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Intermittent Fasting ("IF"), as a means to body recomposition and improved health

To begin, I want to credit Martin Berkhan, the owner of the site LeanGains.com/, and Brad Pilar, the author of the book "Eat, Stop, Eat". There is an excellent new article on the home page of Martin's site HERE, which I add because his experience with standard Western breakfasts (grain based) mirror mine exactly, and which I wrote about in the other article on the site here, entitled "Do you want to diet? Don't!". I will add as an aside that changing the composition of a breakfast can have markedly different effects than what he describes, though, so I do not want to get ahead of my argument at this point.

And yesterday, I noticed that Dr Mercola is now extolling the virtues of IF, too—let's keep an eye on this together.

Many of the ideas in this article began with what I read on Martin's site. And I will mention that Martin is not the only person recommending this approach to eating, but I like the way he expresses himself, and as a 'work in progress', bodybuilding-wise, he is very impressive. And I have had a long interest in manipulating the internal hormone environment, as readers of my book Stretching & Pregnancy and the article mentioned above will know. The reason for this is simple: depending on the relationships between a number of critical hormones, a molecule of (say) sugar entering your system can take completely different metabolic pathways in its digestion, with very different effects on the body as a result. This give the lie to nutritional 'truisms', like "a calorie is a calorie is a calorie". Like the rest of life, it depends.

And the larger context is the emergence of an approach to eating called "PALEO" (though there are many variations on this theme), which is motivated by a belief that our internal environment evolved together with the eating/activity habits of pre-agriculture humans (so, loosely, the inferred diets of hunter-gatherers and explicitly grain-free, vs. the diets of modern humans (last 10,000 years or so) who benefit from settled agriculturists. Put simply, the Paleo diet is vegetables/animal protein and small amounts of fruit in season, in contrast to the modern (post 1960) food pyramid, which features an additional, foundation, level of grain-based food—not available to hunter-gathers.

For those with short attention spans, and who demand the "take home" message from this article ASAP to save energy and, assuming you are male (Olivia's experiences with diet below), it's this:

Do not eat breakfast;

Have a coffee or two;

Eat first when the Sun is highest in the sky (so midday to 13:00);

Eat again when it is falling (so early evening, 18:00-19:00).

No snacks. Alcohol in moderation. You may stop reading here.

In contrast to the above, Martin's approach can be summarised as:

Do not eat breakfast; train before midday; and eat the three ordinary meals of the day between 12:00 and when you go to bed.

Keep in mind he is a bodybuilder training four-five days a week, so he needs those calories. His key concept/practise is the fast between the last meal of the previous day, and the first one of the following day. Further, he recommends that this fast be about 16 hours for men, and about 14 for women.

In this article, I want to consider how simply adjusting the timing of your meals can have a profound influence on what happens inside your body, even if the actual food you eat is the same (in terms of content and amount). Martin's approach is explicitly about how to maintain extremely low body fat levels (in his case, between 4–5%, all year around) and still increase muscle mass; his experiences with yo-yo dieting and his frustration with becoming obsessed with food make very interesting reading, but will be familiar to many.

If you know anything about bodybuilding, you will know that most follow a "bulk-up" phase and a "cutting" phase, the former as a means to increasing muscle mass (but at the expense of gaining extra unwanted fat, too) and the latter as the means to maintaining as much of that muscle as possible while getting body fat into the lowish single digits. Typically, this results in one's body weight oscillating 10–15Kg annually. Martin's fluctuations were much lower than these figures, but he wanted to find a way out of "diet hell" and freedom from obsession with food. I certainly resonated with these goals when I read his story.

