How Long Should You Fast?

37 min read

What You’re Getting Into

  • The core requirements of a successful diet
  • The types of fasting protocols
  • How fasting can enhance fat loss
  • Ranking each fasting protocol
  • A few potential downsides of fasting
  • How many hours should you fast

Ranking The Best Fasting Diets

Have you shoved your breakfast away and got yourself ready to take a stab at fasting? You may well be, and should be, confused by the sheer amount of options to pick from. Well, get strapped in for a guide that will be scraping the barrel by the time it draws to an end.

It’s going to be a long one, because I’m going to from practical advice and science. Don’t worry, I won’t start throwing obscure biological pathways at you, this article will only serve as a primer if you want to delve further into the hard science of nutrition.

And when it comes to fasting, there’s a whole lot to choose from, so fill your boots.Here are the big ones that each occupy a different spot on the timeline

  • Overnight Fasting – 12 Hours
  • Time-Restricted Feeding – 12-16 Hours
  • Intermittent Fasting – 16-20 Hours
  • One Meal A Day – 22-23 Hours
  • Alternate Day Fasting – 36 Hours
  • Water Fasts – 3-7 Days

And the ones that don’t technically work with the rules of fasting, but still tick a few boxes.

  • Protein Modified Fasting – Eating an exclusive protein diet for a week or so
  • Fast Mimicking Diet – Eating low protein on a hypocaloric diet
  • The 5:2 Method – 500 calories per day for two days in the week

There’s plenty more down in the rabbit hole, but that’s due to the need for every entrepreneur to come up with their own spin. 

This article will put this entirely through the binoculars of fat loss. The successful kind, where you actually get to keep the weight off, and the profits don’t just die off after a blistering opening week. 

So I’ll assume that you want to shift a few pounds, without running the risk of muscle loss. Each of the variations in the list will service that to some level, but that won’t necessarily make them optimal. And optimal is exactly what you need if you’re either the type who struggles to shift weight, or the kind that wants to take it on with brutal efficiency. In any case, I’ve got you covered. 

Reading through this will give you the necessary handle on the science that surrounds fasting, and my own personal recommendation based on the facts at play.

The Pillars Of An Optimal Diet

First it’s worth covering the essential features of a well-formulated weight loss programme. As a basic requirement, a good fat loss protocol has to cause a degree of weight loss. Even without counting calories, there need to be rules and effects, such as appetite suppression, that encourage you to keep a deficit. 

But we need to tick off a few more boxes if we want the lost weight to be fat, rather than a mix of fat and muscle. While some muscle loss becomes inevitable towards single-digit body fat figures, you should always be fighting tooth and nail to hold on to it.

Resistance training can definitely help, but an optimal diet has to have some muscle-protective effects on its own. The amount of muscle you carry is directly linked to your metabolism, which means it needs to be carefully managed over the course of weight loss.

Losing considerable lean mass makes for a worst-case scenario, where the body increases negative adaptations in an effort to keep you from wasting away. T3 drops, leptin drops, ghrelin rises, all in a desperate bid to prevent starvation. Even if you’re not the type to worry about muscle, it’s going to be necessary in preventing the metabolism from tanking when you’re still six weeks away from the finish line.

Along the same lines is the matter of improving insulin sensitivity. The hormone insulin acts as a gatekeeper to storage cells, and resistance in the brain and muscle receptors play a huge role in creating an obesogenic environment. There should be a mechanism that erodes that resistance as the diet goes on. 

High protein is another key feature in making a diet tick, but veering towards quality control goes outside the scope of this article. Fasting needs to be seen as a tool that has beneficial effects even without accounting for the type of foods that find their way on your plate.

Stress balance concerns the ability of the diet to induce some stress on the body, but not so much that it becomes difficult to recover from. Ultimately, you’re going to have to inflict yourself with a degree of discomfort in order to lose weight. It’s not meant to be a walk in the park. If it is, you’re unlikely to be getting the most out of it. Being exposed to pulses of stress builds resilience, which will improve dietary discipline, while alleviating symptoms of chronic stress.

