Unlock Your Metabolic Potential with Data-Driven Fasting

Dive into the realm of Data-Driven Fasting with this insightful guide. Explore how tracking your progress is crucial in managing blood glucose levels, whether you’re on a weight loss mission or striving for metabolic excellence. Uncover the science-backed strategies to optimize your health journey starting today.

3.1 Are My Blood Glucose Levels Before or After I Eat More Important?

Most people focus on limiting the rise in their blood glucose after eating by lowering carbohydrates and sometimes even protein.  However, rather than micromanaging the rise in glucose after you eat, it’s the average blood glucose across the whole day that matters.  As you will see, the most effective way to reduce your average glucose across the day is to manage your glucose levels before you eat.

The period after you eat is only a tiny portion of the day.  High-fat meals that only cause a slight rise in blood sugar after eating can keep blood glucose elevated for longer. Thus, increasing fats may not help you achieve a long-term reduction in your average blood glucose across the day, nor will it help with fat loss or reduce your insulin levels.

As shown in the diagram below, while carbs raise blood sugars and insulin over the short term, dietary fat will elevate your blood sugars over the longer term and prevent them from falling.  Thus, to reduce the area under the curve of insulin and blood glucose, dial back fat and/or carbohydrates and wait a little longer to eat until your blood glucose drops below what is typical for you. 

Modifying your diet to reduce the rise in blood glucose after you eat is only one step in the journey.  Delaying meals until your blood glucose is below your trigger ensures your average blood glucose decreases and your stored body fat is used for fuel. 

As shown in the chart below from our data analysis from people using the DDF app, there is a strong correlation between premeal glucose and waking glucose, a key marker of overall metabolic health. 

Large swings in glucose after you eat are not ideal.  This can occur when you consume more carbohydrates than your body needs. Significant rises in blood glucose (e.g., more than 30 mg/dL or 1.6 mmol/L) can result in your glucose crashing back down and increased hunger (i.e., reactive hypoglycaemia). 

However, if your glucose rise after meals is in the normal healthy range, there is no benefit in trying to reduce it more.  As shown in the chart below, there is little correlation between waking glucose and the rise in glucose after meals.  Hence, focusing on managing your glucose before eating is much more helpful. 

In the Data-Driven Fasting Challenge, we will guide you through the following steps:

  1. Dial back refined carbs to achieve non-diabetic blood glucose variability. After most meals, your blood glucose should not rise more than 30 mg/dL or 1.6 mmol/L.  
  2. Fine-tune your meal timing using Data-Driven Fasting to continue the fat-loss journey.  
  3. If you are not achieving weight loss or your waking blood glucose is not decreasing with a Main Meal and a Discretionary Meal, look to increase your protein percentage, food quality, and nutrient density by reducing the foods that provide the most fat in your diet.
StepLimitDescriptionWhen to progress
1. Stabilise blood glucose< 30 mg/dL or 1.6 mmol/L rise after mealsReduce processed carbs to achieve healthy blood glucose stability.When typical BG rise after meals is < 1.6 mmol/L or 30 mg/dL
2. Meal timing/intermittent fastingOne Main Meal with one Discretionary Meal (OMAD+)Reduce the number of times you eat per day.  When average meals per day is less than 1.5. 
3.  Increase protein % by dialling back fatWork up to at least 40% protein.Slowly increase protein % (by reducing dietary fat) until weight loss re-commences.When you have reached goal weight, body fat, waist:height or waking glucose. 

3.2 How Quickly Will I Lose Weight with Data-Driven Fasting? 

The rate of weight loss with Data-Driven Fasting can be quite rapid if you can wait until you are below your pre-meal trigger to eat most of the time and dial up the protein % of your meals.  However, we’d rather you form consistent habits than compete for the top of a short-term weight-loss leaderboard. 

Greater compliance will lead to faster weight loss.  However, finding a sustainable routine is critical rather than pushing so hard that you are bingeing due to excessive hunger, which will derail your long-term progress.  

The chart below shows that some people lose more than 1.0% of their weight each week.  However, if you consistently lose more than 0.5% weekly, you do not need to try harder. 

For more details on why we suggest a sustainable rate of weight loss of 0.5 to 1.0% per week, see How Much Weight Should I Lose Per Week? 