But I am not a bodybuilder: I am an ageing male who is interested in getting as strong as possible, following a gymnastics strength training protocol (most here will know that the current Monkey Gym approach owes much to Coach Sommer's "Building the Gymnastic Body" system); and one of the core ideas in the gymnastic world is getting as strong as possible while staying as light as possible. In other words, it's about maximising one's power-to-weight ratio. I am interested in staying as flexible as I can, and maintaining a modest state of aerobic fitness for general health. The effects of the pursuit of these goals just happen to tick a large number of other boxes that relate to being optimally healthy. These include controlling the insulin/blood sugar relationship (two of Barry Sear's "four pillars of ageing") and, I believe, indirectly help reduce the other two (excess cortisol and excess free radicals) as well.

Excess cortisol is not explicitly helped by intermittent fasting so much as by the gymnastics approach to strength training, which can be characterised by short workouts using resistance that is close to one's 1RM (single repetition maximum), but not training to failure, which is what I used to believe was the most efficient approach to strength training, and about which I have written elsewhere. I will return to the "excess free radicals" aspect below.

In the past five months, my body weight has dropped from 85Kg to 75Kg, and my body fat is now around 10%. I drink alcohol daily, and I eat two generous meals of vegetables and some kind of animal protein, and a few (or more!) square of chocolate most days. The point about alcohol is significant, readers of my other "Diet" article will know, because when one is eating ketogenically (sometimes called low-carbing, wherein one burns ketones and free fatty acids instead of glucose, the way most people do) the liver's function is turned over to metabolising alcohol when it's present in the bloodstream—and this can derail the 'using one's fat for fuel' part of ketogenesis for the time it takes the alcohol to be metabolised. Depending on the type of alcohol and the amount, this might be 12 hours in 24—reducing the potential payoff from this dietary approach considerably.

In contrast, if on a mixed diet (fats, protein and vegetable carbohydrates) this effect does not seem to happen—but in the absence of urine testing (to determine the presence of ketones, evidence that the liver has returned its function back to using fat for fuel) I cannot be sure of this. What I can be sure of is the following: on the two-meals per day regimen, I am never hungry; I eat what I like, amount-wise and, as a result do not feel like I am denying myself; and then there's the red wine and chocolate aspects. For me it's all good.

A larger perspective is likely to be that, assuming one has fasted from the previous evening and eats after midday, and only two meals, it is likely that you are eating less calories overall, too (there is only so much one can eat at one meal). But this is not the whole story, I feel. Exercising in the morning (especially walking up and down the steep slopes of Mt Arrawang) definitely keeps the metabolism turning over. Better still would be doing a gymnastics or weight lifting workout before midday too—simply because much research has shown that high intensity exercise lifts the metabolic rate for up to eight hours following the workout—but the intensity has to be high. Running up hills; walking up really steep ones; or working at 1–5 repetition heavy resistance training all counts. A leisurely 30 minutes on the treadmill reading New Idea does not. Neither does walking on the flat—apart from riding a bicycle, walking is one of the most efficient human activities—and efficient means low intensity.

What about the improved health claim I made above? The most important one, by far, is controlling insulin secretion and improving insulin intolerance (another way of saying this is 'reducing insulin resistance'). Both these factors score high on any expert's recommendations to improve health. Both are assisted by decreasing the body-fat to muscle weight ratio, and this goal is much easier to achieve if insulin can be controlled, and if the muscles' resistance to insulin is reduced (because glycogen will be shunted into muscles rather than elevating and maintaining blood sugar levels).

And the equally important effect of both reducing total insulin secretion and reducing muscle resistance is the secretion of glucagon—absolutely critical if you further want to secrete leptin, because this hormone is critical to the brain knowing when to access your stored fuel (body fat) rather than creating new fat (lipogenesis). The biochemistry is extremely complex—but the short story is that to access one's fat and use of for fuel, the glucagon–leptin axis is critical. All you need to know is that insulin and glucagon have opposite actions (insulin: storage; glucagon: release). If you want to go deeper, there's a decent primer HERE.

