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| Image 1: It stands to reason that "reducing" your food intake to one serving of 13,780 pounds of spaghetti + 120 gallons of ruby red marinara sauce is not really what "intermittent fasting" is all about (world record of 2009 at Buca di Beppo's in Garden Grove). |
In yesterday's first installment of the
Intermittent Thoughts on Intermittent Fasting series,
you have already learned that the idea of increasing energy expenditure and improving weight loss by increasing the number and decreasing the size of your meals is futile, because, in the longer term (>1 week), any temporarily occurring metabolic overshoot, i.e. an inappropriately (as in larger than "optimal") pronounced postprandial thermogenic response, will be leveled out by metabolic adaptation processes. This does yet not automatically exclude that the reverse, i.e. an appropriate increase in postprandial energy expenditure, would occur whenever someone, who has been eating 3-4x more or less balanced meals since he/she was a child, out of a sudden decided that it would be prudent to skip 2 or 3 of his meals and to cram his/ her whole caloric intake into 1 or 2 gorgeous meals.
So, 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?
"Intuitively", yet not as in genetically programmed, but rather as a result of lifelong medial and educational indoctrination, it occurs to us only reasonable that someone, who crammed his/her whole daily calorie intake of 2.400kcal into a single meal, when his/her body is used to 3x or 4x 600-800kcal servings, would gain (fat)weight - especially if there are some of those nasty fattening carbs around the "new smarter(?) generation" of dietitians has finally identified as the root of all metabolic disease. Accordingly, you will probably not be surprised by a remark I took from a review of the effects of meal frequency on weight gain and body composition by Bellisle et al. from the year 1997 (Bellisle. 1997)...
[A] very large bolus meal with a high carbohydrate content might saturate the maximal rate of glycogen synthesis and force additional disposal via de novo lipogenesis; there is much evidence to support a hyperlipogenic effect of gorging in animal studies.
Now, while intermittent fasting obviously allows for several smaller meals within a 4-8h time window, it seems logical that the "saturation" of glycogen synthesis could nevertheless become a problem. After all, you have read about the limited ability of our bodies to "store away" excess glycogen in previous posts on the SuppVersity and will thus be familiar with the idea that, contrary to the fat storage capacity of our adipose tissue, our bodies' glucose stores, which are located primarily in muscle and liver tissue, are very limited.
"How much fat can you really gain from a single 750g carbohydrate meal?"*
* this is the answer to the question at the end of yesterday's installment of the Intermittent Thoughts on Intermittent Fasting series
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| Illustration
1: This is a very theoretical calcuation of
what "could" happen if you ate 19 cups of cooked pasta = 750g of carbs after a glycogen depleting workout (calculations based on estimates by Acheson. 1988) |
While you may have expected that the "exact" amount of carbs your body
would be able to store varies with the amount of muscle you are
carrying, it may surprise you that it also varies according to which
source you are using (that's science, folks!). It is, however in general
assumed that an average adult human being
can store about 500grams of carbohydrate. Athletes on the other hand could theoretically store up to 1.0-1.1kg before
the onset of de novo lipogenesis, i.e. the synthesis of fatty acids from
carbohydrate substrates (
Acheson. 1988).
In 1988, Acheson et al. established in a series of overfeeding studies that it takes roughly 475grams of excess carbohydrates to manufacture and store 150grams of fat (Acheson. 1988).
You may notice that this would yield an energetic ratio of 1g of fat to 3g of carbs and thus constitutes another violation of the
generally accepted oversimplified "laws of dietary thermodynamics", as
they are propagated by dietitians and mainstream-media. If our bodies
could inter-convert and store macronutrients as readily as people are
made to believe, according to the 4kcal/9kcal energy rule, the
750g of carbs in my sample calculation in illustration 1 should translate into 111g of fat, if 500g of the carbs had previously been stored in empty glycogen stores.
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| Image 2: R. Feinman (photo) and Eugene Fines authored a paper on the fallacy of the "a calorie is a calorie"hypothesis |
If you are interested in a
detailed discussion of the applicability of the laws of thermodynamics in a nutritional context, I suggest you start by reading Richard Feinman and Eugene Fine's 2004 paper
"A calorie is a calorie" violates the second law of thermodynamics, where the two scientists discuss existent data to show that thermogenesis, alone, would be sufficient to predict
metabolic a metabolic advantage of low- over high-carb diets and make a point in stating that "as a general principle, 'a calorie is a
calorie' violates the second law of thermodynamics."
