What makes Data-Driven Fasting Different?

Since we started the Data-Driven Fasting Facebook Group in May 2020 and throughout the Data-Driven Fasting 30-Day Challenges, we have received a LOT of questions from people trying to make sense of their blood glucose. 

As people hesitantly began learning the hows and whys of using their blood glucose to guide when and what to eat, we fielded the same questions so often that we developed an extensive array of Frequently Asked Questions (FAQs).   

The essence of Data-Driven Fasting is simple and works best when you don’t overthink and second-guess it.  All you need to do is follow the guidance from your blood sugar meter.

But tracking their blood glucose tends to make people curious and full of questions. As a result, we’ve worked hard to answer them to provide a deeper understanding to empower you to comprehend your fascinating metabolism and tweak the process once you have mastered the basics.  

Feel free to use this manual as a searchable reference as you chase your trigger in the Data-Driven Fasting 30-Day Challenge

Once you understand the various things that can affect your blood sugars, you’ll be able to ‘hear’ the signal from your blood glucose and ignore all the noise.  While the details may appear complex, our ultimate end goal is simplicity.  

Once you become acquainted with your true hunger signals and make peace with your survival instincts, you will no longer need to rely on your blood sugar meter as a crutch.

But be patient!  It’s allowed to take some time.  You will reach your goal faster if you follow the process and don’t stress or try too hard.  

Rather than trying to control your blood glucose levels and getting frustrated when they don’t behave, we encourage you to approach the process as a curious student and use the information from your blood glucose meter to guide your progress. 

Most approaches to fasting encourage you not to eat for days at a time in the hope of reducing insulin and driving autophagy.

In contrast, Data-Driven Fasting focuses on the long-term trend with shorter bursts of restriction driven by personal intuition to ensure your blood glucose and weight are moving in the right direction. 

Like any intelligent fitness training routine that balances exercise and recovery to ensure beneficial adaptations, Data-Driven Fasting ensures that short periods of energy deficit are balanced with nutrient-dense, high-satiety meals to achieve long-term progress. 

If you go all out in the gym and push yourself much harder than your body is used to, you’ll be sore and tired for days.  So, you’ll be less likely to come back the next day to work out.  This will slow your long-term progress.

Similarly, it will be easier to maintain your diet quality if you don’t push to the point that you are ravenously hungry and your blood glucose is way below your current trigger.  By balancing bouts of fasting and nutrient-dense feeding, we optimise the long-term trend to move towards our goals. 

Rather than adopting an arbitrary eating window that may (or may not) work for someone else, Data-Driven Fasting enables you to fine-tune your routine to your unique metabolism, schedule, and activity levels, which vary from day to day.

Rather than focusing on open-ended deprivation and suppressing your healthy appetite signals, DDF shows you precisely when you need to eat.   

1.2 How DDF is Different from Calorie Counting

Managing calories in vs calories out sounds simple, but it is incredibly difficult to implement successfully over the long term.  The reality is that all calories count, but only if you can accurately count ALL the calories (which we can’t!).

Tracking is inaccurate, our energy needs change over time, and our lizard brain often finds a way to trick us into eating more.  Our subconscious survival instincts also don’t like to be controlled by an external force for too long which can prompt psychological disorders to develop. 

Data-Driven Fasting respects energy conservation by using your blood glucose as a fuel gauge to guide your meal timing to ensure that you are in a negative energy balance and moving towards your goals. 

Data-Driven Fasting uses your blood sugars to ensure you are achieving a negative long-term energy balance while still getting the nutrients you need when you eat.  In addition, this practice helps improve satiety and avoid overeating when you don’t need fuel.

While simply counting calories and staying under an arbitrary limit is often futile in the long term, adjusting what you eat to get enough protein and nutrients without excess energy from carbs and fat is critical to taming your appetite. 

The DDF app will guide you on what to eat and how to tweak your fat and carb intake to tame your blood glucose.  However, we focus on this a lot more in our Macros Masterclass.  For more detail, see

1.3 Are There Any Additional Benefits from Extended Fasting?

While there may be benefits of extended fasting, there are also potential risks and downsides.

Not many people enjoy abstaining from food for days, and skipping eating for days at a time can be hard to fit into a regular family routine. 

Even the most respected fasting gurus admit we don’t know what length of fasting is required to achieve the theoretical benefits or the minimum effective dose to produce meaningful results.  Is it 24 hours? Or 36 hours? Three days? Seven days? Or maybe 14 days to get the full benefits of autophagy? 

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

The bottom line is:

If you cannot control your food quality when you eat again after fasting, 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 by prioritising nutrient-dense food choices when you eat to ensure a long-term energy deficit that leads to optimal body composition.  Data-Driven Fasting guides you through optimising meal timing and enables you to focus on getting the nutrients you need with a sustainable routine over the long term. 