You can also check out the spectacular results from our previous challenges here

3.3 Should I Track My Weight When Fasting?

You don’t have to track your weight daily in the Data-Driven Fasting Challenge.   

Because the amounts of water and food change in your gut, your body weight can change daily.  While knowledge is power, some people find that tracking their weight AND blood glucose becomes too much of a mind game.

Some people love all the data and find daily weighing keeps them accountable.  However, others find the data is too much.  It’s easy to overthink the day-to-day fluctuations, leading to burnout.  

So, tracking your weight each morning to see the trends is ideal.  But if you find this challenging, you only need to log your weight once per week to ensure you are making progress over time.   

3.4 How Often Should I Measure My Waist?

As shown in the chart below, a waist-to-height ratio of less than 0.5 indicates optimal metabolic health. We recommend you track your waist circumference each week on Sundays. 

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

You can also record your waist in the DDF app.

3.5 What Are Optimal Body Fat Levels?

Your pre-meal blood glucose will decrease as you reduce body fat levels below your Personal Fat Threshold.  Your blood glucose meter can provide insight into whether you carry excess fat, regardless of weight. 

A bodybuilder may still be healthy despite having a high Body Mass Index (BMI) so long as they are not carrying too much fat. But even bodybuilders can gain too much fat in their pursuit of strength and see their blood glucose rise. Being strong doesn’t necessarily mean you have excellent body composition or 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 health.  As you reduce your body fat levels to fitness and athlete levels, you will find that your blood glucose naturally starts to decrease towards optimal levels. 

Essential fat10-13%2-5%

The pictures below show what this looks like visually.   

Aside from losing body fat, it’s also important to do whatever you can to preserve your lean mass (i.e., muscle).  Your lean mass is metabolically active and ‘burns calories’.  Like a fuel-efficient race car or sprinter, resistance training will help increase your power-to-weight ratio so you use energy from food more efficiently. 

People who lose excessive lean mass often find it extremely hard to sustain their weight loss because their metabolic rate has slowed.  As a result, they must maintain a VERY low-calorie intake to avoid rebound weight gain.  Before long, this becomes unsustainable. 

As mentioned in this video by Dr Ted Naiman, morbid obesity and Type2 Diabetes are on the opposite side of the spectrum from a lean and muscular bodybuilder.  While it’s not necessarily healthy or sustainable to have extremely low body fat levels, many of us need to move in that direction by losing body fat and gaining lean muscle mass. 

While gaining strength and increasing your lean mass is a worthwhile goal, it can be hard to do while also losing weight.  You should continue your program alongside Data Driven Fasting if you work out.  However, we don’t suggest you start an aggressive lifting program while trying to lose weight, as it can lead to dysregulated blood glucose levels and increased appetite.   

During the Data-Driven Fasting Challenge, your goal should be to preserve your lean mass by prioritising protein at meals.  In addition, being active and lots of lower intensity activity like walking will tend to lower glucose and use more fat without significantly increasing appetite.  For more details, see Optimising Your Exercise [Macros Masterclass FAQ #7].

3.6 What Is the Ideal Blood Sugar Level for Weight Loss?

There is no perfect one-size-fits-all blood glucose level for weight loss. 

In the DDF challenge, you aim to chase a lower premeal blood sugar before eating.  Waiting a little longer and making better food choices that allow your glucose to return below your trigger sooner will lead to fat loss. 

Generally accepted fasting (i.e., first thing in the morning) and post-meal blood glucose ranges are shown in the table below.  Once your waking blood glucose is below 100 mg/dL or 5.6 mmol/L, you can rest assured you are under your Personal Fat Threshold and minimise your risk of diseases associated with energy toxicity and metabolic syndrome. 

   fastingafter mealHbA1c
Normal< 100< 5.6< 140< 7.8< 6.0%
Pre-diabetic100 – 1265.6 to 7.0140 to 2007.8 to 11.16.0 to 6.4%
Type 2 diabetic> 126> 7.0> 200> 11.1> 6.4%

For more details from our analysis of half a million blood glucose data points logged in the DDF app, see:

3.7 How Do I Find My Personal Fat Threshold? 

Your Personal Fat Threshold is the level of body fat that your body is comfortable storing in your adipose tissue without overflowing into your vital organs.  Being above your Personal Fat Threshold leads to fat being stored in vital organs like your liver and fat and glucose overflowing into your bloodstream.