Let's return to an earlier theme, Sears's two remaining "Pillars of Ageing", excess cortisol and excess free radicals. Excess cortisol production (through too much exercise; insufficient rest; excessive stress or fatigue) is unhealthy (I won't go into the details here except to say it weakens the immune system; promotes insulin resistance; promotes catabolism (antithetical to maintenance of muscle mass); and may be involved in auto-immune disorders; see an excellent Wiki HERE)—like insulin, there is an optimal balance and rhythm to its secretion. Exercising regularly, but not to failure (at least not too often) seems very desirable here.

Excess free radical production has been linked to the ageing process itself, cardiovascular disease, and cellular damage, and is thought to result from toxins (like smoking, air pollution, or pesticides in food) and even excess aerobic exercise, too, through oxidative stress. This latter reason is why I feel that the current Monkey Gym exercise protocol is optimal for health—short, relatively intense exercise periods with plenty of rest seems to benefit the body in this regard. The other approach to controlling excess free radicals is via antioxidants: eat vegetables! As I have written elsewhere, all the vitamins are phytonutrients (plant-derived substances); there are 13 generally recognised ones, but the test to name new vitamins is extremely restrictive, with the result that although thousands of new phytonutrients have been discovered (over 10,000 in all so far), no new vitamins have been named since 1953. See part II of the Sensible Eating article for more information on this HERE. It seems very likely that some of these phytonutrients will confer important health benefits similar to the essential vitamins—but which ones? The practical answer is to simply have as many different coloured and leafy vegetables at your two meals as you can locate and, if you are pushing yourself, consider supplementing with vitamin C, whose benefits continue to be uncovered.

I feel that intermittent fasting, along the lines suggested above, will provide the nutrients you actually need, without the excess calories—and make it much easier to acquire the body composition you want. But there is a deeper significance than one's appearance.

This next aspect is in the more speculative realm, I admit. I feel that this approach to eating has an important set-point resetting dimension. It is well know that the majority of the body's myriad reactions tend to settle around a point (homeostasis) and that most reactions come in opposite pairs, and that any aspect of the body is a 'resultant' of the interaction of two, or more, of these reactions (consider bone density or fat–muscle ratio). What I am thinking about here is (among other things) the incredible increase in auto-immune or immune system disorders in the last 30 years or so. I feel that some of these might be the effects of the aggressive proselytising on behalf of low fat diets—the inevitable consequence is that people have been recommended high carbohydrate diets as an alternative protocol. Good fats are crucial to brain and nervous system health and function. Add to this the now-conventional 5–6 smaller meals, or grazing-style eating, throughout the day—both resulting in higher than desirable blood sugar levels during our waking hours. Combined with lower levels of physical activity, and I think we can understand the present obesity epidemic. Part of this problem, I believe, is that the necessary optimal set point between glucagon and insulin is very difficult to achieve if blood sugar and insulin are relatively high (think 'area under the curve': if you are eating often or grazing, then over the majority of your waking hours, this will be the case). Overnight fasting is simply not long enough to achieve this balance.

The sense in my own body of paying close attention to all aspects of health (elimination, digestion, energy levels, body composition, strength levels, skin appearance, etc.) since beginning five months ago is that all have improved under the intermittent fasting regimen, with the exception of absolute strength levels, which were higher when I weighed 85Kg (or more). On the other hand, because I am over 10% lighter now, many body weight exercises are easier to perform—so functional (demonstrable) strength is now higher.

Olivia's experiences with the BodyTrim diet (eating every three hours, via three portion- and calorie-controlled meals per day, and two snacks, similarly controlled) is mirrored by one of our senior teacher's experiences. Both lost a lot of body weight, but both felt that they lost muscle and fat together and, if pushed to guesstimate, about 50/50. It seems clear that any calorie controlled diet ('calorie controlled" meaning that you eat slightly less than you expend) will result in your body weight dropping, and this effect is independent of what the composition of the calories are. For me, though, maintenance of as much strength and as much muscle mass as possible is desirable, not only because of my interests and activities, but for optimal hormone secretion: increasing the ratio of muscle to fat in the body is especially important for men, to avoid the physical feminising tendencies that result from too much oestrogen—itself resulting from a higher than desirable fat to muscle ratio.

