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How Scale Weight After a Refeed Changes Over Time

Chris Dunkerley — Sat, 11 Apr 2026 08:34:50 GMT

When you first begin intermittent fasting, the scale is a trusted tool that shows true results. But as fasting time frames normalise and extend, training is layered on top, and appetite and nutritional requirements change, the scale can become one of the most misleading tools you use.

One pattern I've discovered during this experiment, is that just because something previously worked, doesn't mean it always will.

The same can be said for the scales. For me, they have become a tool which fluctuates in accuracy and usefulness. But I'll get to that.

At the start of this plant performance, fasting experiment, the scales would often lie the morning after an evening refeed (the first meal after a fast).

You eat well, and refuel properly.
Then the next morning… your weight is up.

The extent to which will depend on;

how long your fast has been,
how heavily you have trained during it,
what you ate in your refeed.

Without understanding these variables, it's easy to let doubt creep in.

But this isn’t a failure of the system.

It’s a misunderstanding of what the body is actually doing.

Key Insights

A sudden weight increase after eating is usually water, not fat
Glycogen replenishment quickly pulls water back into the muscle
Sodium, carbohydrates, and timing all influence scale fluctuations
Plant-based refeeds can amplify this effect due to carbohydrate density
Short-term scale spikes often precede performance improvements
Misreading these signals leads to unnecessary restriction, and worse outcomes

Remember: This and other articles here, reflect personal experimentation and (are) not medical advice.

What the Scale Is Actually Showing You

After a structured refeed, your body is not gaining fat overnight.

It’s restoring.

When you fast, glycogen stores are depleted.
When you refeed, especially with carbohydrates, those stores refill.

And glycogen doesn’t come back alone.

For every gram of glycogen stored, your body pulls in 3 grams of water alongside it.

That means the scale can jump quickly, even when body fat hasn’t changed at all.

If anything, this is a sign the system is working.

Take a look at this blog which explains how glycogen use affects water retention and urination timing.

Why This Effect Can be Stronger on a Plant-Based (Vegan) Diet

If you’re eating plant-based, this effect can be even more pronounced, because most whole plant foods are:

Higher in carbohydrates
Higher in fibre
Lower in fat

This combination drives efficient glycogen replenishment, and with it, water retention.

Meals built around:

Rice
Oats
Lentils
Fruit

…will naturally refill glycogen faster than higher-fat alternatives.

Which means the scale response can look more dramatic.

But again, this is not fat gain.

It’s fuel being restored.

Sample Scale Data from my Experiment

Week 3

Date range: 1st-7th December 2025.

An interesting week for comparison because I wasn't well, and missed 3 days of training on Monday, Wednesday and Thursday.

I kept to the weekly fasting protocol including the 48 hr fast Sunday night to Tuesday night, but my refeed choices dramatically impact next-day scale numbers.

All weights are morning numbers

You can see the spikes in weight gain on the Thursday morning and the Saturday morning following food intake choices.

Weeks 5-6

Date range: 15th-28th December 2025.

The image below shows how my weight fluctuations between fasts and refeeds across weeks 5-6 of the experiment. Now recovered from illness, I was fasting and training on the days I missed in week 3. But you can see that the 2 weeks look very different.

Week 5 from Wednesday to Friday has fluctuations within half a kilogram. Fitness was strong and nutritional intake was sufficient for my needs.

But on Friday 19th December, I had 6 pints in the evening which bumped my weight by almost 1.5kg on the Saturday morning. With no hockey on the Saturday to utilise the glycogen and dispel the water, weight is up again by 0.5kg from glycogen intake on the Saturday.

A fast from Saturday to Sunday allowed water release and a 0.3kg drop, which then continued down into the 48hr fast Sunday night to Tuesday night - and actually on into the Wednesday too.

Where week 5 was relatively steady Wednesday-Friday, week 6 is very different. The Wednesday marked at 75.5kg is Christmas Eve. I ran in the morning ahead of Christmas Day on the Thursday - and the weight increases thereafter speak for themselves. But it's all water.

All weights are morning numbers

Contrasting Scale Data

Week 19-20

Date range: 28th March - 5th April 2026.

During my transition from the combined fasting, cardio and light strength sessions; to fasting, cardio, more strength sessions and advances in weight, to build muscle, my body has adapted and changed how it reacts to nutritional intake. And ultimately, the scale weight the morning after.

All weights are morning numbers

The spike at the first weekend is caused by refined sugar foods, specifically my new nemesis - birthday cake! (Look out for an upcoming blog on Why Sugar Crashes Changed After 12 Weeks of Fasting).

What this graph doesn't show is my upgraded fitness programme and intake needs in week 20. At this point I'm training 6 days a week as standard (although in this particular week, only 4 due to life circumastances).

My lift strength and frequency is up, and as such, so is my intake!

In contrast to the earlier weeks I've shared, my intake here is significantly up - but my weight gain is not. Weight increases shown are still water retention, but my body needs the increased nutritional intake to repair muscle and fully top up depleted glycogen from increased training.

For additional reading, check out this blog on why performance can improve without constant eating.

The morning scales aren't just affected by the food you eat, but by a common additive - salt.

Sodium, Timing, and the Illusion of “Gaining Weight”

Salt and pepper makes every meal taste better. For me, that was especially true on a vegan, whole plant-based food diet.

Something I have found, is that sodium intake, especially when timed around training, also influences short-term water retention.

A higher-sodium meal post-training can:

Improve recovery
Restore fluid balance
Increase temporary water retention

On the scale, this looks like weight gain, but in reality, it’s part of the recovery process.

Timing plays a role too.

A late refeed means:

Food still in the digestive system
Fluids not yet processed
Glycogen still being stored overnight

So the next morning’s weigh-in captures all of it. Take a look at Why Weeing at 2-3am Can be a Good Thing

The Pattern Most People Miss

Here’s where it gets interesting.

The weight spike is not random.

It follows a pattern:

Fast → weight drops
Refeed → weight jumps
24–48 hours later → weight stabilises or drops again

And often:

Performance improves in the window after the refeed. I've seen this first hand in weight sessions the morning after a refeed the previous evening. For example, on the Bent-over Barbell Row my lifts have increased progressively from 3 sets of 10 reps on 15kg back on the 26th December 2025, to 2 sets of 15 reps + 1 set of 20 reps on 20kg in April. (These are part of wider super-sets, as opposed to isolated lifts).

This is the key shift.

The scale is not showing fat gain. It’s showing fuel availability.

Critically, once the protocol moves from fat loss to muscle gain, it's less about scale weight anyway, and other measurements become more important. By the time you progress to Week 20, you'll have learnt how your body responds to food and what scale weight really means for you - and how it's different to what it meant in Week 1.

Where People Go Wrong

The mistake isn’t the refeed.

It’s the reaction to the scale.

People see the spike and:

Cut food too aggressively
Remove carbs
Extend fasting unnecessarily

Which leads to:

Poor recovery
Lower performance
Increased hunger later
Disrupted sleep

The system breaks, not because of the refeed, but because of the misinterpretation.

What to Look At Instead

If you want a clearer signal, zoom out.

Don’t judge the system on a single weigh-in.

Look at:

3–5 day trends
Waist measurements
Performance output
Hunger signals

This is where the truth sits. Not in a single number the morning after you eat.

For reference, check out this Podcast episode by Dr Stephen Cabral on How to Reduce Water Retention and Puffiness.

The Real Reframe

A post-refeed weight increase is not a problem.

It’s a checkpoint.

It tells you:

Glycogen is being restored
Recovery is happening
The system is active

The mistake is expecting the scale to move in a straight line.

It doesn’t.

Not when you’re training.
Not when you’re fasting.
Not when you’re doing both.

Final Thought

If you’re combining structured fasting with performance training (regardles of your diets choice), you have to accept this:

The scale will lie to you in the short term.

But if you understand what it’s actually showing, it becomes one of the most useful signals you have.

Not a measure of failure.

But a marker of what your body is doing next.

Frequently Asked Questions

Is weight gain after eating normal?
Yes. Most short-term increases are water, glycogen, and food volume, not fat.

How long does refeed weight last?
Typically 24–48 hours, depending on activity, hydration, and intake.

