Sunday, September 4, 2011

Intermittent Thoughts On Intermittent Fasting - Myth #1: A Higher Meal Frequency Equals a Higher Metabolic Rate.

Image 1:  Intermittent Fasting or Eating by the Clock? Debunking an old myth to give a new dietary paradigm its break (img hardwaresphere)
IF I had to name the one diet trend (besides "Paleo") that gets the most public attention, lately. It would probably be intermittent fasting, or "IF" as it is often abbreviated in the blogosphere. In view of the popularity of Duong Nguyen's guest-post and Adelfo Cerame's upcoming IF-based contest-prep coverage, I decided that it was about time to do what people often refer to as a write-up - personally I prefer the scientific term "review of the literature" - on what exactly is, or isn't, the magic behind the those mind-boggling success stories that keep popping up on bulletin-boards, bodyspace profiles and blogs all over the Internet.

Fasting - Ain't That the Fastest Way to Muscle Loss!?

If you look at the entourage people like Martin Berkhan from leangains.com have attracted, you will notice an unexpected heterogeneity in terms of people's dietary and athletic backgrounds. Everyone, from the obese kid who was refused by the casting crew of MTV's "Used to be fat" to the aspiring bodybuilder (like Adelfo) who is trying to reduce his bodyfat percentage into a range that no (living) human being has reached before seems to be fascinated by the idea that "fasting", a longstanding no-go for all dieters, suddenly appears to be the most promising, convenient and straight forward way to the body of their dreams.
Illustration 1: Classic perspective on the effects of "fasting" in the sense of simply not eating
It stands out of question - what we are seeing here, could be one of the most fundamental nutritionally paradigm changes, since the end of the low-fat craze. Not eating this was (and as this review will show often still is) the general consensus triggers a signalling cascade which sets your body metabolic switch into "starvation mode". This metabolic state, which, by the way, used to be an evolutionary advantage of the human race, is characterized by (cf. illustration 1)...
  • stress, i.e. an increase in catecholamines and cortisol, 
  • hunger, i.e. an increase in appetite and the tendency to overeat (especially on fast energy sources such as sweets), 
  • hormonal deficiencies, i.e. a reduction in thyroid (the active form T3 in particular) and sex hormones and 
  • reduced energy expenditure, i.e. a decrease in resting, as well as exercise induced energy expenditure 
Among the unwanted consequences of this "starvation mode", the reduced quality of life and the absence of weight loss or, in later stages, unwanted weight gain are probably the major concerns of the average dieter. Athletes, in general, and bodybuilders, in particular, have yet always been more concerned with the loss of muscle weight on and the accumulation of fat weight after the fast. Now if you look at Duong's results or Martin Berkhan's pictures, it is quite obvious that intermittent fasting does not entail this undesirable shift in body-composition - Duong's pictures rather suggest that he actually gained muscle while his body fat stores melted away.
Image 2: Never (!) let the scale put a spanner in your day. Use progress pics and a caliper instead.
I think it is wort mentioning, especially for the "mainstream dieters" out there, that body recomposition, as you often see it taking place after the initial water losses of the first day (especially) on low carb diets, will not show up on a scale. In fact, the figures this notoriously unreliable measuring device will be showing you may well increase, while the look of your body (judged by the mirror), your waist-to-hip ratio (measured with a simple tape) and the depth of your skinfolds (measured by a body-fat caliper) are improving. My advice for anyone who wants to look better and get healthier is thus to throw away the scale. Buy a digital camera, a full-size mirror, a tape and (optionally) a body fat caliper, take weekly progress pics and measures and set realistic short- and long-term goals.
Obviously, the whole issue of gaining fat while losing muscle leads back to the (as I am about to show in this first two installments of the Intermittent Thoughts on Intermittent Fasting series) unwarranted idea that only regular and frequent feeding intervals guarantee optimal metabolic function and prevent metabolic shut-down when dieting. A cursory search of the relevant databases reveals that there are more than 5,900 scientific papers which touch upon or dig into the relation of meal frequency, energy expenditure and weight loss. And while this does not tell you whether the hypothesis that the number of meals you consume within 24h really is a fundamental determinant of metabolic efficiency, it does at least show you that generations of scientists have cudgeled their brains over optimal feeding strategies. Nevertheless, the general consensus on what mainstream science consideres to be "optimal", i.e. multiple smaller meals distributed equally across the day, hardly evolved since the early epidemiological studies by Fabry et. al. in the 1960s (cf. figure 1).
Figure 1: The classical data on skinfold thickness (in mm) in 379 Czechoslovakian men aged 60-64 years Fabry et al. published in what probably is the most prestigeous medical journal in the world, The Lancet, back in 1964, still looms large in the public understanding of optimal eating patterns. (Fabry. 1964)
In view of the sheer amount of studies it would appear prudent to focus on the results of meta-studies (these are studies which rely on the results of a selection(!) of previous studies) such as the heavily-cited paper by Bellisle et al. (Bellisle. 1997) who conclude in their 1997 review of the literature in the prestigious British Journal of Nutrition:
Although some short-term studies suggest that the thermic effect of feeding is higher when an isoenergetic test load is divided into multiple small meals, other studies refute this, and most are neutral. More importantly, studies using whole-body calorimetry and doubly-labelled water to assess total 24h energy expenditure find no difference between nibbling and gorging. Finally, with the exception of a single study, there is no evidence that weight loss on hypoenergetic regimens is altered by meal frequency. We conclude that any effects of meal pattern on the regulation of body weight are likely to be mediated through effects on the food intake side of the energy balance equation.
At first sight, this conclusion appears to suffice to falsify the hypothesis that an increase in meal frequency would facilitate weight loss, once and for all, but if you scrutinize Bellisle's choice of words, you will notice that, after all, we are back to where everything began way before scientists even started to thinking about the potential effects of meal frequency on body weight and composition. We are back at "ground zero"; back to  what dietitians like to refer to as the(ir) "laws of thermodynamics". We are back at the fundamentally flawed "calories in vs. calories out" hypothesis. And we, or I should say, the majority of dietitians and large parts of the scientific establishment still bases their conclusions on the kindergarten interpretation of the first of three physical laws of thermodynamics, the oversimplified misapplication of which has been hampering theoreticians and practitioners for decades, now.