To give you the tail-end of it, an optimal diet needs to push you outside your safe space.

Finally comes the necessity to encourage and reinforce consistency. No diet’s going to save you if you skip the rule book every few days. If it’s too hard, that’s not your fault. But it is your fault if you don’t adjust or change diets. Otherwise you’ll just keep tapping into the same negative spiral. You have a couple of good days, get complacent or start to flag, take the mission off the rails, and dust off to start again. It’s brave, but it doesn’t lead anywhere.

See My Article – Bulletproof Habits

So here are the features of a well-structured diet in brief.

  • It should encourage a caloric deficit
  • It has a muscle protective effect
  • Increases insulin sensitivity
  • Supports high protein
  • Builds resilience
  • Allows consistency

It’s likely that you’ve got a solid idea on what fasting is about, because everyone and their mother seem to be on it right now. It’s much on the level of cross fit, where the user feels like they’re in on a secret, and has a righteous moral duty to let you know about it. But I’ll give you the brief version of what entails a fast, and then go further to provide a roundup of the science at play. After all, wouldn’t want to know why you’d put yourself through all the pain?

Fasting – This Isn’t About What’s On Your Plate, But When It’s Served

As a quick but necessary disclaimer, fasting is not a complete diet, in the sense that there’s no protocol for the type and quantity of food in the programme. And while it can bring home great results without the need to count calories, for the best results you should be combining it with some level of a meal plan. It could be paleo, it could be low fat, it could even just be a portion-controlled version of the average obesogenic western diet.

Now I do have a strong candidate for quality control, but I’ll leave that for another article. Here I want you to just completely settle in and get to grips with food timing and appetite control.

See My Article – 7 Tips For Intermittent Fasting

The Basics Rules Of Fasting

1. Fasting can be done for a spell as short as 12 hours, and can stretch over weeks, although that’s strictly to be taken under medical supervision.

2. Pigging off the back of that, if you’re pregnant, have diabetes, you should seek out more specialised advice than this guide. I’m in no sense a medical expert, but rather a dieting fanatic who seeks out the best weight loss tools.

3. No calories allowed, although coffee gets a pass as it can actually boost the effects of fasting and autophagy, while adding negligible calories.

4. However, the standard bulletproof coffee with fancy butter mixed in, is not a fast. It’s ketogenic, it can help suppress hunger and boost ketones, but it interrupts autophagy (cell-repair)

5. The full effects of fasting are only gained by avoiding ingesting anything that gets the digestive organs working.

6. Another exception to the rule besides coffee, can be electrolytes. For longer fasts, they’re a necessary addition to counter the sodium excretion that occurs when insulin is low.

The Insulin Problem That Fasting Fixes

  • Getting an early jump on the mechanisms of fasting is going to work out great for you later in the article, as I’m going to explain how each protocol fits in the fat loss process.
  • Fasting is based on the idea that sometimes, eating nothing is better for fat loss and metabolism than simply restricting calories.
  • This manner can create a metabolic shift from a carb-fuelled state, over to a fat-based one.
  • The benefits of this include improved blood sugar control, fat utilisation (lipolysis), better insulin sensitivity, appetite suppression, and autophagy.
  • For this to happen, insulin has to be taken out of the picture, as the hormone is inherently anabolic and opposes any attempt at lipolysis. It’s effectively a break on weight loss.
  • All of these changes result in a system that’s better at handling incoming calories.
  • Therefore fat storage is reduced, and weight loss becomes easier.