Do plant-based diets cause more water retention?
They can temporarily, due to higher carbohydrate intake, but this supports performance and recovery.

Should I ignore the scale after a refeed?
Not ignore — but interpret it correctly. Look at trends, not single readings.

Photo by i yunmai on Unsplash

Why Weeing at 2–3am Can Be a Good Thing

Chris Dunkerley — Sun, 05 Apr 2026 22:27:27 GMT

Waking up at 2–3am needing to pee is usually seen as a problem.

Social media likes to push products and treatment to solve weeing at 3am, and from a performance perspective, interrupted sleep can lead to broken recovery if you don't get back off quickly.

But during structured intermittent fasting and training, the body builds on and enforces a natural process to support the system - a pattern validated by the data I've recorded since November 2025.

Key Insights

• Waking at 2–3am to urinate during fasting can reflect glycogen depletion and water loss
• Night urination during fasting is often linked to fluid shifts, not just hydration timing
• It can align with short-term drops in body weight and a leaner morning look
• Not all night waking is positive. Context and patterns matter more than one-off events
• Understanding these signals is key to separating fat loss progress from noise

What I Noticed

Across multiple weeks of structured intermittent fasting, combining longer fasting windows of 48hrs+ with other windows both beyond 20:4 and within 16:8, a clear pattern started to show up.

On certain nights, I would wake up around 2–3am needing to urinate.

On closer inspection, the pattern specifically aligns with evenings where I am fasting, and have stopped eating well before 10pm. When eating stops later, this pattern is much less consistent.

The interesting part was what followed the next day.

Additional urination circa 7am despite no water intake overnight
Body weight would often drop
Midsection felt flatter
Morning look was noticeably leaner
No negative impact on performance

This was happening within a whole-food, plant-based approach, where carbohydrate intake is naturally higher and glycogen storage plays a bigger role in day-to-day energy.

It became clear this was not just about drinking too much water late at night. Something else was happening.

What’s Actually Going On

As a reminder - all the food we eat, is converted into glycogen to be used (and stored for later), in our body... although as per Dr Peter Attia's work on nutrition and glycogen storage, the ability of our body to store glycogen from carbohydrate is limited. What isn't either used immediately, or able to be stored as glycogen, is stored as fat in the form of triglycerides.

In a fasted state, stored glycogen is used to fuel the body whether you're walking to the shops, or training for fitness. When you extend fasting windows, your body shifts how it stores and uses energy. This is amplified when you layer in performance training for cardio and strength.

Glycogen stores reduce. Insulin levels drop. Fat mobilisation increases.

And with that utilisation of glycogen, water moves.

For every gram of glycogen stored, your body holds roughly 3 grams of water.

As glycogen is used, that water is released.

It has to go somewhere.

Often, that shows up as increased urination during sleep.

In a vegan fitness setup, where meals are typically higher in whole-food carbohydrates like rice, oats, and legumes, glycogen storage and release becomes even more visible through these fluid shifts.

This article from Dr Peter Attia on the interplay of ketosis and exercise, reveals more about water release from glycogen use as a bi-product of training.

This relationship between glycogen depletion and water loss is well established in metabolic research and is often observed in early-stage weight changes during fasting.

Why It Happens at 2–3am

At night, your body is already in a natural fasting state.

Add structured intermittent fasting on top of that, and the signal becomes stronger. Layer performance training on top of intermittent fasting, and the effect is magnified.

Hormonal changes during sleep support this shift. Lower insulin levels, increased fat utilisation, and fluid regulation all combine.

So instead of holding onto water, your body starts releasing it.

And once you establish a fasting rhythm (even before establishing a fitness pattern), your body will wake you up to do exactly that.

Why Night Urination Can Be a Good Sign

In this context, waking to urinate at night is not just an inconvenience.

It can be a signal that:

• Glycogen depletion is progressing
• Water retention is reducing
• Your body is shifting fuel sources effectively
• The fasting window is doing its job
• This can be more noticeable in plant-based athletes due to higher glycogen turnover

This is especially true when it is followed by a leaner look and a drop in scale weight the next morning.

To give you an indicator, the data I've tracked (at the time of writing, 20 weeks: 16th November 2025-5th April 2026) shows my body will flush up to 3kg of water retention over a 48hr fast. But it's important to frame this in the context of refuelling and maintaining a glycogen rich system to support fitness performance. Fluctuation in your scale weight after a refeed is not fat - nor permanent weight gain.

Where People Get It Wrong

Not every 2am wake up is a positive signal. If sleep quality is consistently disrupted, this becomes a recovery issue rather than a useful signal.

Night urination can also be caused by:

• Drinking large amounts of water late at night
• Caffeine intake
• Electrolyte imbalance
• Disrupted sleep patterns

If it is paired with:

• Poor sleep quality
• Persistent fatigue
• Dizziness or cramping

Then it is likely a problem, not progress. These are red flags when fasting and exercising whether you're on a vegan diet or not.

What Changed for Me

Instead of seeing these wake ups as disruption, I started properly assessing the data around them, and looked at what happened before and after.

• What did I eat before the fast?
• How long was the fasting window?
• What was training load like?
• What happened to weight and performance the next day?

I'm ever grateful that I started tracking the numbers around my experience and wider experiment, and I encourage you to do the same. It's impossible to assess your progression without capturing the moments that make up your day to day, to allow you to look back and assess patterns that you can't see when you're in the moment.

I'm still unlocking patterns, and their meanings.

The Bigger Lesson

This is one of the easiest signals to misinterpret.

Most people optimise for comfort. But not all discomfort is a problem. Sometimes it's feedback.

Structured intermittent fasting is not just about duration. It is about understanding what your body is telling you as variables change.

This became even more relevant within a plant-based performance approach, where fuel storage, fluid balance, and recovery all interact more dynamically.

Key Takeaways

• Waking at 2–3am to urinate during fasting is not always negative
• It can reflect glycogen depletion and fluid release
• It may align with short-term weight loss signals
• Patterns matter more than isolated events
• Interpreting signals correctly improves decision making

FAQs

Is waking up to wee at night always a sign of fat loss?

No. Night urination can result from hydration, caffeine, or sleep disruption. In fasting, it can reflect fluid shifts, but only patterns over time make it meaningful.

Does intermittent fasting cause more night urination?

It can. As glycogen stores deplete and water is released, the body may excrete more fluid, including during sleep.

Should I reduce water intake before bed?

Not automatically. Hydration should support performance and recovery. This is about observation, not restriction.

Final Thought

The process became clearer when I stopped reacting to single events.

And started paying attention to patterns.

Because sometimes, the things that feel like problems, are actually signs that something is working.

If you’re experimenting with fasting and training, this is one of the simplest signals to start paying attention to.

Photo by Evan Marvell on Unsplash

Why Nutrition Needs Change When Fasting: Strength vs Fat Loss Explained

Chris Dunkerley — Tue, 24 Mar 2026 19:42:19 GMT

Over the past few months, I’ve been running a structured experiment combining plant-based nutrition, intermittent fasting, and regular training.

For a long time, the system worked exactly as expected. Weight was stable. Energy was consistent. Performance was improving.

Then in week 18, that changed.

Despite following the same fasting structure and eating the same types of foods, true hunger started showing up far earlier, both during the day and in the night.

Nothing had “failed”. But something had clearly shifted.

That week exposed a simple truth that most fasting advice overlooks.

Fasting works.
But the nutrition inside it has to change depending on what you’re asking your body to do.

Key Insights

Fasting does not fail, but nutrition inside it must adapt to your goal
Fat loss and performance require different fuelling strategies
Glycogen availability is a key driver of performance and recovery
Plant-based diets require more deliberate structuring during higher training phases
Appetite increases are often a recovery signal, not a discipline issue
Waking at night, performance dips, and persistent hunger are signs of under-fuelling
Longer or more flexible eating windows may be required after extended fasts

You cannot train at a high level on a fat loss fuelling strategy indefinitely.

The Real Issue: When Demand Changes, the System Must Too

When you fast for fat loss, the goal is controlled energy use. You are deliberately running the system slightly under-fuelled to encourage fat utilisation.