In the original BodyTrim approach, a daily walk was the only recommended exercise; we both feel that this is insufficient stimulation to maintain muscle mass in the environment of calorie deprivation. She says, though, that on this eating-every-three hours plan, that she never felt hungry. I have never tried this approach and, moreover, feel that the hormonal disadvantage of regular feeding outweighs the benefits of losing fat and (this is the big one) when I eat, I want to eat as much as I feel I want to eat, and most men I know feel the same.

It might simply be the case that more regular eating suits women more readily than men. Certainly I never feel hungry, and nor do I control the proportions of the macronutrients I eat at the two meals. If you are female reading this article, you may care to experiment with the every-three-hours approach, making sure that you apply the Sears approach of paying attention to getting a modest amount of protein at every meal and snack.

Martin recommends a 14 hour fast for women, and a 16 and 16+ fast for men—and this is empirically derived. Certainly Olivia's responses to intermittent fasting suggest that playing with these times can be effective. She has found that a couple of boiled eggs at around 10:30 works perfectly when she first started following this approach, but recently has found that her body has adjusted to less regular eating, and we eat together.

Since I wrote this, I have had a long conversation with my friend Rama Prasad (of Ayurvedic Elements; see HERE); he has converged on a similar approach over the last few years, with this variation: eat breakfast, eat a big lunch, and no dinner. His experience with this (and his many patients' experience) is that this approach, if you can make it fit your lifestyle, works even better than the one advocated above. I will expand on this, but want to say now that this approach is identical to the "monk's diet" followed by Buddhist monks everywhere (very early breakfast, lunch before 12:00 and no food after 12:00) and Rama mentioned that patients who had sleep apnoea in particular had benefitted from this approach. And it reminds me of the old adage, "if you want to be healthy, eat like a King in the morning, a prince at midday, and a pauper in the evening".

I am posting this article here on the Forums to foster discussion. Please weigh in!

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I am no scientist nor researcher into eating habits - nor experimented with much fasting outside of participating in Vipassana retreats...

Coincidentally however -last week a friend emailed this to me, which 'weighs' in with part of the eat/fast/eat philosophy.

The documentary maker met some interesting people with different eating and fasting habits.


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  • 3 weeks later...

Thanks Kit for writing about intermittent fasting, yours and Olivis's experience.

Thanks Corey for posting this documentary presented by Michael Mosely. He has shed more light on the different options with fasting, the benefits for good health and the impact on aging. I loved that little mouse!

For myself, I lost 5kg in a month. Then I lost a bit of momentum. This film demonstrated there is plenty of choice with fasting. I like the idea of reducing portions to child-size, especially helpful when socializing. I feel it's possible to plan a fasting day at least once a week, including skipping daily breakfast. My time has been liberated!


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I have found the IF approach both fascinating and very worthwhile. To go against all the myths and truisms does present a challenge. 'Breakfast is the most important meal of the day', 'you need to eat regularly', etc.. What I like is that it is much easier than the opposite idea of regular eating. With the latter I found myself thinking about food and planning the next meal/snack. Knowing it is ok to be hungry and go without food for extended periods is a good feeling. For the first day or 2 I was doubting my ability to fast, but very soon it became easy and normal.

I too have lost weight. I guess I would have been regarded as lean and I have lost 5.5 kg or about 6% in 7 weeks. Importantly I feel better and no longer have mid afternoon flat spots.

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Hello Gary,

Initially, I was concerned about how I would cope when presenting workshops: I put out a huge amount of energy on these and I was worried about 'late morning fade" (I just made that up, but it seems to capture the concern!). And as you know from the recent Sydney workshop, that worry was groundless.

For men in particular, it seems we work better if we experience a period of hunger daily. When I say 'hunger', too, I don't mean famished or starving; just hunger. It's still working for me, even here in Spain.

