attempts to provide a small amount of nutrients and reduced protein during a multi-day fast.  Developed by Valter Longo, the FMD stems from a plant-based belief system where animal protein is bad.  

Data-Driven Fasting is more like a Protein Sparing Modified Fast, which prioritises adequate protein and more nutrients per calorie during the limited feeding opportunities.  By maximising nutrient density, you will ensure that your body still gets what it needs during weight loss to optimise mitochondrial function, prevent loss of metabolically active lean muscle mass and minimise cravings to maximise your chance of long-term success.  

58.  Do you need MCT oil or butter during a fast (aka “Fat Fasting”)?

Adding refined oils or fats will be counterproductive if your goal is fat loss, insulin sensitivity, improved body composition, nutrient density or diabetes reversal.  

59.  Should I exercise?

Resistance training is critical to send a signal to tell your body that you need to maintain your muscle during weight loss.  But be aware that your blood sugars may go up or down due to exercise, so you should only use your blood glucose as an indicator of when you should eat after your blood glucose has settled down (i.e. an hour or two after exercise).  

If you feel hungry around your workout, you can choose to eat one meal in the morning just before or after your workout (regardless of blood sugars).  Ideally, this should be protein-rich to support recovery.  You can then treat the other meals and snacks across the day as discretionary and only eat if your blood glucose is below your trigger.  

60.  Can I fast when I’m stressed?

The extra adrenaline and cortisol from stress can cause your blood glucose to rise, regardless of what you eat (or don’t eat).  Stress can also cause your lizard brain to become insecure, so you will comfort eat to prepare for an emergency (e.g. famine or to run away from a predator).  

As well as waiting to eat, you can lower your blood glucose by doing whatever works for you to relax and de-stress (e.g. breathing exercises, meditation, a walk in the sun, sleep in, relaxation, etc.).  Don’t be surprised if actively managing your stress also helps you to lose weight.  

61.  How should you break a fast?

Many people find they experience gut distress and diarrhoea when they eat again after fasting for days at a time and have to eat special foods to acclimatise their digestive system to eating again.  However, this is not the intent of Data-Driven Fasting.  We want to optimise your day to day eating routine so you can consume good food to satiety without digestive issues or bingeing.  

62.  What is an “extended fast”?  How long is too long?

While you can go for weeks without food, it may not be optimal.  However, for the many people who eat all day, a couple of hours may feel “extended”.  

While Data-Driven Fasting is designed to enable you to dial in your daily eating routine (most people land on a regular eating schedule of three/two or two/one meals per day) there is nothing wrong with going 24 or 36 hours without food so long as you are making good choices when you refeed to ensure you are getting the nutrients you need over the longer term.  

If you find yourself reaching for the peanut butter, nuts, cream, pizza etc. after fasting, chances are you’ll do better if you are a little less ambitious with your fasting duration next time.

63.  Would Data-Driven Fasting be appropriate if I’m active or a bodybuilder?  

Yes.  One of the challenges for active people is getting enough fuel to recover and grow without eating so much that they add excess body fat.  Hunger and energy requirements can vary radically from day to day based on the amount and type of activity you do.  Your blood sugars give you an instantaneous fuel gauge to tell you if you need to refuel.  

It’s valuable to refuel if your blood sugars are low so you don’t get too hungry and will be more susceptible to binge later on.  However, given that your blood sugars are closely tied to body fat levels, using your blood glucose as a fuel gauge also enables you to kerb your appetite rather than feeling entitled to eat unlimited amounts of energy that will leave you gaining fat despite all your hard work.

64.  Can you drink alcohol while fasting?

Alcohol tends to decrease your blood sugars.  Alcoholics often have low HbA1cs.

However, this is not necessarily a good thing.  