When you switch it to align with strength or performance, the goal changes completely. Now the body needs to perform, recover, and adapt.

The mistake is trying to use the same nutrition approach for both.

What worked perfectly for fat loss can quietly become under-fuelling when training intensity increases.

Fat Loss vs Performance: What I Found Actually Changes

What became clear is that the system itself wasn’t wrong. It was just no longer aligned to the demand being placed on it.

Variable	Fat Loss Focus	Strength / Performance Focus
Glycogen demand	Controlled depletion	Active replenishment
Appetite signals	Stable or suppressed	Increased and reactive
Recovery requirement	Lower	Significantly higher
Meal density	Moderate	Higher
Eating window	Tighter	Often needs extending

Once I moved to heightened strength and performance sessions, progressing lift capability and cardio times, my body passed a turning point. It started to tell me that more fuel was needed, and this time, I listened.

Come to think of it, the same thing happened right back at Week 0. It's what led me to start this experiment. But this was a monster change that surprised me at Week 18.

Critically. During Weeks 13-17 I adapted fully, to being able to recognise true hunger vs habit hunger. This stability really helped me to understand that what I needed was genuine, and not about eating more for the sake of it.

Instead, it was all about balancing intake with output.

The Glycogen Factor Most People Miss

Glycogen is the body’s stored form of carbohydrate. It is the primary fuel for higher intensity training.

In a fat loss phase, running glycogen lower can work well. Energy remains stable, and fat utilisation increases.

But in a performance phase, glycogen becomes critical.

If it is not replenished properly, performance drops, and intake can start to spiral if the body doesn’t feel fuelled at the right times.

This is where I got caught out.

Some of my best runs have happened over 20 hours into a fast. But those only worked because glycogen had been properly restored ahead of time.

When it wasn’t, the difference was obvious.

Equally, when I failed to refeed with correct meal structure; generally due to life or simply missing ingredients, my body kept calling for food, despite having taken ample.

Why This Can Catch Plant-Based (Vegan) Diets Out

Replenishing glycogen is not harder on a plant-based diet. But it does require more deliberate food selection.

Whole-food plant-based diets tend to be:

High in fibre
High in volume
Slower to digest
Lower in calorie density per bite

This works perfectly in a fat loss phase.

But in a performance phase, it can create a hidden problem.

You feel full before you are fully fuelled.

Endurance coach Matt Frazier, founder of No Meat Athlete, has long highlighted that plant-based diets can fully support athletic performance when they are structured appropriately for the demands being placed on the body.

Similarly, former professional triathlete Brendan Brazier has written extensively about how plant-based nutrition supports performance and recovery, particularly when energy intake aligns with training load.

The key is not just eating clean. It is eating in line with demand, and the phase you are in.

In my own structure, this meant:

Using easier-digesting carbohydrate sources when needed
Avoiding stacking too many high-fibre foods in one window
Making sure protein remained anchored without crowding out energy intake

High-quality food is not always the same as performance-appropriate food.

Appetite Is Not the Problem

One of the biggest shifts I noticed was appetite.

During fat loss phases, hunger felt controlled and predictable. Once you nail the refeed window and strategies to avoid over-eating, everything becomes routine.

During higher training weeks, appetite increased noticeably. Even on days where total activity had not changed dramatically.

It’s easy to misinterpret this as a lack of discipline, or even fasting failure.

In reality, it is a recovery signal.

Ignoring it is where problems start.

Recovery Does Not Always Show Up Immediately

Another key insight from this phase was delayed demand.

After a long fast, there isn’t a great deal of time in an evening eating window to fully replenish the glycogen in your system.

I found that my body would feel full for a while, but secondary signals for top-up would come hours later.

In my case, it showed up as waking at 2am hungry, despite having eaten earlier in the evening.

That is not random.

That is the body asking for what it did not get during the eating window.

After a 20 to 48 hour fast, the body is not just looking for food. It is looking for restoration.

Trying to compress that into a very tight eating window can work for fat loss.

It becomes much harder when performance and recovery are the priority.

What worked best in my structure was:

Allowing time between food intake rather than rushing everything in
Avoiding stacking large amounts of carbohydrates all at once
Keeping protein consistent across the window
Accepting that some days required a slightly longer eating period to fully recover

This is not about abandoning structure.

It is about adapting it.

Warning Signs You Are Under-Fuelled

These signs are easy to ignore, especially when the overall system feels disciplined.

Waking up hungry during the night
Persistent stomach growling despite eating
Drop in training performance
Flat or heavy feeling during sessions
Low motivation or irritability

These are not discipline issues.

They are fuel issues.

What My Data Showed

During earlier weeks focused on fat loss, intake remained relatively controlled and results were consistent.

As training intensity increased, the same intake patterns no longer matched demand.

In one specific week, despite maintaining structure:

Hunger increased
Sleep was disrupted
Performance dipped slightly

Weight and waist measurements alone did not tell the full story.

The signals did.

That was the moment it became clear that the system needed to evolve.

The Takeaway

Fasting is not a fixed system.

It is a structure that needs to adapt based on the goal.

Fat loss and performance are not the same phase, so should not be fuelled the same way.

The shift is simple, but important.

From restriction - to refuelling.

The structure stays.

But the nutrition inside it must evolve.

A Quick Note on Individual Differences

This is a structured personal experiment, not a universal prescription.

Factors like genetics, food tolerance (and choice), training type, fasting schedule, and overall lifestyle, will influence how this applies to you.

Above all, it’s vital that you listen to (and understand) both your body, and the variables.

FAQs

Does fasting affect strength and performance?

Fasting itself does not automatically reduce strength or performance. However, performance can drop if glycogen is not properly replenished during eating windows. The issue is usually under-fuelling, not fasting itself.

Why do I feel more hungry when training while fasting?

Increased hunger during training phases is often a recovery signal. As training demand increases, the body requires more energy and nutrients to repair and adapt.

Can you build strength while fasting on a plant-based diet?

Yes, but it requires careful planning. Protein intake, carbohydrate selection, and total energy intake all need to align with training demand. Plant-based diets can support performance, but food choice and timing become more important.

Why am I waking up hungry at night while fasting?

This is often a sign that your body has not fully recovered from training or that glycogen has not been adequately replenished. It can occur when intake does not match output during the day.

Do I need to eat more when training harder?

Not always more in volume, but more appropriately for the demand. This may include higher carbohydrate availability, better meal spacing, or a slightly longer eating window.

If you have ever felt your performance drop despite doing everything “right”, it may not be the fasting.

It may be that your nutrition has not yet caught up with your training.

What signals does your body give you when your intake doesn’t match your output?

Why Some Foods Suddenly Cause Gas & Digestive Problems After Eating Clean

Chris Dunkerley — Sun, 15 Mar 2026 21:44:00 GMT

Have you started noticing unexpected symptoms after months of eating a simple whole food diet? Foods that used to seem normal suddenly causing gas, bloating or digestive problems? This is not unusual. It is often a sign that your gut microbiome and digestion have adapted to a cleaner and more consistent diet.

Short answer:

This happens because the gut microbiome adapts to the foods you eat most often. When someone eats a simple whole-food diet for long periods, digestion becomes specialised for those foods. Introducing unfamiliar ingredients, processed foods or new fibre sources can temporarily increase fermentation in the colon, which may lead to gas, strong odours or loose stool.

Understanding why this happens requires looking at how digestion adapts to diet over time.

Why Digestive Problems Can Appear After Switching to Clean Eating

When people shift towards a simpler whole-food diet, their digestive system gradually adapts to that pattern of eating.

The gut microbiome is not static. It changes based on what you regularly consume. Different bacteria specialise in digesting different nutrients. If your diet becomes consistent and based on whole foods such as grains, legumes and vegetables, the bacteria that thrive on those foods gradually become dominant.

This often improves digestion overall. Meals are broken down more efficiently. Bowel movements become more regular. Many people notice less bloating and more stable digestion.

However, this adaptation also creates something called digestive specialisation.

When the body becomes accustomed to a narrow range of foods, introducing unfamiliar ingredients can temporarily disrupt that balance. The digestive system has become efficient at handling certain fibres and nutrients, but less adapted to others.