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Possible connection of lack of 'late morning fade' to the prodigious amount of coffee imbibed at said workshops.. ? For me it was refreshing; I always hated eating breakfast as a child. Fasted morning walking, with some joint mobility and breathing exercises along the way, is great - especially through the bush!

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  • 2 weeks later...

Ah: coffee releases the catecholomines (adrenaline, noradreneline); these play in to the glucagon > leptin cycle (all help to switch the body to burning fat).

Plus the most important: I like coffee!

I envy your lush bush walks; very different to Mt Arrawang!

I am off to attempt the Grouse Grind this morning. Do the maths on the distance vs. height numbers.... "Mother Nature's Stairmaster" indeed!

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  • 3 weeks later...
  • 6 months later...

A couple of weeks ago, on SBS (I think) there was an excellent documentary on this very topic, very science-based, and referencing many groups around the world looking on this. I am going to try and locate this and will let you know if I do.

The studies focused on three aspects:

  • effect of high intensity short duration training on blood chemistry (think cholesterol types here)
  • effect on same kind of training training on brain development (think memory loss with age)
  • effect of fasting on both

Interestingly, they did not stumble across the idea of fasting (daily) that Kit is suggesting here. They came to rest (meaning to some sort of conclusion) that it took two consecutive days of fasting to achieve the best results (as per list above), but they weren't really fasting, they were going to something like 500 calories less than maintenance.

The result were pretty striking so I will ferret out this dock if I can.

Cheers Greg

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  • 3 months later...

A couple of weeks ago, on SBS (I think) there was an excellent documentary on this very topic, very science-based, and referencing many groups around the world looking on this. I am going to try and locate this and will let you know if I do.

Was that the BBC Horizons episode on fasting, or something else?

I've been practicing a 16/8 style fast for a while and I find it to be quite functional. The most dramatic results though are probably from my wife who practices the same fasting routine. She used to have intense migraines (with auras and other nastiness) every month like clockwork for the past 25 years or so. While I couldn't find anything too concrete, my research led me to suggesting that she attempt fasting. And from the month that she started fasting, combined with some AM exercise, her migraines have disappeared. So it has been a very productive experience for both of us.

Despite all that I'm very motivated towards experimentation, though I can't say with great confidence whether it's due to curiosity or boredom. Recently I've decided to try and Brad Pilon's fasting model instead of a 16/8 style fast that I currently do to see what kind effects it will have on my general health and training (I follow the Foundation gymnastics program from Gymnastic Bodies). I currently do very early morning fasted training with a meal at lunch and dinner without snacking. While I find it to be controversial, many people are very insistent not having some sort of post-workout nutrition is sub-optimum. While I haven't seen anything that would suggest it's that essential, I figure that a 3 month trial would at least settle the debate in my own mind. I wouldn't be adding anything substantial, just a very small protein focused meal post workout followed by my two regular meals during the day and no snacking and a 24 hour fast once a week. My goals seem to be identical to Kit's, I have no interest in building mass, but I'm curious what kind of differences I'll experience.

Does anyone else have any experience with the two different protocols?

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  • 9 months later...

I'll give this a bump.

I've been eating this way for about 8 months to great effect.

I wake up (6-7am), drink coffee then go train for 1-1.5 hours @ ~9am to 10am (crèche opens at 9am and closes at 11:30am).

Post training I eat a meal of eggs and fish (@~11:30)

Then I snack lightly snack during the afternoon mostly on cashews and almonds

Dinner is a huge salad with lots of mixed greens and heaps of veg, with a piece of meat usually BBQ'd (mostly to keep dishes to a min).

I then have a "treat" or two during the evening.

-wine, scotch, cognac, or craft/artisan beer


And if I'm feeling famished (once or twice a week)

- a sourdough grilled cheese or egg cheese mexi wrap

In bed ~10:30-11pm

So about a ~12hour fast.

I try and a snack on some fermented foods like homemade kimchi and homemade quark as well during the day.

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