0-8 Hours – After the last meal, the body stays in the absorptive phase, which can take as much as 8 hours to wind to an end. Calories are digested, used, or stored according to necessity

12 HoursLiver glycogen can be depleted at this stage, but this is going to hinge on a few factors. Activity speeds up the process, but if you start the fast fully topped up, it can take up to 36 hours to hit the bottom of the barrel. Bear in mind, it’s incredibly easy to fill up liver glycogen stores, as it typically gets capped at 70-100 calories. If you wanted a takeaway from this information, don’t overdo the eating window. Bringing down liver glycogen is a critical step in making the best of fasting.

14 Hours – Providing there’s no more supply of glucose coming from the liver, the body switches to breaking down lipids from adipocyte stores, and using them as triglycerides.

16 Hours – Because triglycerides can’t pass the blood brain barrier and be used to keep the brain running, the liver breaks them down further into ketone bodies, which are small enough to pass through

18 Hours – The rising ketone levels completes the metabolic switch in fasting, providing a new type of fuel that doubles as a potent signalling molecule. This is the stage where you’ll tend to feel a boost in energy. Ketones are appetite-suppressive, so you can use that to push the window out a little further.

20 Hours – Autophagy begins to ramp up. This process includes cellular recycling, repair and the breaking down of misfolded proteins, and ebbs and flows over the course of a normal day. It’s a crucial part of building better immunity and stress resistance. The catch is that autophagy is inhibited by the anabolic MTOR pathway, which is stimulated by insulin and amino acids. So to allow the body to really fulfil its role in repairing old tissues, you have to be able to turn off the MTOR switch. Fasting is a natural tonic for that problem., as it shuts off MTOR and increases CAMP instead. CAMP is the cellular switch for times of scarcity, and improves your ability to utilise fat and perform endurance exercise.

24 Hours – At this point, you will have gone through the greatest benefits in insulin reduction and lipid mobilisation.

40 Hours – Even on a high carb diet, you’ll have reached full ketosis, as the liver will be fully depleted. Autophagy will be at its best for causing adaptation, but muscle catabolism will be at its highest, as the body breaks down amino acids for glucose. This is a process known as gluconeogenesis. 

72 Hours And Beyond – At this stage, medical supervision is recommended in order to account for any side effects that occur with this level of deprivation. Cognitively, it gets surprisingly easier to manage after the first couple of days. But strength and muscle-protection will be compromised in leaner individuals.

Why Fast For Weight Loss?

If you’ve been one of those traditionalists sticking to the militant routine of three meals backed up by comfort snacks each day, fasting might have initially appeared an alien concept. You get hungry after going a few hours without grabbing a power snack, so how on earth could you run on an empty tank for an entire day?

It’s a difficult aspect of fasting to grasp, but eating nothing often results in less hunger and more energy than opting for the usual weight loss approach of dramatically trimming down portion sizes.

To get an idea of the mechanism at play here, you only have to look at the effects of ghrelin and blood sugar. Ghrelin is a hormone that drives hunger. When it racks up, you tend to feel a strong survivalist urge to find something edible before you start to shut down. In reality, it’s just a sharp pulse that will generally fade away within the hour, but it probably won’t appear that way.

When you give in to the pressure and eat a bowl of cornflakes, blood sugar spikes and drops. The result is a spell of hypoglycemia that induces lethargy and yet another surge in ghrelin. The body responds to rapidly falling blood sugar by violently prodding you to top up again. 

Maybe this reflex isn’t so apparent during the early stages of fat loss, best labelled as the honeymoon period, but a significant weight drop will inevitably cause the body to fight back. This makes for one of the best aspects of fasting, as it completely changes the dynamic by sidestepping the twin threat of hunger and post-meal rebound.

Unfortunately, the feeling of hunger is so intertwined with emotion, that it can be extraordinarily difficult to distinguish as a desire, rather a necessity to eat. The best course in these situations, when dealing with the unknown, is just to test the waters a few times. Just cautiously, and without treading too far beyond the normal routine. The general starting point for attempting fasting is a cozy 16 hours. Assuming you avoided the temptation of a midnight snack, you just have to distract yourself long enough to get past the breakfast hour.

