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)
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
- 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
|Image 2: Never (!) let the scale put a spanner in your day. Use progress pics and a caliper instead.
|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)
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.
Although, I cannot divine your thoughts, I suspect that your questions, just like mine, will fall into one of the following three broad categories:
- Can intermittent fasting help me lose body fat?
- What effects will intermittent fasting have on my overall metabolic health?
- Is intermittent fasting a suitable diet strategy for (recreational) athletes in phases where they are looking to gain weight and/or improve their performance?
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")
|Figure 2: Hypothetical (-10% or -15% per day) adaptation in energy-expenditure after switching from a 3x800kcal to a 6x400kcal meal frequency
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.