Tracking Your Progress [Data Driven Fasting FAQ Part 3]

This section of DDF FAQs addresses the most common questions that arise when people start tracking their blood sugars in pursuit of weight loss, reduction in body fat, diabetes reversal or improved body composition.

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, it’s the average of your blood glucose across the whole day that really matters.  And 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 keep your blood sugars elevated over the longer term and prevent them from falling.  Thus, to reduce the area under the curve of insulin and blood glucose, you need to 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. 

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

  1. Dial back refined carbs to achieve non-diabetic blood glucose variability. Your blood glucose should not rise more than 30 mg/dL or 1.6 mmol/L after most meals.  
  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. Nonetheless, we’d rather you form consistent habits than compete for the top of a short-term weight-loss leader board. 

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

As shown in the chart below, some people lose more than 1.0% of their weight each week.  However, if you’re consistently losing more than 0.5% per week, there’s no need to try harder.

For more details, see:

3.3 Should I Track My Weight When Fasting?

You don’t have to track your weight every day.  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 simultaneously becomes a mental struggle. 

Some people love all the data and find daily weighing keeps 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 burnout.  

It’s ideal to track your weight each morning to see the trends. But if you find this to be 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 that your metabolic health is approaching optimal. Your waist measurement doesn’t change quickly, so you only need to measure it weekly. 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.  

3.5 What Are Optimal Body Fat Levels?

Your pre-meal blood glucose will continue to decrease as you reduce body fat levels to below your Personal Fat Threshold. Your blood glucose meter can provide an insight into whether you are carrying excess fat, regardless of your 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 gain lean mass (i.e., muscle) through exercise activities like resistance training. It’s your lean mass that 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 amounts of lean mass during fasting often find it extremely hard to sustain their weight loss because their metabolic rate has slowed. They must maintain a VERY low-calorie intake to avoid rebound weight gain. 

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 levels of body fat, many of us need to move in that direction by losing body fat and gaining lean muscle mass. 

3.6 What Is the Best Blood Sugar Level for Weight 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. 

3.7 How Do I Find My Personal Fat Threshold? 

The only way to find your Personal Fat Threshold is to lower your weight to the point 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 go a little bit lower.

Once you reach your goal weight, you can switch to ‘Maintenance Mode’ in the DDF app. 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 to track progress. 

  • 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 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 your 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.  

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

While most people tend to drop lean muscle mass when losing weight, we have seen several people manage to gain lean mass while losing fat mass if they significantly 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.

See Secrets of the Nutrient-Dense Protein Sparing Modified Fast (PSMF) Diet for more details.

3.10 Do I Have 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, like dinner with your family or a protein-packed breakfast. You can then use your blood glucose to decide whether you eat at other times throughout the day (i.e., ‘Discretionary Meals’).  

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

3.11 How Do You ‘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 benefits. But sadly, the majority of people go too hard too early and burn themselves out before developing a sustainable routine that will provide long-term benefits when it comes to fasting and exercise.

To develop a successful fasting routine, you should ensure you are doing the right exercise at the right time, not overdoing it, recovering adequately with nutrient-dense refuelling, and getting the minimum effective dose by measuring your progress. We strongly believe it’s crucial to build Tiny Habits and celebrate small successes yielding sustainable lifestyle changes that lead to achieving your ultimate goal. 

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

  • By measuring your waking and pre-meal blood glucose across the day, 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 from fasting, so you are ready to fast again sooner.
  • Waiting to eat when your glucose falls just below Your trigger ensures you are getting the minimum effective dose without overdoing it to the point that you will binge due to rebound hunger.
  • By tracking your blood glucose, weight, and waist measurements, you will ensure you are making progress and rewarding yourself for your effort as you progressively lower Your trigger.

3.12 Do I Need to Track Before Every Meal or Every Day?

You don’t need to log every meal for Data-Driven Fasting to work. However, you will get the most benefit from measuring more often to guide your routine and learn about your unique metabolism, especially when you start out. After a while, you will build new habits and get a better appreciation for your true hunger signals. 