  • Due to oxidative priority, your body has to burn off the alcohol before your glucose and fat, so you will downregulate the release of glucose (and fat) into your bloodstream until your body clears the alcohol that it cannot store.   
  • We tend to make poorer food choices after a significant amount of alcohol that will keep your blood sugars elevated for longer.  
  • At seven calories per gram, alcohol is energy-dense (compared to fat which is nine calories per gram and carbs and protein which contain four calories per gram).  
  • Alcohol often comes with plenty of carbs and other yummy things that are easy to overdo.  
  • While alcohol knocks you out and some people think they fall asleep faster, you don’t get into REM sleep as quickly because your metabolic rate is elevated while you burn off all the high-octane energy from the alcohol.  So, not only will you feel dehydrated and have a hangover, you won’t have slept as well either.  
  • Alcohol is effectively empty calories’ (i.e. similar to sugar, refined grains or oils).  It contains lots of energy with very few nutrients, so it won’t help you on your quest to maximise nutrient density.  

65.  Will I lose weight more easily if I’m insulin sensitive?  

There is a common misconception that being insulin resistant or having type 2 diabetes makes it harder to lose weight.  However, the opposite is true.  We become insulin resistant because we are obese, not obese because we are insulin resistant.   This distinction is important.  

People who can gain a massive amount of weight are often highly insulin-sensitive, with normal blood sugars, even with much higher levels of body fat before they develop diabetes.  

People who are lean are typically much more “insulin sensitive”, meaning that they can quickly gain weight (both muscle and fat) when they eat.  Weight loss generally slows as someone becomes leaner, and hunger increases to prevent starvation.  

It takes a massive amount of discipline and self-restraint for bodybuilders to diet down for a bodybuilding show, and many of them regain it extremely quickly afterwards due to their uncontrollable appetite.

As a general rule, someone who is obese is more likely to be insulin resistant and have elevated blood sugars, with excess energy overflowing into their bloodstream.  It’s hard for them to gain more body fat because their adipose tissue is already full.  

Once they drain the excess energy from their bloodstream, they will be able to lose body fat.  Their pancreas is likely struggling to continue to produce enough insulin to keep all excess energy in storage.  As they lose body fat, their insulin levels will reduce, and they will become more sensitive to the effects of insulin.  

66.  Could extended fasting harm your metabolism and make you fat?  

Your body LOVES routine.  

While daily intermittent fasting can be useful to compress your eating window to give your metabolism and digestion time to rest, repair and use up your glucose and fat stores without constantly being topped up, there is a risk that your lizard brain will get confused if you subject it to extended periods of fasting or irregular meal timings.

If you go out and eat a big meal late on Friday night, sleep on Saturday and Sunday and eat then go back to work on Monday with an early breakfast your body gets metabolic jet lag.  Your circadian rhythm is tied to not only the sun and light signals but also your activity and eating patterns.  

As a general rule, it is ideal to eat the majority of your calories when the sun is up, and if possible, earlier in the day when you are more insulin sensitive, and your body is primed to use the energy rather than store it.  But regardless of whether you practice early time-restricted feeding (eTRF) or one meal a day (OMAD) at dinner, your body prefers a regular eating schedule.  

Similarly, your body can become confused when you skip eating for days at a time and then eat to satiety on other days.  As you push through hunger on some days, you tell your lizard brain that food is scarce, so next time you eat, you will likely eat more than you need to to ensure that you have enough food for the next self-inflicted famine.  

Hence, we strongly recommend you develop a regular eating routine that is fine-tuned by your blood sugar and weight data to tell you whether you need more or fewer meals.  

67.  Is my thyroid stopping me from losing weight?   

Many people who are over fat and have metabolic syndrome have some level of thyroid dysfunction.  However, similar to insulin, this is often a result of obesity rather than the cause of obesity.  

If you are taking medication for your thyroid, you should continue to have your thyroid-stimulating hormone (TSH) monitored by your health care team and adjust your medications as required.  

Your thyroid is a central governor for your metabolism.  Similar to insulin and pancreatic burnout, your pituitary gland will ramp up its production of thyroid-stimulating hormone to rev up your metabolic rate if you have more energy to burn off.  As you lose weight and reduce your blood sugars, your body won’t need as much thyroid-stimulating hormone to keep your metabolism elevated, and your levels may decrease.  

It’s also worth noting that nutrient density is critical to healthy thyroid function (particularly selenium, iodine, niacin, histidine and tyrosine), so prioritising whole-food nutrient-dense meals is also a crucial part of the equation.  