That’s all it takes. Chances are you’ll realise that the discomfort becomes a little underwhelming after the first few tries. You’ll probably wonder whether you’ve stumbled on the biggest hack in dieting. You didn’t feel like battling with starvation, in fact, your energy rose as the morning stretched on. Less time spent eating and digesting meant more room for being productive, even if that’s just punching out a few emails.

This is where the danger comes in. If fasting is so easy, why stop short at 16? If the longer you last, the more fat you burn, why not stretch it out to the next day? 

This assumption is technically accurate, as the metabolic shift created by fasting has great potential for becoming better at lipolysis, or fat burning. As the hours of plate waving start to mount up, blood glucose starts to plummet. This could be a bad thing, the empty slot is filled up by the mobilisation of triglycerides from fat stores.

Wait it out even further, and the liver will start to synthesis ketone bodies to supply the brain. This level of adaptation makes for the ultimate goal of metabolic flexibility, which in turn makes fat-loss that much easier by enabling you to seamlessly transition from digestion to body-fat utilisation without a hitch.

Is This The Case For Prolonged Fasting?

Since more time spent without food creates a ramping up transition from glucose burning to lipolysis, you could infer that the best fasts would be the ones that stretch into the next day. And if you go with this assumption, then you’ll be guilty of trying to jump into a foreign experience with both feet. It’s easy to get carried away in the hype of a programme that is actually getting the job done. 

Fasting can be done for multiple days with little issues, and no real cap on the distance you can go without risking literal starvation. A very lean individual can still hold 90,000 calories in body-fat stores, so there’s plenty of ammunition for drawing the fast out over weeks if you really wanted to. 

And while skipping meals for a week becomes long enough to warrant medical supervision, a couple of days isn’t a problem for general populations. But now you’ve got a decent grasp on the process involved, this is where I’ll bring in the merits and risks of each of the fasting protocols. 

Once you’ve read through this list, you’ll be in a great position to make the call and pick your weapon of choice. Afterwards, I’ll lay out my own recommendation, but truthfully, that’s going to be a subjective one. What works for me, doesn’t necessarily work for you. There are way too many highly varying factors at play when it comes to getting the midriff tapered down.

Scoring The Fasting Protocols

Overnight Fasting – 12 Hours

This is just a 12 hour fast. This makes next to no difference on fat loss, and it’s far too short to cause a metabolic shift to fat burning. At 12 hours after your last meal, you’ll have finished the absorptive or digestive phase, but the body will still be running on liver glycogen. This is going off a risky assumption that you’re not on a ketogenic diet.

While an overnight fast can be a big step towards the light for chronic midnight snackers, it doesn’t do much other than ensuring you get a good night’s rest. 

Caloric Deficit – 2/5 – It will eliminate late night drinking and eating, which tends to be statistically where decision making, and therefore food choices, is the worst. You’ll likely get a deficit of 10%.

Muscle Protection – 3/5 – No risk of catabolism in such a short span

Insulin – 3/5 – Nighttime is where you’re most insulin resistant, so it’s not a great time for carbs.

High Protein – 3/5 – Plenty of time to get everything in, it’s a 12 hour feeding window

Resilience – 1/5 – It’s extremely routine once you learn to let go of a few habits

Consistency – 3/5 – Besides late night drinking, you’re not going to miss much, which will help you stick to the plan. However that also means that you won’t feel so inspired, as results won’t be so quick to take shape. 

Time-Restricted Feeding (TRF) – 12-14 Hours

TRF is done for 12-14 hours, which is the standard tonic for people stepping into fasting. It’s not especially difficult, but there can be an uncomfortable hour or two at daybreak when you tiptoe past the appointed breakfast time.

There’s no need to skip breakfast in the fasting starter pack. If you were to have your last meal at 6 pm, you’d just push the bacon a little further over to 10 am. It’s simple, effective, and this makes it great for everyday practice.