While there is plenty of talk about the benefits of fasting for autophagy, cancer, and Alzheimer’s disease, very few studies are available on humans to validate these theories.

There is some research on autophagy in rodents.  However, mice aren’t tiny humans. One day for mice is equivalent to around 40 days for humans. Therefore, the equivalent of a 24- or 36-hour fast in a mouse would kill many people as they starve to death. 

Another key difference is that while rats get the same chow no matter how often they eat, humans can eat whatever they want when hungry to replenish our energy stores quickly. 

You will see plenty of posts on social media detailing the specific times you need to fast to get certain benefits.  Meanwhile, the experts in the field still don’t understand the optimal length of fasting to achieve the benefits of autophagy.  

What we do know, however, is that all the conditions we are most concerned about are vastly improved by achieving and maintaining more optimal body composition.

As shown in the charts below, the relative risk of a range of cancers increases with 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 image below (from Waist-to-height Ratio Is More Predictive of Years of Life Lost Than Body Mass Index) shows that our overall mortality risk increases with a higher BMI.

Many people ask, “How many days should I fast?” But what you really need to know is, “How can I optimise my normal eating to ensure that I am moving towards an ideal body composition and staying below my Personal Fat Threshold over the long term?”

For more details, see:

1.4 Chasing Your Trigger vs a “Fasting Window”?

Rather than a rigid window of time where you eat whatever and as much as you want (or can), Data-Driven Fasting guides you to eat when you are hungry and refuel only when your body needs it.

If you eat more than you require, you will need to wait longer until you can eat next.  You quickly learn not to overeat so you can eat again sooner.  While limiting the amount of time spent eating is beneficial, many people consume a lot of energy in a short window, especially if they choose energy-dense, nutrient-poor, lower-protein foods. 

When guided by their blood sugar, most people progress with Data-Driven Fasting with two separate meals per day. In addition, most people find it much easier to get the protein and nutrients they need with two meals a day compared to one meal a day (OMAD) or more extended fasting regimes. 

Many people who transition from OMAD to two meals a day in DDF find they have increased energy levels and greater satiety, and their weight loss restarts after stalling out. 

With DDF, we encourage you to ensure your meals are truly ‘window worthy’ so they provide you with the nutrients you need to maximise satiety.  Nutrient-dense meals with less fat and carbs will help you return to your trigger and increase satiety per calorie. 

For more details, see:

1.5 What Is An ‘Extended Fast’?  How Long is Too Long?

While you may be able to go for weeks without food, it may not be the best way to achieve your long–term goals (e.g., weight loss and improving your metabolic health). 

For the many people who eat all day, a couple of hours may feel relatively ‘extended’.  Data-Driven Fasting will guide you to dial in your daily eating routine.  Most people land on a regular eating schedule with multiple meals each day.

There is nothing wrong with going 24 or 36 hours without food so long as you make good choices when you refuel to ensure you get the nutrients you require. 

Unfortunately, getting the protein and nutrients your body requires over the long term is nearly impossible with regular bouts of alternate-day fasting, extended fasting or even OMAD. 

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

1.6 How Is Data-Driven Fasting Different from The Fast-Mimicking Diet? 

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

In contrast, Data-Driven Fasting encourages you to adopt a Protein Sparing Modified Fast style diet when your blood glucose indicates you have plenty of fuel on board.  This ensures you obtain adequate bioavailable protein and other essential nutrients. 

When your glucose levels fall, indicating you need more fuel, the DDF app will encourage you to eat normally or even prioritise a few fast-acting carbs if your glucose levels drop too low. 

Maximising nutrient density (i.e., getting all the essential amino acids, vitamins, minerals and essential fatty acids you need with fewer calories) will ensure that your body gets what it needs during weight loss to optimise mitochondrial function, prevent the loss of metabolically active lean muscle mass and minimise cravings.

For more details, see Secrets of the Nutrient-Dense Protein Sparing Modified Fast (PSMF) Diet.

1.7 Would Waiting a Little Longer Be Better?  

When they start out, some people wonder if waiting a little longer to get a value that’s a few extra points below their trigger would be better. 

If a little deprivation is good, then more must be better, right? 

However, DDF aims to validate your hunger and induce an incremental progressive overload on your metabolism by stretching it a little bit further each time to ensure adaptation and recovery. 

Recovery is a critical but often undervalued component of any beneficial (hermetic) stress.  In DDF, the recovery component is nutrient-dense, high-satiety eating.  You don’t want to push your hunger too far to the point that you sacrifice diet quality when you eat again. 