68.  Fasting is stressful 

A little bit of stress can be beneficial (i.e. hormesis or eustress).  Our body likes consistency and routine, but complete stagnation and monotony lead to weakness and atrophy.  

The seasons (e.g. autumn, winter, spring and summer) naturally forced our body to go through cycles of different food availability and bulking and cutting.  Any good workout routine involves periods of progressive overload interspersed with rest and recovery.  

However, too much stress beyond the point that we can quickly adapt and recover (i.e. distress) is not good and forces our body to take evasive action.  Data-Driven Fasting ensures that our eating routine is punctuated by just enough stress to keep our body moving forward towards our goals.  As we incrementally lower blood sugar, weight, fat, insulin resistance,  improved metabolic health will follow.  

69.  Should I fast when I’m sick?

Infection and inflammation can affect your blood sugar.  You may need more food for recovery, or you may lose your appetite while your body takes some downtime to heal when you are unwell.  

When you’re sick, you can take a break from testing your blood sugars and follow your regular eating routine or just listen to your healthy appetite signals and eat when hungry.  You can re-commence Data-Driven Fasting once you recover.  

70.  How to “build your fasting muscle”

Lots of people talk about “building their fasting muscle” as if they just need to do it longer and harder to get more benefit.  Sadly, when it comes to fasting or exercise, the majority of people go too hard too early and burn themselves out before they experience the real benefits or develop a sustainable routine that will provide significant benefits over the long term.

You need to make sure you are doing the right exercise, not overdoing it, getting adequate recovery and getting the minimum effective dose by measuring your progress.  Data-Driven Fasting provides a systematised approach to ensure you are covering off on all these critical elements to ensure long term sustainable success.  

  • By measuring your waking and after-meal blood sugars, you can make sure you are doing the right exercise (i.e. finding the right balance between delaying your first meal and finishing eating earlier).
  • By prioritising high satiety nutrient-dense food, you maximize your recovery from fasting, ready to go ahead sooner.
  • By waiting to eat when your glucose is below your trigger point ensures you are getting the minimum effective dose without overdoing it.
  • By tracking your blood sugars, weight and waist, you will ensure you are making progress and being rewarded for your effort as you progressively lower your premeal trigger.

71.  Do I need to track before every meal or every day?

No.  You don’t need to log every meal for Data-Driven Fasting to work.  However, when you start out, you will get the maximal benefit from measuring more often to guide your routine.  After a while, you will build new habits and get a better appreciation for your real hunger.  

You may lock in your main meal and only test before discretionary meals.  If you are on holidays or can’t test for a few days, you can pick up where you left off without feeling like a failure.  You will quickly find if you have overfilled your fuel tanks while you weren’t tracking.  

72.  How long will it take to train my hunger? 

People with elevated blood sugars tend to have more dysregulated hunger signals and find it harder to judge their true hunger, hence monitoring blood sugars is a great way to train your hunger if you are overweight or have elevated blood sugars.  

A number of fascinating studies (e.g. Training to estimate blood glucose and to form associations with initial hunger) have shown that people can learn to predict their blood sugars and hunger from their feeling of hunger over a number of weeks.  

After several weeks of testing blood sugars, people can get a good feel for their blood sugars when they are actually hungry based on their symptoms (e.g. gastric symptoms, abdominal sensations or mental fatigue).  

Once you can predict your blood sugar and rate your hunger based on your symptoms and wait until you are actually hungry to eat you will be ready to wean yourself off the measuring and rely on your hunger signals to understand if you need to eat.  

73. What if my blood sugars rise again before I eat?  

The goal of hunger training is to verify that your hunger is real based on your blood sugars.  

If your blood sugars are below Your Personalised Trigger when you feel hungry, then it means you have successfully depleted the glycogen in your liver and have started to burn fat.   You have validated your hunger as real, you have used up the energy in your system from your last meal and are ready to refuel again.  

Some people have noticed that when they test again before they eat that their blood sugars may have risen while they prepare their meal.  It is perfectly normal for your body to release glucose into your bloodstream:

  • when it anticipates food is coming, 
  • as part of the normal process of maintaining stable blood sugars, or 
  • if it gets stressed by low blood sugars and hunger.  