At 16 hours, you’ll be using triglycerides instead of glucose for most of your fuel needs, and ketone levels will start to have a small effect. In case you’re wondering where they fit into the picture, ketones are the holy grail at the end of the metabolic shift. The more you can raise them, the more the body can learn to use them.

Ketones do much more than weaponise fat loss, they are extremely potent signaling molecules that lower inflammation, develop stress resistance, and supercharge the brain. So an optimised fasting programme needs to get the best out of them.

TRF is, unfortunately, a little too short to have much of an effect here, the level of ketones at this point still won’t be enough to cause adaptation. In terms of metabolism, it will improve insulin sensitivity over time, which helps glucose absorption and blood sugar control.

Time Restricted Feeding, popularised by S.Panda in the Circadian Code, is actually more of a means to improve energy and digestion by adhering to the circadian clocks in the digestive organs. It’s an entry point for fasting, but it’s not going to specialised to weight loss, particularly because it cuts off a little too early.

Caloric Deficit – 2/5 – The improvements to insulin handling will result in less hunger signaling, reinforcing a deficit of around 20%.

Muscle Protection – 4/5 – This is boosted by increased energy, which leads to better performance and recovery, ideal for muscle building.

Insulin – 3/5 – You’ll see significant boosts over the course of the diet, allowing better nutrient absorption. 

High Protein – 3/5 – The hours you miss out on probably weren’t go to be high protein affairs anyway

Resilience – 3/5 – It’s still easy, but you will have to push past that ghrelin pulse, at least over the first few weeks.

Consistency – 3/5 – The increase in energy and recovery should spur you on, regardless of having to hang in the background in work parties.

Intermittent Fasting (IF) – 16-20 Hours

IF is a significant step into the frontier of food abstinence. Improves to insulin sensitivity will be significant over a matter of weeks, and it’s pretty sustainable. You’re just dropping down from the regular three meals to two, maybe even with a snack thrown in between.

The best part of IF is that it allows you to make the most of that window that appears once you wade past the initial pangs of hunger. Because the consequential fall in ghrelin coincides with rising ketone levels, you should feel a raised level of cognitive and physical energy, the type that you’ve never had in the morning. 

The body is initially producing triglycerides to supply fuel, but they are too large to make it past the blood-brain barrier. As glucose continues to fall after the end of the absorptive phase (digestion), the liver starts breaking down triglycerides into ketones. These wonderful creatures supercharge the brain, supplying it with clean energy that comes with anti-inflammatory and anti-excitatory properties.

That state can be immediately diminished upon the first meal, as a glucose-laden meal significantly suppresses ketones. Ketones themselves can’t exert an effect on the brain when glucose is elevated, although exogenous ketones have been shown to boost non-fasted, high carb athletes. Generally though, you won’t experience the best effects of ketones until you’re either fasted, on a low-carb diet, or significantly fat adapted. So when you’re starting out, it’s well worth holding out a while longer before breaking the fast.

When planning out the timing of your first and last meals, it’s worth considering two of the mechanics at play. For one, shifting your last meal earlier into the evening will allow the digestion to wrap up most of its duties before the onset of sleep, thereby giving the body the chance to dedicate its resources towards recovery overnight. 

As the second point, pushing the first meal further into the day will take advantage of raised insulin sensitivity in the morning, where it’s at its best. Eating tends to blunt that state, so keeping the fast going longer will make for better nutrient absorption in later meals. 

Otherwise, in a run-of-the-mill three-meal day, dinner coincides with insulin resistance, and a greater chance of fat storage. These all make for crucial details in an optimal diet, as it’s not just about what you eat. How the body chooses to handle and use calories can play a deciding role in turning you from fat to fit, or the reverse.

See My Article – Should Bodybuilders Fast?

Caloric Deficit – With counting calories, the deficit should end between 20-30%. 

Muscle Protection – 5/5 – Ketones are anti-catabolic in nature, providing an alternative fuel source instead of glucose, which can be extracted by muscle breakdown. The spike in cortisol and adrenaline towards the end of the fast should actually increase energy if you choose to train at this stage.