It cannot be all about "calories in vs. calories out"

Image 3: You can send in questions, comments and suggestions for future installments of this series via Facebook, Twitter or the comment-option on the bottom of this page.
If we really want to understand the real-world (and I guess you will concur that this is what it's all about) success of intermittent fasting, as it is reflected in countless blogposts, threads on bulletin boards and, meanwhile, even YouTube videos, we got to go beyond those paradigmatically blinded meta-reviews and have a look at the purported benefits and underlying weight- and even fat-loss mechanisms of intermittent fasting on a much smaller scale. This will probably take more than one or two blogposts and I encourage you to send in questions, comments and suggestions on which particular aspects you want to have covered in the upcoming installments of the Intermittent Thoughts on Intermittent Fasting series on the SuppVersity.

Although, I cannot divine your thoughts, I suspect that your questions, just like mine, will fall into one of the following three broad categories:
  1. Can intermittent fasting help me lose body fat?
  2. What effects will intermittent fasting have on my overall metabolic health?
  3. Is intermittent fasting a suitable diet strategy for (recreational) athletes in phases where they are looking to gain weight and/or improve their performance?
In view of what's been said before about the purported detrimental effects of "fasting", as in "not eating for a 'long' period of time", on weight loss and energy expenditure, I would further assume that you would agree that it would be prudent to cut the first sod by digging further into the longstanding myth (?) that an increased meal frequency, i.e. eating multiple smaller meals, instead of your usual three main dishes would increase the metabolic rate and thus help with weight loss.