The “secret” here is not to test again.  Just go ahead and eat if you are hungry and your blood sugar has dipped below your trigger.  This is one of the downsides to using a continuous glucose monitor for hunger training as it can provide more data than necessary.  The goal is to leverage the minimum effective dose of measurement to ensure you are moving progress rather than becoming overwhelmed by data.  

74.  Can I reset my trigger?

Keep in mind that your “current trigger” will progressively ratchet down (not up).  If you have a blowout weekend or a party, you will likely need to fast longer or more often to catch up and reach your trigger point.  Before long, you will learn to think twice before overfilling your fuel tank again.  

If you backslide for a couple of weeks and you find you can’t catch up to your trigger without excessive hunger that leads to bingeing, you can overwrite your calculated trigger value with a slightly higher trigger value.  Still, consistency is the secret to long-term success.  Ideally, there won’t be too many times that you have to reset your trigger.  

75.  Should I eat less protein if I have diabetes?

Some people mistakenly try to achieve perfectly flatline blood sugars by reducing both their protein and carbohydrates to very low levels.  Unfortunately, this often ends in overeating low satiety nutrient-poor high-fat foods which in turn leads to increased energy intake, weight gain and insulin resistance!   

If you are insulin resistant or have elevated blood sugars, there will be a greater protein from your diet “lost” in the conversion to glucose via gluconeogenesis and hence not available for muscle protein synthesis.   To make up for the protein that has been lost in the conversion to glucose, your appetite will increase, and you will consume extra energy to get the protein you need.  

Hence, it is crucial for people with Type 2 Diabetes or any degree of insulin resistance to emphasise a higher protein percentage (by reducing easily accessible energy from carbohydrates and fat) until they can optimise their body composition and become more insulin sensitive.  

76.  Spreadsheet housekeeping 

Once you work out which meals you eat regularly, there may be some blank space in your spreadsheet. To hide the columns you’re not using, simply right click on the column label at the top of the sheet (e.g. on the M for the ‘before evening snack’ column) and click on ‘hide’. This will help to make your spreadsheet a little tidier for day to day use.  It will also help you solidify your identity that you are not someone who snacks after dinner.  

77.  Which protocol is right for you?

The table below summarises the different Data-Driven Fasting approaches.  We recommend you start with Phase 1 and then progress to phase 2, but you can jump straight into phase 3 or 4 if you are not eager to test your blood sugar.  

Phase GoalMeasurement 
1. BaseliningFind your pre-meal blood sugar trigger Blood sugar on waking, before and after meals.  Weight, waist and body fat (also recommended).  
2. Hunger trainingEliminate snacks and extend the time between meals to force a long term negative energy balance.  Finish eating earlier if waking BGs are elevated.  Test blood sugars when hungry.Record waist, waking glucose, body fat weekly.
3.1  Eating window (with blood glucose)  Compress your eating window to reduce waking blood glucose.Waking glucose and time of first and meal/calories (daily).Track weight, waist and body fat (at least weekly).
3.2  Eating window (weight)Compress your eating window based on your weightBodyweight and time of first and last meal (daily).Track weight, waist and body fat (at least weekly).
4.1 Meal  skipping (blood glucose)Reduce your number of meals based on your waking glucose.Waking glucose (daily).Track weight, waist and body fat (at least weekly).
4.2  Meal skipping (weight)Reduce your number of meals based on your weight.Weight glucose (daily).Track weight, waist and body fat (at least weekly).
5  Maintenance Maintain your progress over the long term! Weight, body fat and waking glucose weekly.

78.  When should I progress to the other phases of Data-Driven Fasting?  

The table below will give you some guidance as to when you should consider moving on from Phase 2 – Hunger Training.  

Waking blood sugars are high but daytime sugars are low and stable.Many people on a high fat keto diet find that they have very stable blood sugars during the day although they have elevated blood sugars and plenty of weight to lose.  If this is the case for you, try dialling back added fats and prioritising foods with a higher protein percentage to increase satiety before moving on from Phase 2 – Hunger training.
I don’t like testing my blood sugars during the day.Try phase 3.1 or phase 4.1 (which only requires you to measure your waking blood sugars).
I hate tracking blood sugars!Try Phase 3.2 or 4.2 which only require you to track your weight each day.
My waking blood sugars are great and my trigger value is no longer dropping but I still have weight to lose.Congratulations on reversing your insulin resistance and diabetes!  Try Phase 3.2 or 4.2 until you reach your goal weight.  
I have reached my target blood sugars, body fat and weight.Congratulations!  Move onto Phase 5.  Maintenance.  