Insulin – 4/5 – Insulin will reach even lower levels, further eroding resistance in the receptors.

High Protein – 3/5 – There is a risk of feeling an urge to break the fast with a mountain of carbs, which will naturally make for low protein content. 

Resilience – 4/5 – You’ll completely push past the initial ghrelin pulse, and autophagy will result in stronger cells.

Consistency – 4/5 – IF allows for consistent meal times and a better relationship with hunger.

One Meal A Day – 22 Hours

Obviously, you’ll be doing well if you’re taking two hours to finish a meal, so the true version of OMAD would be closer to 23/1. But since this fast is quite a long one, it’s advisable to break it with a small meal. Capping off your feat with a giant plate of food can fan the flames of emotional eating, and it’s surprisingly easy to offset the deficit of a long fast if you put your mind to it. So it’s worth splitting up the main meal to keep the appetite under control.

That’s not to take any shine off OMAD, as it’s remarkably potent at bringing the effects of autophagy and ketosis into an everyday format. While you don’t have to do this every day, and some programmes just called for a few attempts per week, it’s perfectly possible to do this without needing time off. Fasting for this duration can induce some stress, as part of autophagy and elevated CAMP signaling, but it’s enough to build adaptive resilience without cranking anything up to chronic levels.

The space between 18 and 24 hours is what many would call the sweet spot. It’s easy to keep a deficit as long as you plan out the meals, the metabolic upgrades are considerable, and there’s nothing stopping you from building it into a daily repetitive pattern. You could, for instance, have the meal at 2 pm, and fast from there till the same time on the next day. Fasting through the evening shouldn’t involve any hunger issues, and the initial wave will come and go unnoticed as you sleep.

How To Build The Perfect OMAD

Caloric Deficit – 4/5 – If you can eat that one meal without dreaming up extreme portions, the deficit should end up around 30-50%.

Muscle Protection – 5/5 – Protein breakdown is a 24-hour event, so you’re not going to compromise that by missing a few meals.

Insulin – 5/5 – You only need to tap into the insulin switch over one small part of the day, leaving a giant swath of time for building sensitivity.

High Protein – 2/5 – The problem is fitting enough protein into that one meal, another reason why I recommend splitting it over a few plates.

Resilience – 4/5 – Ketones can reach near 0.25-0.5mm over the course of OMAD, enough to gain some of its effects on cell resistance. 

Consistency – 5/5 – You can easily settle into a routine that repeats itself each day. Guesswork is taken out of the picture, the brain can recognise emerging patterns, and OMAD becomes a real habit. 

Alternate Day Fasting – 36 Hours 

This is a popular method with plenty of research behind it, and isn’t much harder than completing OMAD. After the first 24 hours, you’re likely to have to just go through one more ghrelin pulse, and the coast is clear.

Autophagy gets near peak levels, and you can expect to lose a significant amount of fat, which can be as much as 0.5lbs of fat in one fully fasted day. While that may not sound like much on its own, it will rack up considerably if you’re able to continue the caloric deficit over the rest of the week.

The issue here is that muscle catabolism becomes a real threat in lean individuals, although it’s been shown to occur less while carrying more body fat. This makes perfect sense physiologically, as even if you technically had 90,000 fat calories available at 10% body fat, you’d only be able to burn up a tiny fraction of that over the course of the day.

So to meet your metabolic demands, the body will have to utilise amino acids to make the numbers. This can be alleviated by including strength training, but you’d still need to refeed the day to recoup lost proteins. If you’re constantly in a deficit, that’s not going to happen. If you’re ending each ADF with huge piles of food, that’s tapping into emotional eating and therefore can’t be seen as sustainable.

Again, this is in the context of lean dieters, especially women, who tend to be more adversely affected by excessive amounts of stress. Most will get through this fast without a hitch. 