Processed foods, additives and complex mixed meals can therefore produce stronger digestive reactions than they did before.

Why Gas and Fermentation Increase When Diets Suddenly Change

Gas production in the digestive system is mainly caused by fermentation in the colon.

Many carbohydrates and fibres are not fully digested in the stomach or small intestine. Instead, they reach the colon where gut bacteria ferment them. This fermentation process produces gases such as hydrogen and carbon dioxide.

These gases are normal and expected. In fact, fermentation is also responsible for producing beneficial compounds called short chain fatty acids, which support gut health.

However, when diet changes suddenly, fermentation patterns can change too.

Different fibres feed different bacteria. If a person suddenly eats foods containing new types of fibre, resistant starch or processed carbohydrates, the bacteria in the colon may ferment them more aggressively until the microbiome adjusts.

This temporary increase in fermentation can lead to:

more gas
bloating
changes in stool consistency
increased bowel movements

For many people this settles once the microbiome adapts again.

Why Ultra-Processed Foods Can Cause Digestive Reactions After Clean Eating

Ultra-processed foods often contain ingredients that the digestive system rarely encounters during a whole-food diet.

These may include:

emulsifiers
stabilisers
protein isolates
gums
modified starches

These ingredients are used to improve texture, shelf life and flavour. They are not necessarily harmful, but they can behave differently in the digestive system compared with whole foods.

When eaten regularly, the gut microbiome adapts to these ingredients. But when someone has been eating a very clean diet for weeks or months, the microbiome may not be well adapted to processing them.

As a result, these ingredients can sometimes trigger increased fermentation, gas or changes in stool consistency when they suddenly reappear in the diet.

Why Strong Smelling Gas Can Happen After Certain Meals

Not all digestive gas smells the same.

When gut bacteria ferment carbohydrates, the gases produced are usually relatively mild. However, when bacteria ferment proteins or sulphur-containing compounds, the gases produced can smell significantly stronger.

This smell often comes from gases such as hydrogen sulphide.

Certain foods can increase this type of fermentation, including:

legumes
processed protein foods
onions and garlic
sulphur-rich vegetables

Protein fermentation in the colon can produce particularly strong smelling gases. This does not mean something is wrong. It simply reflects the type of nutrients being fermented by gut bacteria.

A Real Example From My Own Experiment

During my own structured nutrition experiment, most meals are very simple and consistent, which also helps explain some of the patterns I described in the post on [why nutrition needs to work differently when fasting for strength versus fat loss]. They typically include foods such as oats, rice, lentils, tofu and vegetables.

Digestion is usually predictable and stable.

However, at the end of Week 17 after hockey on a Saturday, I had a day of more varied foods, including processed plant-based products, snacks and mixed ingredients that were not part of my usual routine.

Later that evening I experienced a short period of very strong gas and loose stool that lasted a couple of hours. The gas was particularly strong smelling, which suggested sulphur-based fermentation. [For context - I've been on a plant-based diet for 7+ years at this point and very rarely struggle with this.]

The next day digestion had completely returned to normal, although my system took another 18 hours to work the fermented gases completely free.

This kind of short-term reaction is consistent with a temporary fermentation response to unfamiliar ingredients rather than a food intolerance or illness.

What made it more interesting was the contrast with normal weeks. This wasn't a case of introducing one unfamiliar ingredient. It was a combination of processed plant-based products, varied snacks and mixed ingredients arriving together, all in a single sitting, after weeks of very consistent and simple eating. The gut wasn't in an unusual state. The food was.

That distinction matters. The same variety of foods eaten in week two of the experiment would likely have passed without incident. By week 17, the microbiome had adapted so specifically to a clean, consistent pattern that the deviation produced a reaction the earlier version of my diet never would have.

During my experiment I also started noticing that digestion, energy levels, and performance were closely linked to how often I ate, not just what I ate. I explored that in more detail in my article on why performance can sometimes improve without eating all the time.

Does This Mean You Should Avoid Those Foods Completely?

Not necessarily.

Occasional digestive reactions do not mean a food is harmful or that it should be permanently avoided.

The digestive system is adaptable. The microbiome changes based on what you eat regularly. If a food appears more frequently in the diet, the gut often becomes better at processing it.

In many cases, digestive reactions simply reflect dietary variability, not intolerance.

It is also worth remembering that meals containing many different ingredients can naturally produce more fermentation than simple meals.

The key is to recognise that occasional digestive responses are normal and usually temporary.

Why Do Healthy Foods Sometimes Cause Gas?

Many healthy foods contain large amounts of fibre and complex carbohydrates that the body cannot fully digest.

Instead of being absorbed in the small intestine, these compounds travel to the colon where gut bacteria ferment them.

Foods commonly associated with gas include:

beans and lentils
whole grains
certain vegetables
high-fibre plant foods

While this fermentation produces gas, it also produces beneficial short chain fatty acids that support gut health and metabolic function.

In other words, gas from healthy foods is often a normal by-product of a functioning microbiome.

How Digestive Sensitivity Evolved Across 20 Weeks of Plant-Based Fasting

One thing that general gut health advice rarely covers is how this kind of sensitivity changes over a long-running experiment.

In the earlier weeks, my digestion was fairly robust to dietary variation. Processed plant-based foods at weekends produced no notable reaction. That began to shift somewhere around weeks 10 to 12.

By that point the weekday diet had become genuinely tight and consistent. The microbiome had adapted to a narrow, predictable range of foods. And the result was that when deviation happened, my body noticed it more, not less. The cleaner the baseline, the more pronounced the contrast.

By Week 17 the difference was stark enough to produce the reaction I described above. Foods I had eaten without issue for years triggered something I hadn't experienced in a long time.

This isn't a problem. It's a signal that adaptation is working. But it does suggest that digestive sensitivity isn't static over the course of a long experiment.

It evolves alongside the diet. And if you're combining a consistent whole-food plant-based approach with structured fasting, that evolution may be faster and more pronounced than it would be with diet alone.

The Real Lesson: Consistency Makes Digestion Predictable

One clear pattern that has emerged from my nutrition experiment is that simple, consistent meals produce the most predictable digestion.

Whole foods such as grains, legumes and vegetables provide fibre and nutrients that the microbiome can adapt to over time. When meals follow a consistent pattern, fermentation becomes more stable and digestion often feels smoother.

In contrast, meals containing many processed ingredients, additives or unfamiliar foods can temporarily disrupt that balance.

This does not mean those foods must be avoided. It simply highlights how strongly the digestive system responds to consistency.

Understanding this relationship can help explain why digestive reactions sometimes appear after switching to a cleaner diet.

What I'm Still Watching

There are a few things from this I haven't been able to answer yet.

The first is whether this sensitivity plateaus. At 20 weeks, a significant dietary deviation still produces a clear response, (the most recent of which to emerge is the effect of refined sugars, which I'll do a blog on). Whether that remains true over a full year, or whether the gut eventually develops a wider tolerance, I don't know.

The second is refeed timing within the fasting cycle. My instinct is that what you eat immediately after an extended fast matters more than what you eat at other points in the week. If that's true, it has real implications for how people structure their first meal back, (in line with safety protocols), and consequent meal structure in the days that follow. Most fasting guidance doesn't address this at all. I'm paying closer attention to it now.

The third is water volume. On days when my water intake is at its highest, any digestive disruption seems to move through faster. That might be incidental. It might reflect how hydration supports gut motility. Not enough data to claim anything yet. Just a pattern I keep noticing.

Key Takeaways

The gut microbiome adapts to the foods you eat regularly.
Switching to a consistent whole-food diet can make digestion more specialised.
Sudden dietary changes can increase fermentation in the colon.
Ultra-processed foods and unfamiliar ingredients may trigger temporary digestive reactions.
Strong smelling gas often results from sulphur compounds produced during protein fermentation.
Simple and consistent meals tend to produce the most predictable digestion.

Frequently Asked Questions

Why do I get gas after switching to a healthier diet?

Gas often increases when people switch to a healthier diet because many whole foods contain more fibre. Fibre is fermented by gut bacteria in the colon, producing gas as a natural by-product. As the gut microbiome adapts to the new diet, this usually settles.