We’re all impatient and want rapid results but pushing too hard too early tends to wake your lizard brain, and you end up eating more than you need to and making poorer food choices. Also, trying too hard in the first week will make it much harder to make consistent progress in the final weeks of the challenge. 

In the first few days of the Data-Driven Fasting Challenge, all you need to do is to learn to wait until your blood sugar is below what is typical for you.  We want you to get into the habit of testing when you feel hungry and to record it in the DDF App.  Once you master the basics, the intensity ramps up as your trigger drops to push you a little more each day, building on the new skills you developed in the first week.   

So, if you’re hungry and your blood glucose is below your trigger, you’re good to eat—there’s no need to be in a hurry or try too hard!  In the first few days, you will learn to eliminate unnecessary snacking and find an eating routine that works for your life and metabolism.  

It’s crucial that you get into the habit of testing your blood sugar to validate your hunger before it gets more challenging.

As you log more pre-meal glucose values below your current trigger, your trigger will decrease to ensure you continually move towards your fat loss goals and optimised blood glucose.  If you do this consistently, your trigger will continue to drop.  Don’t be in a hurry!  

1.8 Extended Fasting Could Harm Your Healthy Appetite Signals

Many people who have tried extended fasting have reported resultant challenges after losing touch with their healthy appetite signals.

Although we can push through hunger, this often leaves us unable to stop eating when we have had enough food.  Your survival instincts are on the alert for starvation again, so your appetite ramps up to make sure you eat more to ensure you never run out of fuel again. 

Your body LOVES routine.  It can be useful to compress your eating window to give your metabolism and digestion time to rest while repairing and using up your energy stores without continually being topped up. However, there is a risk that your lizard brain will get confused if you subject it to extended periods of fasting or irregular meal timings that are out of sync with your healthy appetite signals and need for food. 

If you go out and eat a big meal late on Friday night, sleep on Saturday and Sunday, and then go back to work on Monday with an early breakfast, your body gets metabolic jet lag.

Your circadian rhythm is affected by exposure to light and your activity and eating patterns. This rhythm helps to calibrate the schedule that your body follows to regulate its sleep/wake cycle, release hormones, and cue hunger.

It is ideal to eat most of your calories earlier in the day when the sun is up, and your body is primed to use the energy.  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 healthy appetite signals can become confused when you skip eating for days on end and then eat to satiety on others.  As you push through hunger on some days, you tell your lizard brain that food is scarce and to eat more than you need to the next time you eat to ensure that you have enough food for the next self-inflicted famine.

Hence, we strongly recommend you develop a regular eating routine guided by your blood glucose, not by some arbitrary time on the clock that may have worked for someone else’s lifestyle.  

DDF will use your instantaneous blood glucose to nudge and fine-tune your current eating routine without turning everything you currently do on its head.  Because your personalised blood glucose trigger is based on your typical blood glucose before you eat, waiting until your blood glucose drops below your trigger should only be a gentle stretch. 

1.9 Will I Be Getting Enough Autophagy with Data-Driven Fasting? 

While there is much talk about autophagy (i.e., self-eating or the body’s way of cleaning out old and damaged cells), when we don’t eat, there is very little understanding of the actual length of fasting required to achieve an optimal amount of autophagy. 

Unfortunately, studies on yeast and worms in a Petri dish aren’t the same as humans living in the real world, who also need to be robust and resilient to survive into old age. 

Research by Valter Longo has shown that cycles of 48-hour fasting produce benefits in mice. However, mice aren’t tiny humans. One day for a mouse is equivalent to 40 human days.  The equivalent of a 48-hour fast in a mouse (i.e., 80 days) would kill most humans.

Unfortunately, measuring autophagy in humans would be impossible to do. So, the reality is that we know very little about autophagy in humans or how long we need to fast to achieve it!  

But we do know that autophagy occurs all the time, to some extent.  However, it is particularly active when we are not overfed and in a negative energy balance over the long term.  Too much autophagy can be harmful if you lose precious lean muscle mass when you fast and don’t get enough dietary protein. 

People often refer to the case study of Angus Barbieri, who fasted for 392 days and came out thin and healthy.  However, they fail to mention the ten young men in their 20s who died after not eating between 46 and 71 days in the 1981 Irish Hunger Strike

Over time, extended fasting can worsen metabolic health, particularly if you don’t get enough protein and nutrients over the long term.  Common symptoms of extended fasting without adequate nutrition that can lead to weight loss plateaus include:

  • loss of lean mass,
  • hair loss,
  • fatigue,
  • dysregulation of healthy hunger signals,
  • adrenal dysfunction,
  • thyroid disorders, and
  • an inherently lower metabolic rate.  