Caloric Deficit – 4/5 – The usual style is to eat at maintenance one day, and fasting the next. Essentially giving a 50% deficit.

Muscle Protection – 3/5 – The ketones will play a role in preventing catabolism, but it’s an unavoidable fact that you’ll lose some lean mass at some point. 

Insulin – 4/5 – It’s much the same as OMAD, although there could be some negative effects if you break the fast in the morning. Following that with a normal eating day can result in building back some insulin resistance by the evening meal.

High Protein – 2/5 – This naturally takes a hit, 

Resilience – 4/5 – You’ll completely push past the initial ghrelin pulse, and autophagy will result in stronger cells.

Consistency – 4/5 – IF allows for consistent meal times and a better relationship with hunger.

Water Fasting – 2-7 Days

The difficulty of this fast is going to hinge on the factor we’ve touched in ADF, the amount of extra ammunition you’re carrying around. It comes down to fuel availability. If you still have plenty of weight to lose, there shouldn’t be any adverse effects besides the occasional ghrelin spike and bout of dizziness. Even though glycogen is fully depleted across the body after the first few days, there will be enough calories available in fat stores to make up for the lack of food coming in.

Prolonged fasting can be a bridge too far if you’re looking for something that’s going to last you a few months. As I outlined at the beginning, this guide is focused on finding the best protocol for fat loss. While complete fasting is the ultimate caloric deficit, doing it excessively can lead to negative stress-based adaptations. The prolonged versions are ideally saved for a monthly or fortnightly event. Not for weight loss, but to clear up the deadwood and test your mentality against a bigger challenge. 

The strength of water fasting is more in the realms of autophagy, detox, and even as a way to step back from unhealthy eating patterns and reassess the routine. If you were to include it, I’d strongly suggest using it as an addition to a shorter fasting regime. In this case, both will complement each other, and throwing in a marathon every once in a while can help you better deal with the emotional chase for food.

Caloric Deficit – 5/5 – With no calories coming in besides a drop of coffee here and there, the deficit can reach the level of 10,000 or greater. Being equivalent to 3 pounds of fat, if we make the assumption that you don’t lose lean mass in the process.

Muscle Protection – 2/5 – During the second day, you will switch to burning a portion of protein. Not necessarily the type found in the muscle, but there’s still a risk, especially if you go straight back to eating on a deficit.

Insulin – 4/5 – Fasting to this stage can actually build some insulin resistance, which means you’ll have to be careful with the amount of carbs in your first meal.

High Protein – 2/5 – Nothing coming in from the diet, but the body will make up for a large portion by reusing body proteins.

Resilience – 5/5 – This is as good as it gets for autophagy, ketones, and their effects on stress resistance.

Consistency – 1/5 – It’s unthinkable to do this on a consistent basis while being relatively lean or juggling a social life.

Protein Modified Fasting, Bulletproof Coffee, Fast Mimicking Diet & The 5:2 Method

This is where I group together the ones that aren’t technically fasting, but come with similar benefits. PMF is an exclusive protein diet, that makes it great for muscle retention, but not so great at insulin modulation and energy. Simply put, you’ll lose weight, but feel like a flu victim while trudging through it.

The others are hypocaloric, and primarily fat based, so will do wonders for insulin levels. You should even get to spend some time in ketosis, which will help appetite suppression and curb episodes of hypoglycemia.

But since they all contain calories, they don’t quite fit the criteria. Looking at it objectively, it should be easier to sustain a huge calories deficit by avoiding the meal altogether, rather than giving yourself the trimmed down portions. When food’s on the menu, there’s a bombardment of senses to let a deprived body know that it’s time for a feast. Once you start eating, it might be difficult to reign yourself in and wait for a rampaging appetite to eventually subside.