As gastroenterologist Dr Will Bulsiewicz explains, increased fibre intake feeds beneficial gut bacteria. During this process those microbes ferment fibres and produce gas as a natural by-product. For people transitioning to a high-fibre plant-based diet, temporary bloating or gas can simply be a sign that the microbiome is adapting.

Can eating clean make your digestion more sensitive?

In some cases, yes. When someone eats a simple and consistent whole-food diet for a long period, the gut microbiome adapts to those foods. Introducing unfamiliar ingredients or processed foods can temporarily disrupt that balance and increase fermentation.

Why do some foods suddenly cause digestive problems?

Digestive reactions can occur when the body encounters foods it has not been eating regularly. The gut microbiome adapts to common foods over time. When new fibres, additives or ingredients appear, fermentation patterns may temporarily change.

Why does gas sometimes smell so strong?

Strong smelling gas often comes from sulphur compounds produced when gut bacteria ferment proteins or sulphur-containing foods. Foods such as legumes, onions, garlic and some processed protein products can increase this type of fermentation.

Does gas from healthy foods mean something is wrong?

No. Gas is a normal result of fermentation in the colon and is often a sign that fibre is feeding beneficial gut bacteria. However, sudden changes in diet can temporarily increase gas production until the microbiome adapts.

Why Even Experienced Fasters Struggle When They Start Training Hard

Chris Dunkerley — Fri, 13 Mar 2026 22:29:21 GMT

When I started this experiment I had already been fasting for several years. Completing a 48 hour fast was not unusual for me, and my appetite signals were generally stable. Hunger felt predictable and energy levels were reliable.

Because of that, I assumed adding structured training would be fairly straightforward. Running sessions, strength work and hockey on top of the fasting routine seemed like a logical next step.

What I did not expect was how much those new variables would change the way hunger and recovery signals behaved.

The fasting itself was not the challenge. Learning how training interacted with it was.

You can comfortably complete a 24 or 48 hour fast. Your appetite feels stable. Energy is steady. Hunger is predictable.

Then something changes.

You add structured training.

Running sessions. Strength work. Team sport. Higher intensity movement.

Suddenly things feel different again.

Hunger appears at unusual times. Sleep can be disrupted after late refeeds. Appetite signals feel less predictable. Recovery sometimes feels delayed.

For many people this feels confusing.

But the reality is simple.

Combining fasting with serious training introduces an entirely new learning curve.

Key Insights

Even experienced fasters can struggle when they begin integrating serious training into their routine. Training introduces new recovery demands such as glycogen depletion, muscle repair and electrolyte loss, which can shift when hunger signals appear. Appetite may surface hours later or even the following day as the body restores energy and repairs tissue. Structured refeeds and consistent meal sequencing help stabilise these signals while the body adapts. Over time, fasting and training together become a skill that improves with experience and observation.

Fasting experience does not automatically translate to training recovery

What surprised me most during the experiment is that previous fasting experience did not automatically translate into smooth training recovery.

I had been completing extended fasts for years without difficulty. Appetite was controlled and eating windows felt well established.

But once structured training became part of the week, new patterns began to appear in the data.

Hunger sometimes arrived much later than expected. Recovery appetite occasionally showed up the following evening rather than immediately after a session. Even sleep quality could change depending on how a refeed was structured.

None of these signals had appeared when fasting alone.

They only emerged once training entered the equation.

The reason is that fasting and performance place very different demands on the body.

Fasting teaches your body to operate with lower insulin levels, increased fat oxidation and stable appetite rhythms.

Training introduces new variables.

Muscle damage. Glycogen depletion. Nervous system fatigue. Electrolyte loss.

These variables change how and when your body signals hunger.

Many experienced fasters expect their hunger signals to behave exactly the same as before. When they do not, they assume something is wrong - I certainly did!

In reality, the body is simply adapting to a new set of demands.

The delayed recovery hunger effect

One of the most surprising things I observed during my own structured fasting experiment is that hunger often appears long after the training session itself.

It does not always show up immediately after exercise.

Sometimes it arrives the following evening.

During week 17 of the experiment, a fasted Thursday evening run created a recovery demand that only appeared fully the following night. Appetite signals were noticeably stronger than usual, and extending the refeed across multiple pauses disrupted sleep. Condensing the refeed into a shorter window solved the issue immediately.

That was a useful reminder that recovery signals sometimes appear later than expected when training is combined with fasting.

At first glance this seems strange.

But physiologically it makes sense.

During a fasted run the body is working with limited glycogen availability. After the session it begins repairing muscle tissue and restoring energy stores. These processes continue for many hours.

If the initial refeed is late in the evening, recovery can extend well into the following day.

The appetite signal that appears later is not random hunger. It is the body completing the recovery process.

Why structure matters when training while fasting

Early in my experiment I followed a very consistent feeding structure.

Meals were separated by deliberate pauses to allow digestion and appetite signals to stabilise.

This worked extremely well on most days.

However, after particularly demanding training sessions, something interesting happened.

If the refeed was stretched out over several hours late in the evening, sleep could sometimes be disrupted.

The digestive system was still active. Recovery demand was still high. Appetite signals could reappear during the night.

Eventually I realised that certain training days required a slightly different feeding structure.

Instead of spacing meals with long pauses, the recovery meal could be condensed into a shorter window. This allowed the body to complete digestion earlier and improved sleep quality.

This adjustment was not about eating more food. It was about understanding when recovery demand was genuine.

Structured fasting is a skill

One lesson that has become clear over time is that recognising these signals takes practice.

Earlier in the experiment I followed my feeding structure quite strictly. Meals were spaced with deliberate pauses so that digestion and appetite signals had time to settle.

That structure worked well, but there were moments when recovery demand was clearly higher than usual. On those days the body signalled genuine hunger more strongly and more quickly.

At first it was difficult to distinguish whether that hunger was habit, digestion or recovery.

Over time, by tracking training sessions, refeeds and sleep patterns, the signals became much easier to recognise.

What initially felt confusing eventually started to make physiological sense.

In reality it takes time.

Even experienced fasters go through a learning process when they introduce serious training.

At first the safest approach is structure.

Consistent eating windows. Predictable refeeds. Clear meal sequencing.

Over time hunger signals become easier to recognise.

Recovery appetite becomes distinguishable from habit hunger.

Eventually the system becomes flexible rather than rigid.

At that point the protocol is no longer something you simply follow. It becomes something you understand.

This approach is not designed for beginners

It is important to say this clearly.

The kind of structured fasting described here is not intended for people new to fasting.

It works best for individuals who already have experience with longer fasting windows and stable appetite control.

When fasting and training are combined correctly the body can become extremely efficient at managing energy and recovery.

But it requires patience, observation and a willingness to learn from real signals rather than forcing rigid rules.

Final thought

If you have experience with fasting and you have recently introduced serious training, you may have noticed that appetite behaves differently.

That does not mean the system is failing.

It may simply mean your body is adapting to a new level of demand.

The key is learning to recognise when hunger is simply habit, and when it is the body asking for recovery.

I would be curious to hear your experience.

If you regularly practise intermittent fasting and train seriously, have you noticed your hunger signals changing as training intensity increases?

Frequently asked questions about fasting and training

Can you train hard while fasting?

Yes, many experienced fasters can train effectively while fasted. However, training introduces additional recovery demands such as glycogen restoration, muscle repair and electrolyte balance. This is why structured refeeds and proper hydration become more important when fasting and training are combined.

Why do I feel hungry long after my workout when fasting?

Hunger does not always appear immediately after exercise. When training while fasted, the body may continue repairing tissue and restoring glycogen stores for many hours. This can create delayed hunger signals later in the day or even the following evening. Food choices within your refeed window are also critical to get the right kind of energy for your body (physiology).

Is fasting and training suitable for beginners?

Combining extended fasting with structured training is generally better suited to people who already have experience with fasting. Beginners often benefit from stabilising their fasting routine before adding intense training.

*Photo by Stavros Papadimitriou on Unsplash

Why Performance Can Improve Without Eating All The Time

Chris Dunkerley — Mon, 09 Mar 2026 20:11:50 GMT

The default assumption in sport is simple.