79.  Is there a certain blood sugar that indicates I am “in fat-burning mode”?   

You are always burning some combination of fat and glucose.  When you’re active, you burn more glucose and more fat at rest.  

If you have a lot of glucose in your system, your body has to burn through the glucose first (due to oxidative priority), so you won’t be burning as much fat.  As you wait until your glucose is dropping below your personalised trigger before you eat, you will ensure that you are burning more fat at the end of each fasting period.  As you progressively lower your trigger, you will be burning more fat and less glucose.  

As your premeal blood glucose levels reduce, your body will progressively turn to burn more fat, particularly at rest.  As your fasting glucose trends towards more optimal levels (i.e. 90 mg/dL or 5.0 mmol/L) then you will be burning more fat.  So long as you are nut supplying excess dietary fat, you will be burning body fat when your glucose levels are low.

80.  But my fingers hurt!  

While people tend to prick their fingertips to test blood sugars, they are also one of the most sensitive parts of your body.  While blood sugar will vary a little depending on where you take them, you can take your blood sugar anywhere (e.g. the outside of your forearms where you are less sensitive).  Just be consistent.  

81.  If my blood sugar is below my trigger when I wake should I eat?

If you are above your Personal Fat Threshold, you will likely see more elevated blood sugars in the morning.  However, some people find that their blood sugars are below their trigger when they wake and wonder if they should eat. 

The answer here is no.  The goal of Data-Driven Fasting is to eat when you are hungry and require fuel, not just when your blood sugars are low.  You would ideally wait until later in the day when you are hungry, and your blood sugar is below your trigger.  However, if your blood sugar tends to rise through the day, locking in a protein-focused meal earlier in the day as your main meal and then using your premeal trigger for other discretionary meals may also work well.   

82.  How do I get my Data-Driven Fasting Spreadsheet?  

We’re eager for people to find their baseline trigger, so we set up a simple baselining spreadsheet that you can get for free here.  

However, after sending out more than 400 free spreadsheets to people who were eager to trial Data-Driven Fasting, we found that people needed a structured program to guide them through the process and pitfalls.   

So we created the Data-Driven Fasting 30-day Challenge to guide people through the process in a structured and systemised manner.  The full spreadsheet is now part of the package of materials you will get when you sign up here.  

Join us for the Data-Driven Fasting 30-Day Challenge

The Data-Driven Fasting 30 Day-Challenge will guide you through the process of optimising your fasting routine, including:

  • Baselining – Identify Your Current Trigger that you can use to identify true hunger and when you need to eat to refuel.
  • Your current foods/meals – Learn how the foods you currently eat affect your blood sugar; which ones leave you satisfied and which ones lead you to eat more than your need.
  • Hunger training – Learn to delay eating until your blood sugar is below your trigger to make sure that you eat only when you need to refuel, to ensure that you are lowering your blood sugars and burning body fat.
  • Curb your late-night binging – Use your waking blood sugars to identify if you are eating too late.
  • Main Meal vs Discretionary Meals – Identify the Main Meal that you will use to anchor your eating routine and ensure you get enough nutrients. You can then treat the others as Discretionary Meals to meet your energy needs as required, based on Your Current Trigger.
  • Optimise your eating routine – Lock in your new eating routine which will guarantee you are moving towards your goals.

What you will get:

  • 30-day program to guide you to optimise YOUR fasting routine to ensure you achieve your goals.
  • A Data-Driven Fasting Tracking Spreadsheet to track your progress and optimise your intermittent fasting routine.
  • A 131-page manual complete with detailed instructions and answers to frequently asked questions.
  • A workbook that you can use to reflect on your learning during the challenge
  • ​Private Community with daily posts, support.  

Join here to get access to your spreadsheet and materials to make sure you’re ready for the next Data-Driven Fasting 30 Day Challenge

Marty Kendall