The Best Fast

Fasting can be a huge shift from whatever diet you rode in on, and it’s advisable to start at a steady 16 hours before thinking of ramping up. The strongest feature of a diet is always going to be adherence, regardless of the special powers it can grant the metabolism. You get the dream summer physique by perfecting the average day. So you don’t want to be warring with hunger on a daily basis. Weight loss is inherently a stress, not necessarily a bad one, but it can turn negative if you’re driving forward without getting a chance to recover.

The style of fasting you choose should be built to last. It can easily become the latest item on the fitness fad conveyor belt, something you hammer out for a month or so and then completely forget. Why does this happen? The likeliest of answers is a simple one: burnout. 

It’s easy to get overly absorbed in the thrill of testing your physical and mental limits, and watching the scale drop every other day. Then motivation inevitably dips, or the body begins to fight back, and you instinctively retreat back to old habits. 

The Case For Intermittent Fasting

This is where intermittent fasting makes for a smart choice, because it’s a daily fixture. If each day is the same, with identical mealtimes, the brain will be allowed to settle into the loop and create new habits that will be crucial in riding out the ebbs and flows that come along.

Longer fasts are less effective for this reason. Metabolic resetting is a term I use to lump together all the ideas around detoxing. Whether it’s for some mental time-out, or a means to flush out toxins, extended fasting can be an immensely valuable tool. The fasts can range from 24 hours to a whole week and should be supplemented with water and electrolytes.

The issue here is that it won’t be particularly strong at habit-forming. It’s the sort of idea that you test out once a month, and with that level of frequency, it’s easy to get distracted and drop it altogether. 

And while you could technically lose more weight by fasting for longer than 24 hours, it won’t be a huge dent in the grand scheme of a weight loss programme. A few thousand extra calories burnt would still be less than a pound of fat. The scale might tell a different story, but that’s likely to be helped by losses in lean mass and water weight. 

Keeping this in mind, I’d highly suggest only using extended fasts as a bonus feature tagged onto an intermittent fasting regime. Which we’ll just label as IF from now on.

To get the best effects IF should be done practically every day of the week, or at least spanning work days. The feeding window can be as long as eight hours, offering plenty of time to get your meals in.

Once You Settle In – The Optimal Fasting Window

There is going to be a lot of context waved to the side in the state I’m about to make, because there’s a bunch of lifestyle and individual factors that drive the choice of the perfect fasting window. But if I were to pick up the average Joe, I’d side with OMAD as the tip of the spear for fasting for weight loss.

There’s a huge window of time for the body to rest from the rollercoaster of glucose metabolism and transition to ketone production and cell repair. And if you can pin down a certain hour for your meal, and hold on to it over a few weeks, the effects become supercharged. Hunger is often time and context dependent, so once the brain gets wise to the fact that a few meals have been wiped off the menu, and the pulses of hunger at breakfast and dinner can practically vanish. 

Three meals in a day is a relatively recent phenomena that became a social norm during the industrial revolution to enforce new working hours for labourers. Going back to the days of the Romans, people tended to have just one meal, at noon. Which is more or less ideal for pinning a time on OMAD. It’s not so far in the day that you start to flag, and it allows you to sleep through the first wave of hunger. By the time you wake up, assuming you haven’t wasted away during sleep, you’ll already have 16-18 fasting hours under your belt.

Ultimately, whichever fasting window you pick, it should fit in seamlessly with your daily routine. If you’re changing everything up to make space, that’s where burnout becomes a real issue. And even if you make it to the end of the diet, get the right numbers of flashing on the scale, what then? 

If you call it a day and wrap up the programme, then you enter the next challenge. Keeping the weight off. A tricky task that’s so much simpler if you’re still sticking with many of the eating habits that got you there.

Hey, I’m Sama, a natural bodybuilder who’s bought into the perks of keto and intermittent fasting. Why? When combined, the boosting effect on mental energy is unrivalled on any other diet. And the fat loss isn’t bad either. 

I’ve got a ton of recipes, guides and insights covering both of them, so check out some of them below.

More Diet Guides And Tips On My Blog

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