The only way to find your Personal Fat Threshold is to lower your weight so that your waking glucose is in the normal healthy range when you are weight stable.  For some people, this may be at a waist-to-height ratio of 0.5, while others may need to be slightly lower.

Once you reach your goal weight, switch to ‘Maintenance Mode’ in the DDF app. Then, if you regain weight in the future, you can restart the process to get your waist and glucose levels back in this range.     

3.8 What Is the Best Way to Measure Body Fat? 

Tracking your body fat percentage helps ensure you lose fat rather than precious and metabolically active lean muscle mass. The last thing you want is to lose muscle and end up looking like a fat skeleton with a low metabolic rate that has to maintain an extremely low-calorie intake to keep weight off! 

There are many ways to measure body fat.  None are perfectly accurate, but they’re still helpful for tracking your long-term trend. 

  • A DEXA scan is the most accurate but expensive and inconvenient, so you are unlikely to do it regularly. 
  • The Navy Fat calculator is surprisingly accurate and aligns with DEXA scan measurements. It is based on your waist, hip, neck, and weight measurements. 
  • The most convenient way to measure body fat is through bioimpedance, which can be measured with most modern scales.  These may not be as accurate as DEXA, but they will ensure you are heading in the right direction over the long term.    

If you look leaner and healthier, you probably are.  In our Macros Masterclass, we use body fat and lean mass measurements to dial in your macronutrient balance using our Smart Macros Algorithm.  However, body fat measurements are not critical for Data-Driven Fasting. Your waist measurement and selfies will be adequate if you don’t already have a bioimpedance scale.  

For more details, see What Do the Numbers on My Bioimpedance Scale mean (and How Can I Manage Them)?

3.9 Can I Lose Fat and Gain Lean Mass at The Same Time?

While most people lose some lean muscle mass when losing weight, we have seen several people manage to gain lean mass while losing fat mass when they increase their protein intake. 

The best ways to minimise the loss of lean mass while losing weight are:

  • consuming enough dietary protein,
  • resistance training to tell your body to maintain its muscles and
  • getting good sleep, resting adequately, and reducing stress.

For more details, see Secrets of the Nutrient-Dense Protein Sparing Modified Fast (PSMF) Diet and Optimising Your Exercise [Macros Masterclass FAQ #7].

3.10 Do I Need to Check My Blood Glucose Before Every Meal?

While some people love ALL the data, we have designed Data-Driven Fasting to allow people to use the minimum effective dose of testing and tracking to maximise long-term sustainability. 

In the Data-Driven Fasting 30-Day Challenge, you can identify your ‘Main Meal’ that you know you eat at a regular time each day.  For example:

  • dinner with your family,
  • a protein-packed breakfast in the morning, when many people find their glucose higher or
  • after your workout when you require extra fuel, and your blood sugars can be elevated due to intense exercise. 

You can then use your blood glucose to decide whether you eat at other times throughout the day (i.e., ‘Discretionary Meals’).   If you want, you can skip testing your glucose before the main meal and only test before the discretionary meals. 

But remember, while you can ‘lie’ to your calorie tracking app, you can’t ‘cheat on’ your blood sugar.  It always tells the truth based on what you have been eating.  So, it’s ideal to track your premeal blood sugar as often as possible and take evasive action before things get out of hand. 

3.11 How Do You ‘Build Your Fasting Muscle’?

Many people talk about ‘building their fasting muscle’ as if they need more willpower or do it longer and harder to get more benefits.

But sadly, most people go too hard too early and burn themselves out before building new habits or a sustainable routine that will provide long-term benefits when it comes to fasting and exercise.

Building a healthy eating pattern is like building an intelligent workout routine.  You need to do the right exercise at the right time, not overdo it, recover adequately with nutrient-dense refuelling, and get the minimum effective dose by measuring your progress.

It’s crucial to build Tiny Habits and celebrate small successes yielding sustainable lifestyle changes that lead to achieving your ultimate goal. 

To help you achieve this, Data-Driven Fasting provides a systematic approach to ensure you address these critical elements to ensure long-term sustainable success. 