Myth 1: A higher meal frequency equals a higher metabolic rate

In a handful of short-term studies, eating more frequently has in fact been shown to increase the thermogenic response to food intake. And, given the fact that the (re-)programming of our metabolism takes its time, this does not surprise me at all... Consider this, a body that got accustomed to a 3x800kcal feeding schedule over years (if not decades) has had more than enough time to adjust his post-prandial energy expenditure in a way that would ensure a relatively constant energy supply over the 3-5 hour "fast" to the next meal. If you think about it, you will probably realize that you have already experienced some fundamental consequences of this "priming" effect of regular feeding schedules occur when you skipped one of those regular meals: If you are not already used to intermittent fasting or on a very low carb diet, chances are, that you felt hungry and either snacked on the next best "food" (often what people are grabbin in situations like that does not really deserve this appellation) or felt compelled to overcompensate, which equals to "overeat", on the next scheduled meal.

Now, what would happen, if, on the other hand, you slid in three unplanned additional meals (and I am not talking about a high carb snack, but a real whole foods meal) with an energy content of 400kcal, and reduced the size of your main dishes to 400kcal, chances are that in the first days of the adaptive period, your body, who is obviously still "expecting" the influx of an 800kcal meal, will expend a (on a kcal-out per kcal-in base) larger amount of energy per meal than on your customary 3x800kcal regimen.
Image 3: Mice primed on a fixed feeding schedule exhibit a profound stress response shortly before the next meal would be due (cf. "Eating by the Clock Could Make You Fat")
Do you remember the mouse-study I covered a few weeks ago? The one where the researchers compared the endocrine response of mice on a fixed feeding schedule, similar to the one you probably acquired as a kid - "Honey, stop playing with your cars / dolls it's time for breakfast / lunch / dinner!" - to mice with constant (ad-libitum) access to food? The mice on the scheduled feeding protocol exhibited an anticipatory stress response before each of the scheduled feedings - the scientists interpreted that as a definite sign of the priming effect of fixed feeding schedules, which went hand in hand with higher plasma levels of the "hunger hormone" ghrelin, an increase in fat and a decrease in lean mass gains compared to the control group. Think of these results, the next time your son or daughter "dares" not be hungry "in time".
Yet, despite being creatures of habit, our bodies adapt pretty fast and under the unrealistic (but easy to calculate ;-) assumption that your body adaptively reduced its postprandial energy expenditure in daily -15% or -10% intervals, the beneficial effect of an increased meal frequency would wear out within three or seven days, respectively (cf. figure 2).

Figure 2: Hypothetical (-10% or -15% per day) adaptation in energy-expenditure after switching from a 3x800kcal to a 6x400kcal meal frequency
It is thus no wonder that the 2011 position stand of the International Society of Sports Nutrition comes to the conclusion that based on current evidence "increasing meal frequency does not appear to favorably change body composition in sedentary populations" - and that, despite the fact that an increase in meal frequency "appears to help decrease hunger and improve appetite control"; so that, contrary to what you will read over and over on health and fitness related publications on the Internet, the bookshelves and at the newspaper kiosk, "in the long term, an increased meal frequency does not appear to significantly enhance diet induced thermogenesis, total energy expenditure or resting metabolic rate" (Bounty. 2011).

But, if increasing meal frequency does not have an effect, wouldn't decreasing meal frequency, as in intermittent fasting, then be as futile? Or does decreasing meal frequency from 5-6 small meals a day to a single gorgeous feast even predispose to obesity, as you may have heard it on CNN only yesterday? How much fat would you gain if, for example, after an intermittent fast, you consumed a 19 cups of pasta à 750g carbs as a post-workout meal (feel free to make suggestions in the comments area ;-)? If you are interested in the answer to this question and many other questions, make sure to come back tomorrow and in the weeks to come for the next more pervasive parts of the Intermittent Thoughts on Intermittent Fasting series on the SuppVersity.