(Un-?)fortunately,
neither carbs nor fats are built of "calories" that your body could use interchangeably and without any additional effort,
so that the real world outcome of overeating is a lot more complicated
than basic "carbs in vs. carbs out times 4/9" calculations - even if one
discards the influence of other macro- and micro-nutrients and the temporary
+35% increase in energy expenditure Acheson et al. observed in their low-fat, high-carb overfeeding studies (~4.500kcal/day).
Yet, before we are delving any deeper into a discussion of optimal macronutrient composition for lean gains, weight loss and optimal performance (we will get to that in a later part of this series, I promise), let's get back to the topic at hand and look at some of the research that may be able to explain, why anecdotal evidence clearly shows that, on a combined exercise +
intermittent fasting regimen, as Martin Berkhan and others recommend it, weight
gain never seems to become an issue - and that despite the fact that many of his followers claim they even had to force themselves to eat the prescribed amount of food.
Myth 2: A lower meal frequency equals (fat)weight gain
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| Illustration 2: Comparison of feeding schedules on "normal diet", alternate-day-fasting (ADF) and the current interpretation of intermittent fasting (IF). |
Quite often, when you find explanations on why intermittent fasting would or not, the authors cite studies which employed
alternate-day-fasting (ADF) regimens. It stands out of question that alternately eating a normal diet on one day and refraining from food consumption on the following day is a form of "intermittent fasting" - nevertheless a better and even more studied
"model" (this is just our perspective on these studies)
of non-calorically restricted intermittent fasting comes from the
middle-east, where the effects of
Ramadan fasting, which prohibits any food intake before sundown, have been studied for decades,
now.
Although the small breakfast most of the Muslims ingest before
dawn and the additional abstinence of fluid intake distinguishes Ramadan
from
intermittent fasting, the
average period dieters remain without
food (from 4am to 7pm, i.e. 15h) is comparable and, what's equally important, the length of the
fasting and thus the study period (one month) is
long enough to bring about measurable
effects.
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| Image 3: After ~13h of fasting 78% of your liver glycogen stores of roughly 300mmol/kg liver tissue will be depleted; 3h left until your body will have to come up with "alternative" fuel sources. |
Those of you who read the erratum on the "
Glycogen-Free Muscle Growth" post a few days ago, will already be familiar with a possible explanation for the success many people have with the 16h fasting-window Berkhan and others suggest mainly based on a very practical "no muscle loss observed" argumentation (cf.
Berkhan. 2010). The latter is related to the capacity and usage of your hepatic and muscular glycogen stores. While your
muscle glycogen stores are "degraded to generate ATP
during increased energy demand", your
liver glycogen stores function as an
immediate back-up system for whole body glycogen supply (
Greenberg. 2006). Thus, it appears obvious that your body will have to
catabolize more protein and liberate and oxidize more fat by ramping up its glucocorticoid output, as you approach the ~16,67h fasting limit, when the 300mmol/kg glycogen your liver holds in the fed state will be depleted (calculations based on a hourly glycogen depletion of 18mmol/kg as it was observed by
Nilsson. 1973). Although, I will address this issue in more detail in a future installment of this series, it is also important to understand a
major and potentially significant difference between "intermittent fasting" and "alternate day fasting", where the complete depletion of hepatic glycogen stores, as well as the consequent stressful switch to alternative fuel sources, the gradual progression into a catabolic state and the ensuing cortisol-related suppression of thyroid hormones and androgens are inevitable consequence (even if you lie in bed all day) of the extended (24h) fasting period and thus pave the way to what I described as "starvation mode" in the introduction of
part I of this series.
One of the most recent Ramadan studies published in the
Asian Journal of Sports and Medicine was conducted by Khaled Trabelsi and four colleagues of his from Tunesia, New Zealand and the US (
Trabelsi. 2011). Its topicality aside, the study is also interesting because the
subjects, 10 men at an average age of 26.6 years and with a BMI: 24.6kg/m² and a body
fat percentage of ~19.4%, who exercised at least 3x a week, are somewhat representative of many men out there who
may be considering to experiment with intermittent fasting, these days.