  • By measuring your pre-meal blood glucose, you ensure you are doing the right exercise by finding the right balance between delaying your first meal and finishing eating earlier.
  • By prioritising high-satiety, nutrient-dense food, you maximise your recovery and are ready to fast again sooner.
  • Waiting to eat when your glucose falls below your trigger ensures you get the minimum effective dose without overdoing it.
  • By tracking your blood glucose, weight, and waist measurements, you ensure you are making progress and rewarding yourself for your effort as you progressively lower your trigger.

3.12 What Are Ideal Blood Sugar Levels for Weight Loss? 

There is no absolute value that corresponds to fat burning.  This is because you are constantly using a combination of fat and glucose. 

But as your blood glucose drops, you will be using more fat.  So, if you are not overdoing dietary fat, you will be using the fat from your body.

The chart below shows a compilation of pre-meal vs. waking glucose values from people who have completed the Data-Driven Fasting 30-Day Challenge, showing that a lower premeal blood glucose correlates with a lower waist-to-height ratio. 

As you chase a lower premeal glucose level in the challenge, you should expect to see a reduction in body fat and waist circumference. 

The charts below show how premeal glucose (in mmol/L and mg/dL) corresponds with waking glucose, a critical metabolic health marker. 

For more details, see What Is the Ideal Blood Sugar Level for Weight Loss and Fat Burning?

3.13 Does the DDF App Have a Lower Limit for Blood Glucose? 

Some people see their blood glucose fall when they begin Data-Driven Fasting and wonder how low is too low and if the DDF app has a lower glucose limit. 

The answer is no.  The DDF App doesn’t have a lower limit for blood glucose, but your body does.  But, because DDF encourages you to eat before your glucose gets too far below your current trigger, very low glucose levels should be rare. 

The charts below show the range of premeal blood glucose values in people undertaking the Data-Driven Fasting Challenge.  Some people see their blood sugar levels get down to 60 mg/dL or 3.5 mmol/L.  However, most people will have reached their weight loss or body fat goals before they reach this point.   For more details, see What are Normal, Healthy, Non-Diabetic Blood Sugar Levels?

While these values are much lower than what passes for ‘normal’ in a world awash with diabetes, there is no issue if you are not taking medications to actively lower your blood glucose (e.g., injected insulin, metformin, etc.) and feel OK.  

Once you reach a waist-to-height ratio of less than 0.5 and a waking glucose of less than 100 mg/dL or 5.6 mmol/L, we suggest you transition to maintenance.  

After each round of the Data-Driven Fasting Challenge, we encourage people to take a break to practice maintenance until they are ready to push again.  You shouldn’t keep pushing if you can’t successfully maintain your reduced weight for a few weeks between challenges. 

Because Data-Driven Fasting guides people to delay or skip their meals rather than fasting for days at a time, we don’t tend to see people having the same issues that are more common with prolonged fasting or aggressive dieting. 

As you chase your premeal blood glucose trigger, your body will adapt to using fat rather than glucose to fuel.  So, you’re much less likely to be symptomatic at a lower blood glucose level. 

But if it’s getting hard, we recommend transitioning to Maintenance Mode in the DDF app until your lizard brain settles down and you are no longer food-focused.  You can always jump back into another round of the Data-Driven Fasting Challenge when you feel you are ready.    

The break between challenges is an integral part of the process to allow your body to find new homeostasis at a new level and your blood sugar to be refilled from the stored energy in your body and a little bit more food.

Don’t be concerned if your new trigger is slightly higher than where you left off at the end of the last challenge.  While your glucose may not fall much more as you chip away at your trigger for 30 days, you will continue to use your stored energy for fuel.  Muffy’s premeal glucose chart shows what this can look like over the long term, with success rounds of the DDF challenge. 

3.14 Will I Lose Too Much Lean Mass When I Fast?

While many focus on weight loss, loss of metabolically active lean mass (i.e., your muscles and organs) is an unfortunate reality for people maintaining a long-term energy deficit, particularly as we age. 

Encouraging people to fast for extended periods, telling them that nutrients and protein don’t matter, and then saying that they shouldn’t binge when they refuel is like taking someone to the top of a mountain where the air is thin, making them hold their breath for longer than they ever have, and instructing them not to gasp when they take their next breath.

If you want to build strength and resilience in anything, you need to increase the intensity at a sustainable rate (i.e., progressive overload) while ideally using some form of measurement to ensure you are making incremental progress and progressively adapting. 