If you want to perform well, you need to eat regularly.

Athletes are often encouraged to fuel constantly. Breakfast, snacks, recovery drinks, energy gels and carbohydrate loading all reinforce the same message. Energy in, must match energy out.

For many people, that advice works.

But what happens when the body becomes properly adapted to fasting?

Key insight

Performance does not always require constant feeding. When the body becomes metabolically flexible through structured fasting and training, it can draw more efficiently on stored energy. This may improve endurance stability, respiratory efficiency and recovery between efforts.

Over the past several months (since November 2025), I have been running a structured fasting experiment combining intermittent fasting, plant-based nutrition and consistent training. What began as a curiosity around advancing my metabolic adaptation, has gradually turned into something far more interesting.

Not only has performance improved, but in several areas it has improved while training inside fasting windows.

That outcome initially surprised me.

The Assumption Most People Start With

When people first hear about exercising while fasting, the reaction is usually the same.

Energy will crash.
Muscle will be lost.
Training quality will drop.

At a glance those concerns appear logical. If food is the primary fuel source for physical activity, then removing food should reduce performance.

Yet the human body is more adaptable than that.

The metabolic system is not designed to rely on one fuel source alone. It constantly shifts between stored glycogen, circulating glucose and stored body fat depending on availability and demand. (This is not something I knew when I started this experiment, but something I learned along the way).

The question is not whether the body can do this.

But how efficiently can it switch between those systems?

Early Adaptation Versus Deeper Adaptation

Many people experimenting with intermittent fasting are familiar with the early stages of fat adaptation.

Around eleven hours into a fasting window the body typically begins shifting towards increased fat oxidation. For people new to fasting this is often where the noticeable benefits appear. Mental clarity improves, appetite settles and energy levels become more stable.

For most casual fasters operating in an around the 16:8 (off:on) eating windows, this is where the exploration ends and the process repeats.

But extending that process further while maintaining consistent training appears to reveal additional adaptations.

For me, I have seen and recorded;

Improvements in respiratory efficiency.
Improvements in energy stability.
Advancements in cardio and strength performance.
Faster recovery between efforts.

These changes do not arrive overnight. They emerge gradually through repetition.

Observations From The Current Experiment

During the early stages of this experiment I expected some compromise in performance during fasted training. And in fact, my performance had already plateaued before starting.

However, once I corrected the errors and established a better structure, the opposite began to appear.

Fasted runs became progressively easier to sustain. Breathing settled more quickly during difficult sections of a route. Recovery between hockey sprints improved.

Strength training also continued to progress despite regularly lifting in extended fasting windows (48hrs off) and separately, up to 6-7hrs before eating.

Recently that progress became visible in a very clear way.

A long standing benchmark route of 5.7 kilometres that had resisted improvement for months was finally broken (today 9th March 2026). The run dropped to 26:16, smashing the twenty seven minute barrier and established several new personal bests across different segments of the route. (Data tracked on Strava.

This was not achieved during a heavily fuelled training session, but at 10 hours into a 48 hour fasting window.

At the same time, other changes have appeared.

Breathing during exercise feels more controlled.
Recovery between sprints has improved.
Even my inhaler use has quietly disappeared from my routine. (I don’t know for sure what single component of my routine has led to this, but it aligns with a combination of intake optimisations and sodium management changes).

None of this was expected at the beginning of the experiment.

A Possible Metabolic Explanation

The purpose of this experiment is observation rather than clinical proof, but several physiological explanations appear plausible.

When the body becomes accustomed to switching between glycogen and fat as fuel sources, energy availability becomes more stable. Instead of relying heavily on incoming food, the body learns to draw more effectively from stored energy.

That flexibility appears to reduce the dramatic peaks and troughs that some athletes experience when fuelling constantly.

At the same time, endurance systems appear to benefit from repeated exposure to lower glycogen environments. The body gradually improves its ability to preserve glycogen while drawing additional energy from fat oxidation.

Over time this may support more stable output across longer efforts.

These are not new ideas in sports physiology, but they are rarely explored within the context of plant-based nutrition and structured fasting routines.

The Guardrails Matter

It is important to emphasise that none of these improvements are occurring in isolation.

Training structure matters.
Food quality matters.
Recovery matters.

Fasting alone is not responsible for improved performance. The combination of disciplined eating, thoughtful meal timing and consistent training appears to be what allows the body to adapt - it’s certainly what my data shows.

Within the experiment there are also specific guardrails that support performance. These include careful attention to refeeding meals, sodium intake and the timing (and type) of carbohydrate replenishment around higher intensity sessions.

The details of that framework is what makes up the base of my writing in the book Beyond 20:4 (in progress).

Performance Without Constant Feeding

One of the more interesting realisations from this process is that frequent eating is not always the same thing as effective fuelling.

For some athletes, constant snacking may simply prevent the body from fully adapting to its own internal energy reserves.

When the body becomes confident drawing from those reserves, the need for constant feeding appears to reduce.

That does not mean food becomes less important. Far from it.

It simply means that when food does arrive, it can be structured more deliberately to support training, recovery and metabolic flexibility.

A Shift in Perspective

For years the common narrative around fasting has focused on weight loss.

Yet what this experiment is gradually revealing is something slightly different.

When structured carefully, fasting can coexist with improving physical performance - and the real insight and key component for me, is that I can do it on a clean, whole plant-based diet. Not something people typically write about.

The key to unlocking success, appears to be consistency and patience.

Frustratingly, metabolic adaptation and training progression both take time. Visible results often arrive long after the underlying physiological changes have already begun.

This experiment continues to explore what happens when those processes are allowed to develop together.

*Photo by engin akyurt on Unsplash

The Psychology of Stubborn Fat in Structured Fasting

Chris Dunkerley — Sun, 08 Mar 2026 08:51:32 GMT

One of the most frustrating moments in structured fasting is when progress slows down.

You may be training consistently.
Eating clean food.
Maintaining disciplined fasting windows.

And yet the scale stops moving, or stubborn areas of body fat appear unchanged.

At this point many people assume the system has stopped working.

In reality, the issue is often psychological rather than physiological.

Weight fluctuates day to day. Some mornings it drops, other mornings it climbs. At times it feels as though it's moving in the opposite direction to the effort you are putting in.

If you exercise regularly, the confusion can become even greater. Training sessions feel stronger. Recovery improves. Physical performance advances. Yet the number on the scale refuses to behave in a neat downward line.

This is the point where self doubt begins to creep in.

I have experienced this repeatedly during the current experiment combining advanced intermittent fasting with a plant based diet and structured exercise. Some weeks progress is obvious. Other weeks it feels like the system has stalled entirely.

The truth is usually somewhere in between.

The scale, despite how commonly it is relied upon, is one of the least reliable indicators of real progress when fasting and training are combined.

Why Body Weight Fluctuates

Body weight fluctuates for many reasons that have nothing to do with fat loss.

Water retention shifts depending on salt intake and carbohydrate levels. Glycogen stores expand and contract based on how much fuel has been consumed around exercise. Food volume itself can change scale readings depending on how recently a meal was eaten.

Even inflammation from hard training sessions can temporarily increase body weight while the body repairs itself.

When all of these variables are present at the same time, daily scale readings can become a very misleading signal.

This is particularly noticeable during periods of disciplined fasting.

Fasting windows reduce food volume and glycogen levels, which often leads to sharp early drops in weight. But as training increases and structured refeeds are introduced, glycogen stores return and water levels stabilise. The scale can then appear to plateau, even though body composition is still slowly improving.

The stubborn belly fat problem adds another layer of frustration.

Stubborn Belly Fat

When people refer to "stubborn fat", they are often reacting to this exact phase.

Fat loss is rarely linear when fasting and training are combined. Glycogen storage, hydration levels and inflammation from training can temporarily mask progress that is still occurring beneath the surface.

For me, definition has started to appear in other areas of the body before my abdominal region has seen significant change. Legs and shoulders for example have started to become more defined. And my ribs have started to show slightly through the chest at the side.

Yet the lower stomach remains.

This is the stage where many people begin questioning their approach - I certainly did. The temptation is to make adjustments quickly. Change the fasting schedule. Reduce carbohydrates further. Add extra exercise sessions.