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| Figure 1: Changes in energy intake during
and body composition in the course of Ramadan fasting in 10 healthy
physically active (min. 3x/week) men (data calculated based on Trabelsi. 2011) |
As the data in figure 3 goes to show, daytime fasting
and the reduced meal frequency induced a
voluntary -7% decrease in energy
intake, which went hand in hand with a +6.6% increase in protein intake
and brought about a slight, yet statistically significant recomposition
effect, i.e. the
loss of 2.6% body fat (measured by the means of a caliper) without concomitant reductions in lean body mass.
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| Image 4: The
beneficial macronutrient modulation (+6.6% protein; less carbs and fats)
the subjects from the Trabelsi study unconsciously adapted during
Ramadan are probably the result of family traditions and not some sort
of instinctive dietary adaptation (at least not in the short run) |
In view of the fact that the voluntary, or I should
say,
unconscious increase in protein intake at the expense of dietary
fats and carbohydrates has lately been deemed particularly beneficial in terms
of losing fat and maintaining muscle weight (more on
optimal macronutrient composition during intermittent fasts in a future installment of this series), it could appear as if the fasting Muslims intuitively knew about the benefits of additional amino acids! Unfortunately, the
underlying reason for the increase in protein intake is probably way more profane. During Ramadan you
do not snack,
you abstain from the classic sweet breakfast, and all the other low
protein foods. Instead, you have one or two large high quality (and in
the Arabic world this still involves a healthy peace of meat) meals with
your family.
When we are looking for the underlying
reasons for these beneficial changes in body composition a 2005 study by
Heilbronn et al. from the
Pennington Biomedical Research Center comes to mind (
Heilbronn. 2005). In their study 16
non-obese health men (N=8; age 34y; BMI 25.2; fat 22%) and women (N=8; 30y; BMI 22.6; fat 25%) who fasted
every other day
lost 4% body fat and 2.5% of their body weight within 22 days. And
despite the fact that this is not the kind of intermittent fast that got
Duong his "
Aesthetically Muscled" physique (cf. my remarks on the role of liver glycogen stores and the 16h fasting window in one of the red info-boxes above), the
subjects did not experience the dreaded decrease in resting metabolic rate (RMR)
that is so commonly seen on traditional diets with a constantly reduced calorie intake.
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| Figure 2: Effects of 22 days of alternate day fasting (ADF) on body composition (lean mass and fat mass in kg) in 16 non-obese, healthy subjects (data adapted from Heilbronn. 2005) |
The Heilbronn study,
also provides a first glimpse at one of the topics of the future
installments of this series, which is the underlying mechanism by which
alternative fasting could facilitate such results: a major factor probably was
the -57% decrease in fasting insulin that allowed for a greater
release of stored fatty acids and thus facilitated the +15 g/day
increase in fat oxidation - energy which had not to be derived from the oxidation of valuable muscle (or other organ) proteins. In view of what I have said about the differences between intermittent and alternative day fasting (cf. red box), it is yet noteworthy that
the subjects in the Heilbronn study did lose 1.1% of their lean mass, while the fasting Muslims in the Trabelsi study despite performing their habitual 3-times a week exercise regimen, in a fasted state between 4pm
and 6pm, i.e. ~12-14h after their last and shortly prior to their next
meal, maintained (+0.2% is a non-significant increase) their lean body mass. This goes to show your that exercise although it may not mandatory to avoid weight gain and derive benefits from an intermittent or alternate-day fast that is characterized by a reduced meal frequency and an increase in meal size, can help maintain (with appropriate meal-timing and supplementation as discussed in future installments of this series, maybe even build) lean body mass.
A pros pos exercise, interestingly,
none of the 10 subjects who were obviously not used to exercising in the fasted state reported any changes in the rate of perceived exertion. This obviously contradicts observations the anti-fasting faction on the Internet commonly
cites as one of the most important reasons not to go on an intermittent
fast, for everyone for whom his/her exercise (and some even say cognitive) performance is important. In view of the fact, that,
even for me, there is a life beyond the SuppVersity, I will yet have to postpone myth #3, i.e. "Intermittent Fasting Will Ruin Your Physical and Cognitive Performance" to the next installment of the
Intermittent Thoughts on Intermittent Fasting series. In the mean time, feel free to leave comments, questions and suggestions as to where this series should be heading on
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