Data-Driven Fasting encourages people to track their body fat in the DDF app, using at-home bioimpedance scales to understand their long-term trend in fat loss vs. lean mass. While bioimpedance scales are not perfectly accurate, tracking changes in body composition over time can still be helpful and cost-effective.  You should also introduce some form of resistance training to signal to your body that you want to grow and maintain muscle despite losing fat. 

If your lean mass is trending down faster than you would like or your body fat percentage increases, you can review your diet to ensure you consume adequate protein and try to be a little less aggressive.  

To ensure they get adequate protein and nutrients without excess energy from fat and carbs, many people find our Macros Masterclass a helpful next logical step after they complete a few rounds of the Data-Driven Fasting Challenge

3.15 Should I Record My ‘Pre-Meal Blood Sugars’ When I Don’t Eat?

If you test and decide not to eat, you can uncheck the ‘did/will you eat?’ box in the DDF app (as shown below).  This will record your glucose value in the app and show on the chart, but it won’t be used in your trigger calculations. 

You may find you take a few extra blood glucose readings while waiting for your blood glucose to drop below your current trigger, especially in the first few days of Hunger Training.  In time, you will learn how your hunger symptoms align with your blood glucose without testing until you are hungry. 

3.16 When Should I Check My Waking Blood Glucose?

While you can track your waking glucose every day in the DDF app, you only really need to do it:

  • during baselining,
  • in the final three days of the challenge and
  • during the eating window stage (days 11 to 17).

Other than these times, feel free to skip checking your waking glucose if it’s a hassle or if you find it confusing.

Regarding the time of the day, it should be taken after you get up before eating or drinking anything.  We suggest you integrate it with your morning routine of going to the toilet, weighing yourself, taking your morning blood sugar, and making coffee or tea.  What matters here is consistently integrating it into your routine rather than the exact time.

3.17 How Often Do I Have to Test My Blood Glucose?

You only need to test your blood glucose to validate your hunger before eating.  This could be as little as twice a day, or even less if you identify your Main Meal regardless of your blood sugar.  

We would also like you to test your post-meal glucose during baselining and waking glucose at the start and during the eating-window stage.  However, most people quickly find that their post-meal blood glucose is generally in the normal healthy range after eating, so there’s little value in testing after meals. 

The table below shows the recommended minimum effective dose of testing and tracking that we recommend during the Data-Driven Fasting 30-Day Challenge.   Any additional blood sugar readings are optional. Some people like all the data, but we recommend adopting the minimum effective dose of testing to guide your eating schedule. 

3.18 Will DDF Work With OMAD?

While we usually find people settle on a schedule of three/two or two/one meals per day.  Because most people are unable to get adequate protein and nutrients in one sitting, we don’t recommend OMAD or ADF.   

If you find you are only able to reach your trigger once per day, we suggest trying:

  • a protein-focussed meal earlier in the day when you’re hungry, but blood sugars are still elevated and
  • increasing your protein % to at least 40% (by dialling back dietary fat and carbohydrates). 

Once they do this, most people find themselves fuller after each meal and able to reach their trigger twice a day while still losing weight. 

3.19 What If Blood Glucose Testing Is Getting Too Expensive or Painful?

While using your blood glucose is the most powerful way to understand if you need to refuel, you may find testing becomes expensive, 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 hungry to test. Over the first week or so, you will get a feel for when your blood glucose is lower.  After that, testing will become less of a novelty, and you will test less frequently.  For example, if you’re eating only two or three times a day, you only need to do two or three tests. 
  • It’s ideal to have regular mealtimes rather than eating haphazardly based on blood glucose.  After a few days of Data-Driven Fasting, most people find they eliminate snacking and drop back to a regular schedule of two or three meals a day.  Before long, you will identify your typical eating routine that works for your metabolism, activity and routine.  You can then test when you know you have the opportunity to eat and then fine-tune what and how much you eat based on your blood glucose levels. 
  • On Day 10 of the Data-Driven Fasting 30-Day Challenge, we guide people to lock in their Main Meal (the meal you eat regardless of blood glucose) and treat other meals as discretionary based on their blood glucose. 
  • If you typically have three or four meals daily and find your blood glucose elevated before eating one, skip that meal and don’t test until the next meal.
  • You can skip-testing your waking glucose.