You may want to lock in your Main Meal and only test before Discretionary Meals. If you are on holiday 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 out if you have overfilled your fuel tanks while you weren’t tracking. If you have already drained a little bit of your excess fat stores, it won’t take as long to catch up to your trigger.

3.13 What Are Ideal Blood Sugar Levels for Weight Loss? 

There is no absolute value that corresponds to fat burning.  You are constantly using a combination of fat and glucose.  As your blood glucose drops, you will be using more fat.  If you are not overdoing dietary fat, the fat you are burning will be 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 your waist circumference.


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

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

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

While the DDF app doesn’t have a lower limit for blood glucose, your body does. 

The chart below shows the range of blood glucose values we see in people undertaking the Data-Driven Fasting Challenge.  Some people see their blood sugar levels below 70 mg/dL or 3.9 mmol/L.  However, most people will have reached their weight loss or body fat goals before they reach this point.  

Once you reach a waist to height ratio of less than 0.5, a waking glucose of less than 100 mg/dL or 5.6 mmol/L, we suggest you transition to maintenance unless you really want to get super lean and drive your body fat to potentially unsustainable levels. 

This is not recommended, particularly if you are feeling particularly food focussed, weak or tired.  If you feel unwell (e.g., overly lightheaded, weak, etc.), you should eat. 

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. 

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

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 a new homeostasis and allow their blood sugar to be refilled from the stored energy in your body and a little bit more food. So don’t be concerned if you find that 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. 

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

While many people simply 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. 

Encouraging people to fast for extended periods and 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 telling 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 it to or your body fat percentage increases, you can review your diet to ensure you are consuming adequate protein.  If you’re interested in dialling in your macronutrient balance, you can try our Macros Masterclass as the next step after you finish the Data-Driven Fasting Challenge

3.16 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). 

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 having to go to the effort of testing until you are actually hungry. 

3.17 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.

In terms of the time of the day, it should be taken before you eat or drink anything.  Some people like to take it before getting out of bed, but you don’t have to. We suggest you integrate it with your morning routine of going to the toilet, weighing yourself, taking your morning blood sugar, and making your coffee or tea. All that really matters here is consistently integrating it into your routine rather than the exact time.

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

For the most part, you should only test your blood glucose to validate 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 also like you to test your post-meal glucose during baselining and your waking glucose at the start, during, and end of the eating-window stage. 

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

3.19 Will DDF Work With OMAD?

While we usually find people settle on a schedule of three/two or two/one meals per day, DDF will also work with one meal a day (OMAD).  If you are comfortable skipping full days of eating, you can treat your one meal a day as your Discretionary Meal and simply log your pre-meal blood glucose when you eat it.  If you can’t reach your trigger for a day during your usual mealtime, you could choose to skip it and wait for your blood glucose to come down tomorrow. 

However, keep in mind that food quality becomes even more critical with OMAD.  So you should do what you can to maximise food quality and nutrient density to ensure you get what your body needs long term. For example, our analysis has shown that we are able to consume a lot more calories per day on a higher fat, lower protein diet that is more energy-dense. 

Before resorting to skipping full days of eating, we recommend you increase your protein % to at least 40% (by dialling back dietary fat and carbohydrates).  Once you do this, you’ll find yourself fuller after each meal and able to eat two more times a day while still losing weight. 

For more details, see Low Energy Density Foods and Recipes: Will They Help You Feel Full with Fewer Calories?

3.20 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. Testing will become less of a novelty, and you will test less frequently. If you’re only eating two or three times a day, you only need to be doing 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.
  • In 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 per day and find your blood glucose elevated before eating one of those meals, skip that meal and don’t test until the next meal.
  • While tracking waking glucose is helpful to ensure that you are not eating too late, it can also be confusing when your insulin levels drop, and you are losing weight despite a rise in waking blood glucose. Feel free to skip the waking blood glucose testing if that is the case. You can always recheck your waking glucose once you are weight stable.