Often the real issue is not the system itself. But the impatience that arrives when visible progress slows down.

One of the most valuable lessons from my own experiment has been recognising how important patience becomes during this phase. Fat loss rarely happens in a perfectly predictable way, especially when exercise performance is also being developed at the same time.

Small improvements accumulate quietly in the background before becoming obvious.

This is one of the reasons I track several variables rather than relying solely on scale weight. Training performance, waist measurements, sleep patterns and food timing all provide useful signals when viewed together.

On several occasions the scale has appeared stagnant while strength has improved and running performance has advanced. That combination tells a much more meaningful story than a single number recorded in the morning.

Patience is a Virtue

The psychological side of this process should not be underestimated.

When discipline is high and effort is consistent, the expectation of rapid results can become strong. When those results do not appear immediately, the mind starts asking uncomfortable questions.

Am I doing something wrong?
Should I change the fasting schedule?
Am I eating the wrong foods?
Is this even working?

Those questions are natural, but reacting to them too quickly can lead to unnecessary adjustments that disrupt a system which was actually progressing.

In many cases the best decision is simply to hold the line.

Structured fasting, disciplined eating and consistent training take time to produce visible changes. The body adapts gradually, not instantly.

And when stubborn areas finally begin to shift, the progress often appears more suddenly than expected.

Understanding this removes much of the emotional reaction to daily scale readings.

The scale can still be useful, but only when viewed as part of a much larger picture.

Fat loss, fitness and long term metabolic adaptation are rarely reflected in a single number.

They are revealed through patterns that emerge over time.

The challenge during this phase is rarely a lack of progress.

The real challenge is maintaining trust in the structure long enough for the body to reveal the changes that are already taking place.

This is why the Beyond 20:4 experiment tracks multiple variables at once.

Scale weight, training performance, food timing, recovery patterns and metabolic signals all interact. Observing those patterns over months rather than reacting to individual days has become one of the most valuable lessons from the process.

*Photo by Markus Winkler on Unsplash

Can You Improve Athletic Performance with Extended Intermittent Fasting as a Vegan Athlete?

Chris Dunkerley — Tue, 24 Feb 2026 22:09:22 GMT

Most experienced intermittent fasters understand one thing well:

Around 10-12 hours into a fast, the body begins shifting more heavily toward fat as a fuel source.

That metabolic transition is often where the conversation stops. The “fat-burning window” becomes the headline.

But advancing performance doesn’t stop there.

And for plant-based or vegan athletes in particular, the real question isn’t whether fat oxidation* increases.

It’s whether speed, strength, recovery and muscular development can advance, while protecting structured fasting.

What I Thought I Knew

By mid 2025, I had progressed from 16:8 in 2022, into a consistent 20-21 hour fasting rhythm.

I was exercising on average twice a week and my energy felt stable. I was doing approximately 6,000 steps 3 days a week commuting to work, plus hockey training for 2 hours on a Wednesday evening, and a hockey match on a Saturday.

My body weight was stable and my overall health very good.

As I’ve been on a fully plant-based (vegan) diet since 2018, by 2025 it was much more in line with fresh whole foods, tofu, lentils, rice and greens. Discipline wasn’t the issue.

On paper, everything looked right.

But when I increased structured running volume in 2025, something didn’t align.

Endurance improved, but visible definition didn’t seem to shift at all. And as I began layering extended fasts into my programme, performance, sleep and previously stable fasting capability began crashing. That was the moment the experiment began.

Unknown Territory as a Plant-Based Athlete

I was in unchartered territory and there wasn’t a podcast in sight that discussed plant-based diets with extended intermittent fasting AND performance.

I should say here that I’ve always played hockey and always been running to some degree. In 2025 I was 3 years into intermittent fasting and already proved that athletic performance can improve on a basic daily 16:8 fasting window. The real question was, is it even possible to improve athletic performance while training and fasting beyond 20:4 and would it:

increase speed?
progress strength?
alter recovery?
stabilise sleep?
define muscle?

That question became the foundation of a more deliberate, measured phase of experimentation.

Where I Went Wrong

Before building a framework, I made mistakes.

I extended fasting windows too aggressively on key performance days.

I under-fuelled protein after sessions, particularly on heavy run or hockey days.

As part of an earlier experiment to test how the removal of salt, oil and sugar from cooking and food intake would affect my appetite, I encountered sodium depletion symptoms which clearly flagged issues.

Discipline and misunderstanding were overriding safety.

The result?

Unpredictable performance.
Inability to sleep, or get back to sleep.
Light-headedness.
Confusion and doubt.

As a person, I’m fully vested in intermittent fasting, and it is a non-negotiable part of who I am. I’ve experienced consistent benefits over time, and that’s why I wasn’t willing to abandon it.

But new additions and experimentation without structure was adding stress to my body which was compounded by factors I didn’t yet understand.

What Changed

I began researching, and introduced structure.

By profession, I work in UX and Conversion Rate Optimisation. Website design and lead-generation disciplines built on testing assumptions, measuring outcomes, and refining systems.

So I treated my nutrition and training the same way.

Variables tracked included:

Fasted vs fed sessions
Protein anchoring in first meals
Carbohydrate placement relative to intensity
Sodium timing before runs and lifts
Sleep response
Morning scale trends
Waist and relaxed abdominal measurements

On a plant-based framework, protein timing became particularly important. Not increasing total intake wildly, but structuring it with more precision.

It’s very easy to overeat fibre on a whole-food vegan diet built around legumes and vegetables, so the goal was absolutely not to eat more.

But instead, to eat more deliberately.

Early Results

Within structured guardrails, patterns began to emerge.

Fasted evening runs improved in pace, including breaking the 27-minute barrier for a 5.5km equivalent effort (which included being able to run effectively without the need for my inhaler which I’d been on for light asthma since after Covid).
Strength sessions progressed despite being performed in a fasted state.
Importantly, recovery capacity didn’t collapse, which is often the hidden failure point of extended fasting.
Respiratory control (and recovery) during high-intensity efforts improved.
Late-night “false hunger” reduced when sodium and protein were positioned correctly.

Not every session improved. That’s important. But the trend was clear:

Fasted training did not suppress performance.

When structured correctly, including deliberate plant-based (vegan) protein placement from sources like tofu and legumes, with sodium management, it enhanced metabolic efficiency without sacrificing output.

“Scientific evidence suggests intermittent fasting does not negatively affect athletic performance metrics and may support recovery and body composition improvements.” (Source: Nutrients systematic review)

The Structure I Was Missing Before

What I discovered during my experiment was that fasting plus performance is not about eating less.

It’s about:

When you eat.
What you anchor first.
How sodium is managed.
Which sessions should remain fasted, and which should not.

And that eating before some training sessions is ok.

How recovery is protected.
How sleep responds.

The full structure I have tested, including sodium strategy, protein hierarchy within plant-based meals, and my refeed sequencing, forms part of the broader framework explored in the book.

So, Can You Improve Athletic Performance While Intermittent Fasting Beyond 20:4?

Yes. But not accidentally.

And not by copying someone else’s fasting window from social media.

It requires:

Consistency.
Measured experimentation.
Respect for recovery.
An understanding that what works for one disciplined plant-based athlete may not work for another.

The goal is to understand how your physiology responds when variables are controlled.

That’s the work.

And that’s the journey this experiment continues to explore.

When CRO Meets Plant-Based Intermittent Fasting

Chris Dunkerley — Sun, 22 Feb 2026 21:09:49 GMT

There’s no shortage of information online about intermittent fasting.

There’s no shortage of advice about plant-based diets.

And there’s certainly no shortage of opinions on athletic performance.

But combine all three?

Very little exists that explores plant-based eating, advanced intermittent fasting, and structured performance training together, in a measured way.

This is my structured experiment combining plant-based nutrition, intermittent fasting, and athletic performance training.

Seven years into plant-based eating, I realised something uncomfortable.

I still couldn’t clearly explain what my own body was doing, despite training consistently,
fasting consistently for over 3 years, and eating a clean, whole-food diet.