While we know little about the benefits of autophagy in humans, we do know that achieving a more optimal body composition, body fat percentage, fasting blood glucose, and waist-to-height ratio are highly correlated with a reduced risk of dying of any cause. 

Cumulative small bursts of autophagy followed by nutrient-dense refeeds are more beneficial than occasional multi-day fasts followed by energy-dense, nutrient-poor bingeing that immediately reverses all the benefits of your self-inflicted deprivation. 

Data-Driven Fasting ensures you get smaller doses of autophagy as your critical metabolic markers (i.e., body fat, blood glucose, insulin, etc.) move towards optimal. 

1.10  Is Calorie Counting The Best Way to Lose Weight?

Many people try calorie counting using apps like MyFitnessPal.  But sadly, very few people achieve the long-term success they had hoped for. 

  • Most of us live unpredictable lives filled with family dinners, work lunches and impromptu parties that make weighing and measuring everything we eat impractical.
  • While we can be disciplined most of the time, it’s those occasional meals – when your calorie-tracking app isn’t looking – that sneakily undo all your hard work.
  • Even if you could weigh and measure everything you put into your mouth, the nutrition data in your app doesn’t precisely match the foods you eat. 
  • Your body doesn’t ‘burn’ foods in the same way that calories are measured in a bomb calorimeter (pictured below).
  • Calorie-tracking apps don’t account for the thermic effect of food, which varies depending on the degree of processing and macronutrient profile.
  • Any theoretical calorie target calculated by an online macronutrient calculator is an inaccurate ‘guesstimate’. 
  • Your energy expenditure naturally adapts and changes from day to day.  Your metabolism is incredibly complex.  Many factors influence the energy you use each day, including:
    • your muscle mass,
    • exercise,
    • stress,
    • activity,
    • age,
    • overall health, and
    • sleep. 
  • Eating is primal and instinctual. Your appetite ensures that you seek out the nutrients you need.  When you restrict calories, the part of your brain that governs your survival instincts (i.e., your amygdala, also known as your ‘reptilian’ or ‘lizard’ brain) perceives a starvation threat and responds to this ‘dire emergency’.  Your body responds by slowing your metabolism and driving up your hunger to ensure you eat more next time you have access to food. 
  • Despite your best efforts to limit the amount you eat, if you consistently fail to consume the nutrients your body requires, you can expect a hostile takeover by your ‘lizard brain’ as it hijacks your appetite.
  • If you try to maintain a fixed calorie intake, ignoring your healthy hunger signals on some days and eating more than you need on others, there is a real risk that your natural and healthy appetite signals will become dysregulated.  
  • When you slash your energy intake by simply restricting calories without changing WHAT you eat, your body quickly adapts to ensure your survival and:
    • your metabolic rate slows,
    • you produce less heat,
    • you feel less energetic, and
    • your involuntary activity grinds to a halt to divert energy to your heart, lungs, kidneys, brain, and other organs essential to your survival. 

Energy is always conserved.  However, the various factors on both sides of the ‘calories in vs calories out’ equation are incredibly complex and beyond our ability to precisely measure or manipulate, even with the latest smartphone app or activity trackers.   

While we would like to believe that our conscious brain is always in control and that we can use our willpower to eat less and move more, most people are unsuccessful at self-imposed starvation over the long term.

Prolonged fasting and very low-calorie diets eventually panic our ‘lizard brain’ into taking back control from our neocortex, rescuing us from what ‘Lizzy’ perceives as a starvation threat.

But fear not!  Data-Driven Fasting not only guides you, using the insights from using your blood sugar as a fuel gauge, to get to know and even make friends with Lizzy.   Data-Driven Fasting will show you how to tame your lizard brain by giving it exactly what it needs, precisely when it needs it.

Data-Driven Fasting is like a lullaby for a restless Lizzy—singing your inner lizard back to sleep, reassuring it that it will receive what it needs so that you can relax into a new routine, optimised just for you, and thrive!

1.11 Counting Calories Can Cause Disordered Eating

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

Eventually, frustration and anxiety mount when we discover that all the time and energy, we’ve invested in tracking everything we’ve put into our mouths has failed to yield the results we’d hoped for.

Sadly, chronic food tracking can cause many people to become neurotic. A 2017 study looking at people diagnosed with eating disorders found that 75% of participants reported using MyFitnessPal. Disturbingly, 73% of MyFitnessPal users said their use of the app had contributed to their eating disorder. 

Simply trying to count calories to stay under an arbitrary target is a recipe for failure.   The simplistic manifesto of ‘eat less, move more’ drives many dieters into a futile cycle of restrict, binge, restrict, binge, repeat.  Calorie tracking is as archaic as using an abacus without consideration of how your complex metabolism and appetite work. 

For more details, see Is Counting Calories and Caloric Balance a Waste of Time?