In the world of health and fasting strategies, Data-Driven Fasting (DDF) stands apart as a beacon of clarity amid confusion.
Since the inception of our Data-Driven Fasting Facebook Group in May 2020 and the subsequent Data-Driven Fasting 30-Day Challenges, we’ve witnessed a flood of inquiries from individuals seeking to decode the mysteries of their glucose signals.
The core of Data-Driven Fasting is elegantly simple: let your blood sugar meter be your guide. But as participants tiptoed into the realm of understanding how their blood glucose could guide their eating choices, they naturally found themselves brimming with questions. So, we created a comprehensive collection of Frequently Asked Questions (FAQs) to illuminate the path.
While you’re welcome to peruse it in advance, the real magic of learning happens experientially as you observe these principles unfolding before your eyes. Your journey will lead you to recognize your authentic hunger cues and make peace with your primal instincts, rendering your blood sugar meter a companion, not a crutch.
You’ll find that consistently following the process triumphs over sheer willpower every single time. Instead of battling to control your blood glucose levels and growing frustrated when they don’t conform, we invite you to embrace this process as a curious student would. Let the information from your blood glucose meter light your way forward.
Now, let’s delve into what truly sets Data-Driven Fasting apart from other fasting methods: the pitfalls of calorie counting, the mysteries of autophagy, and the wisdom of listening to your body rather than chasing arbitrary goals. Welcome to a transformative journey that blends science, intuition, and the art of understanding your body’s hunger using your glucose signals.
- 1.1 How is DDF Different from Other Fasting Methods?
- 1.2 Data-Driven Fasting vs. Calorie Counting
- 1.3 Are There Additional Benefits from Extended Fasting?
- 1.4 Chasing Your Trigger vs. a Fasting Window?
- 1.5 What Is An ‘Extended Fast’? How Long is Too Long?
- 1.6 How Is Data-Driven Fasting Different from The Fast-Mimicking Diet?
- 1.7 Would Waiting for a Little Longer Be Better?
- 1.8 Extended Fasting Could Harm Your Healthy Appetite Signals
- 1.9 Will I Be Getting Enough Autophagy with Data-Driven Fasting?
- 1.10 Is Calorie Counting the Best Way to Lose Weight?
- 1.11 Counting Calories Can Cause Disordered Eating
1.1 How is DDF Different from Other Fasting Methods?
Most approaches to fasting encourage you not to eat for days at a time in the hope of weight loss, reducing insulin and driving autophagy. In contrast, Data-Driven Fasting focuses on the long-term trend with shorter periods of ‘fasting’ interspersed by nutrient-dense refeeding to ensure your blood glucose and weight move in the right direction.
Like any intelligent fitness training routine that balances exercise and recovery, 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 harder than your body is used to, you’ll be sore and tired for days. So, you’ll be less likely to return the next day to work out. Without consistency, it’s hard to make progress over the long term.
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.
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 eating routine to your unique metabolism, schedule, and activity levels, which vary from day to day.
1.2 Data-Driven Fasting vs. 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 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.
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.
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. For more details, see
- Is Counting Calories and Caloric Balance a Waste of Time?and
- What Are Macros in Your Diet (and How to Manage Them)?
The DDF app will guide you on what to eat and how to tweak your fat and carb intake to tame your blood glucose. After a few rounds of Data-Driven Fasting, many people realise they need a bit more help to dial in their balance of protein, fat and carbs, which we cover in the Macros Masterclass. Later, when it’s time to dial in your food quality, our Micros Masterclass will help you optimise your diet at the micronutrient level.
1.3 Are There Additional Benefits from Extended Fasting?
While there may be benefits of extended fasting, there are also many potential risks and downsides.
Not many people enjoy abstaining from food for days. Skipping eating for days can be hard to fit into a regular family routine.
Even the most respected fasting gurus admit we don’t know the length of fasting 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. 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 to optimise your meal timing while ensuring you get 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 we’re hungry to replenish our energy stores quickly. Thus, we undo many benefits of extended fasting when we refeed on energy-dense, nutrient-poor foods due to extreme hunger.
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:
- Optimal Body Weight for Health & Longevity (and How to Achieve It)
- Nutrient-Dense Foods and Recipes for Cancer Patients,
- Can Longevity Be Bought in a Bottle? Thoughts on David Sinclair’s Lifespan,
- Personal Fat Threshold Model of Insulin Resistance, Diabetes and Obesity vs. the Carbohydrate Insulin Model, and
- What Is Insulin Resistance (and How to Reverse It)?
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, we can also consume a lot of energy in a short window, especially if we choose energy-dense, nutrient-poor, lower-protein foods.
When guided by their blood sugar, most people progress with Data-Driven Fasting with two meals or three meals a day.
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.
If you keep an eye on portion sizes, it’s definitely possible to get three meals a day while still losing weight.
So, Data-Driven Fasting is not really ‘fasting’ in the normal sense; it’s glucose-guided eating to ensure you validate your hunger and give your body exactly what it needs when it needs it!
Many people transitioning from OMAD to two meals a day in DDF 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 ‘window worthy’ to provide 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:
- How to Use Your Glucose as a Fuel Gauge (A Pictorial Guide),
- Highest Satiety Index Meals and Recipes,
- High Satiety Index Foods: Which Ones Will Keep You Full with Fewer Calories?
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 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 uses your blood glucose to optimise your eating routine. As a result, 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 OMAD. So, if you find yourself reaching for the peanut butter, nuts, cream, or pizza 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 is similar to a Protein Sparing Modified Fast type 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 for a Little Longer Be Better?
When they start, some people wonder if waiting a little longer to get a value a few extra points below their trigger would be better.
DDF aims to validate your hunger and induce an incremental progressive overload on your metabolism by stretching it just each time to ensure adaptation and recovery. Because they haven’t given their metabolism a chance to adapt, people often find it too hard to reach their glucose trigger after a few weeks when they push too hard too early.
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, you learn to wait until your blood sugar is just below what is normal 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 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 progress towards your fat loss goals and optimise blood glucose. If you do this consistently, your trigger will continue to drop to ensure you continue to make progress.
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 ensure you eat more and never run out of fuel again.
Your body LOVES routine. 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 your body’s schedule to regulate its sleep/wake cycle, release hormones, and cue hunger. So eating most of your calories earlier when the sun is up and your body is primed to use the energy is ideal.
Similarly, your healthy appetite signals can become confused when you skip eating for days and then try to 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 the next time you eat to ensure 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.
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 must also 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 is impossible. So, 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. 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 don’t get enough protein.
People often refer to 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.
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 include:
- weight loss plateaus,
- loss of lean mass,
- lowering your metabolic rate,
- hair loss,
- dysregulation of healthy hunger signals,
- adrenal dysfunction,
- thyroid disorders, and
- a 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 refeeding is 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 regular 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 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 like 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 (even ours) 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,
- overall health, and
- 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 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 apps 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 simply 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 counting calories an trying 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?
- Data-Driven Fasting: How to Use Your Blood Glucose as a Fuel Gauge
- Join the next Data-Driven Fasting Challenge
- Try the Data-Driven Fasting app
- Get the DDF Manual
- Join Our Community
- QuickStart Guide
- The DDF app User Guide
- Frequently Asked Questions