Discipline wasn’t the issue, but I was experiencing:

Persistent bloated belly
Inconsistent morning scale weight swings
Uncertainty about food timing and physical appearance
Confusion around whether carbs, fibre, salt, or fat were responsible
Performance plateauing despite effort

There was an uncomfortable tension:

I was doing all the “right” things, but I couldn’t explain cause and effect.

And that really started to frustrate me.

Why CRO Changed Everything

By profession, I work in UX and Conversion Rate Optimisation (CRO).

At its core, CRO is simple:

You don’t guess.
You test.
You form a hypothesis.
You control variables.
You measure outcomes.
You iterate.

It struck me one evening:

What if I stopped consuming more nutrition advice, and instead applied structured experimentation to myself?

That was the start of what became Beyond 20:4.

Why Beyond 20:4?

Most intermittent fasting content lives in the 16:8 world (16 hours off: 8 hour eating window).

I’d moved well beyond that.

After gradually extending fasting windows over time, I was operating around a 20:4 structure, and eventually began testing 48-hour fasts within a training routine.

But I wasn’t measuring anything properly.

And without measurement, progress (and slippage) is very hard to quantify.

So I began systematically tracking:

Weight (daily)
Waist circumference
Relaxed belly vs tensed belly
Training sessions
Food composition
Sodium timing
Fibre density
Water and alcohol
Subjective hunger signals

What I Noticed

Some observations were immediate.

Scale weight fluctuated dramatically based on sodium timing, processed carbs and alcohol (more on that another time).

Evening fibre affected next-morning appearance.

High-oil plant-based meals (which had previously been common) seemed to prolong bloating more than carbohydrate intake did.

Fasted runs did not reduce performance and in some cases, they improved pacing discipline.

As there is in CRO, the data revealed patterns that allowed me to stop guessing and identify where choices were sabotaging progress, and taught lessons to improve future performance.

What Surprised Me

A few things genuinely challenged assumptions.

Extended fasting did not erode strength when the refeed structure was deliberate, and limited.

I removed added oils entirely during Phase 1.
What changed wasn’t dramatic, but abdominal consistency became more predictable.
Whether that relates to overall fat density, digestive load, or my own genetic predisposition is still something I’m exploring.

Electrolytes were less important than sodium timing in isolation.

Without understanding how foods influence my body, the best of intentions often back-fired.

Protein timing, particularly in later phases, appeared more influential than simply chasing total daily grams.

And perhaps most interestingly:

Performance sometimes improved when eating less frequently, not more.

What Didn’t Work

Assuming “plant-based” automatically meant optimised. It turns out that plant-based doesn’t automatically mean performance-optimised. (I've learnt a lot about plant-based performance nutrition, which I will share insights into another time).

Large fibre-heavy meals, late evening sugar, when clean carbs and protein had already filled glycogen stores, high-fat “healthy” meals (like nut dense overnight oats for example), that felt virtuous, but behaved differently physiologically.

Cutting out salt completely when layering physical exertion sessions.

What Changed

Gradually, patterns formed.

Feeding before fasting, and after (refeeds), became structured rather than reactive.

Carbohydrates were specifically chosen around performance sessions (as some work better than others)... as were salt doses.

I began to understand the nutrient load in different food types, and structure my meals differently to give my body what it really needed - as opposed to vegetable bulk volume.

Finding I could tie high sugar desserts to midday meals without sacrificing significant water retention the next day, AND avoiding the afternoon crash they normally caused when eaten singularly.

Strategies to avoid over-eating post fast strengthened and became second-nature.

Measured Outcomes

No transformations at this point, but definitive improvements.

A downward trend in waist measurements
Predictable water fluctuation during 48-hour fasts
High volumes of food are not needed before a fast, and;
Can negatively affect the refeed afterwards.
Reduced unpredictable bloating
Faster 5.5km times (breaking sub-27 minutes recently)
Increased hockey training and match fitness
Stronger gym execution under fatigue
More predictable hunger rhythms
Better sleep consistency

But after 11 weeks, stubborn fat was still clinging to my gut.

So I began to plan Phase 2, which introduced a protein focus on meals, and additional strength intensity training to surge physical development and push fat out.

What I’m Still Testing

Currently I'm about to enter week 15, which is week 3 of 8 in Phase 2, and exploring:

Protein density thresholds within plant-based meals
The upper limit of fasting windows alongside strength development
Sodium placement before different session intensities
Whether visible body composition can improve without increasing total calories
Where recovery ceilings begin to show

The experiment continues.

Because adaptation never stops.

Individual Variability Matters

What works for me may not work for you.

Your training load, hormonal profile, stress exposure, digestion patterns, sleep quality and lifestyle will all shape outcomes differently.

This is not prescription, but exploration.

When CRO Meets Fasting

The most valuable shift wasn’t dietary.

It was psychological.

Instead of reacting to scale numbers, I was able to understand and predict them based on food intake and timings. This elevation of perspective not only protected my sanity, but allowed me to forge ahead testing other variables.

A Question Worth Asking

What would happen if you applied structured experimentation to your nutrition instead of consuming more advice?

What would you learn about your own physiology?

That question is what continues to drive this project.

And it’s why this blog exists.

To document lived testing at the intersection of:

Plant-based eating
Advanced intermittent fasting
Athletic performance

Not as theory.

But as measured experience.

The experiment continues.

Intermittent Fasting Alone Doesn’t Always Guarantee the Same Results

Chris Dunkerley — Sat, 21 Feb 2026 23:17:07 GMT

In October 2023, I moved my intermittent fasting window beyond 16:8.

Not as a dramatic decision. It just evolved. 18:6 became 20:4. Eventually I was averaging around 21:3 most days without forcing it.

At that stage I was not measuring much. No structured tracking. No detailed logging. Just consistency.

Plant-based, yes. But not especially refined. Oil intake and oil was high. Sweet things were normal rather than occasional. I trained regularly, but without much performance intent.

Even so, intermittent fasting worked.

Weight regulated. Energy felt stable. Discipline improved. Tightening the eating window alone made a visible difference.

If the story stopped there, I would probably say that was enough.

But in mid 2025 I began running more seriously as part of hockey training, and progressing pace was a big driver. Timed efforts, structured sessions, fitter players to keep pace with, and a target to achieve.

That is when the lens sharpened.

Endurance and fitness were improving, but physically I looked broadly the same. My gut wasn't reducing and I wasn't seeing month to month changes to it in any obvious way.

Some sessions felt powerful. Others felt empty for no obvious reason. This erratic progression, coupled with no real physical belly improvement (despite eating a whole-food plant-based diet), became unbearable.

I was in a place I didn't understand and felt like I was flying blind.

This discomfort is what led me to formalise what became Phase 1 of Beyond 20:4.

Across my cooking, I initially removed oil, sugar and salt completely. (Happily, as my understanding has grown, sugar and salt now appear more regularly). *Do not remove salt from your diet while progressing performance. It is not safe and I'll write a blog on why.

Meals repeated on purpose so variables stayed stable and I tracked all the data. Weigh-ins daily, evening waist measurements, food and water intake, alcohol, fitness sessions, issues - everything I needed to test with clarity.

Over the 3 months of Phase 1, my body fat reduced further. Energy became more predictable. Patterns in water retention and refeed response became clearer. Discipline tightened again.

But one thing stood out.

A strict fasting window alone does not guarantee ongoing body composition change or performance improvement.

Despite the hype you see on social media, extended fasting alone does not always mean that one day you wake up with the perfect physique.

What works for one person at one stage will not necessarily work for another. Physiology, training history, and stress load will be different. Even plant-based diets vary massively in composition and energy density.

Which is what led me onto testing new questions in Phase 2:

Does building strength help shed the stubborn fat that clings on?
Can muscle definition improve while maintaining tight fasting windows?
Can a plant-based diet support higher protein demands without loosening structure?
Does electrolyte timing influence performance output and next-morning weight?

At the time of writing, Phase 2 is about to enter the 3rd week of 8, and I'm excited for the week ahead.

Short answer: Intermittent fasting can stop producing visible changes once the body adapts to the routine. When that happens, training structure, protein timing, recovery and overall diet composition often matter more than simply shortening the eating window.