termittent Fasting Diet - a Critical Review
Intermittent Fasting (IF) … Personally I find it as one of the most surprising dietary trends nowadays . First thought that comes to my mind is “this cannot work, since it’s so much against diets proven most effective”. However I have read few logs of people I know personally trying it on themselves, including well known dietician John Berardi (whom I do not know personally). And surprisingly it works… to a degree.
I.F. is a type of diet where the time of food consumption per day is set up to a relatively short period of few continuous hours. It is believed that the human kind evolved eating big meals only after many hours of fasting. Proves are purely historical and basing on so called “survival science“.
In this review I am not going to condemn fasting as such. Perhaps it’s worth recommending to some people.
All the paragraphs in this review will be referenced to “feeding” protocols I have found most effective and healthy in sports/fitness industry, namely:
-Low Carb Diet (L.C.), or
-Paleo Diet,
-Structural Refeeds.
In my opinion this comparison is going right to the core of the I.F.’s surprising, but not “jaw-dropping” results.
BTW… and of course this review would be far too long if I tried to thoroughly analyze all the aspects such eating patterns. i.e. all kinds of I.F. or digestion speed.
I have written it 5 times, every one was too long.
There is a severe scarcity of research done on IF in human population. And as long as no industry is actually interested in your eating or fasting hours, it will take time before more researchers find money to finance a scientific study thoroughly examining this phenomenon. Lack of such give inspiration to “urban legend writers“, “myth busters”, and clever marketing of I.F. books, websites, PT services, courses and so on.
Example:
“Alternate-day fasting in non obese subjects: effects on body weight, body composition, and energy metabolism”
-22 days period
-bodyweight down -2.5%
-body fat -4%
http://www.ajcn.org/...1/1/69.abstract
Research FAULTS ? Perhaps not strictly faults, but I wish that those studies had a Low
Carb control group. At least a group that ingests carbohydrates at the same times of the day as the IF groups. This would be the clearest proof of superiority, that needs no independent cross-references to other diets. Another wish-list point would be having those people do strength training.
MECHANISMS of I.F. confronted with more proven L.C. Diets.
*I am not going to quote corresponding research on L.C. , since the tests I.F. vs. L.C. should have been run simultaneously. Of course I assumed we have a sufficient base of knowledge of the mechanisms behind L.C.
-insulin sensitivity in I.F. vs. L.C. Diets:
“Effect of intermittent fasting and refeeding on insulin action in healthy men
[…] This experiment is the first in humans to show that intermittent fasting increases insulin-mediated glucose uptake rates, and the findings are compatible with the thrifty gene concept. “
http://jap.physiolog...6/2128.abstract
-Again if I were looking for FAULTS, I would have a L.C. control group with carbohydrate refeeding as frequent as the I.F. group.
-The acctual foods or macronutrient ratios in all I.F. diets used in studies are… missing.
-Any diet with lowered insulin levels for a period LONG ENOUGH to reset insulin receptors, would increase insulin sensitivity.
-Insulin management is CRUCIAL for anybody who aspires to get optimal body composition. I.F. diets do not seem to emphasise on omega-3 fatty acids, or anything else that could possibly increase insulin sensitivity, like foods encouraged in Paleo Diet.
-Growth Hormone
-I have not found research on I.F. concerning this important lypolytic hormone, but as we know it’s secretion is inversely proportionate to insulin levels. We could assume the level of GH is similar in both diet types, but not after considering that it’s secreted in “pulses” and more frequent big protein & fat meals (L.C.) are increasing it’s level few times throughout the day.
-Cortisol management in I.F. vs. L.C. Diets.
“A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults.
However, when consuming 1 meal/d, subjects had a significant increase in hunger; a significant modification of body composition, including reductions in fat mass; […] and a significant decrease in concentrations of cortisol.”
http://www.ncbi.nlm....pubmed/17413096
-Decreased cortisol response might be a result of less frequent ingestion of inflammatory foods like gluten sources or chemical food additives. Another explanation might be reduced food sensitivity. Those suggestions need to be confirmed by more research on I.F.
-It has been previously examined, that Paleo Diet, if done correctly, prevents food sensitivities and lowers overall cortisol levels.
-During the fasting time, glucagon is not the only catabolic hormone that helps with blood sugar level maintenance. Cortisol is secreted to help with breaking down active metabolic tissue i.e. muscle , in order to reduce glucose requirements. This is unlikely to happen with higher meal “Paleo” frequency, but still possible with regular Western diet consisting of 3 meals a day.
Leptin Management, fat loss set point:
As we know Leptin levels decrease by about 50% in 7 days without carbohydrates. Typical IF diet is “eating whatever”, but more educated approach means eating Low Carb during those few hours of feasting, and loading carbs with frequency depending on body fat percentage.
Some people actually do it and still the results are slow. I am guessing that such a low meal frequency simply slows down metabolism despite leptin-boosting structural refeeds, alternatively I.F. switches on some fat-protective systems yet to be confirmed in more sophisticated groups of I.F. participants.
A fine example here is Mr Martin Berkhan, who promotes I.F. system called “lean gains”, and claims that the single digit body fat percentage may take years to reduce.
http://www.leangains...-point-and.html
Not the quickest way at all !
Same problem was encountered by Dr John Berardi, .
Gluconeogenesis in I.F. vs. L.C. Diets
Contributions of gluconeogenesis to glucose production in the fasted state.
“The contribution of gluconeogenesis to glucose production was 47 +/- 49% after 14 h, 67 +/- 41% after 22 h, and 93 +/- 2% after 42 h of fasting. “
http://www.ncbi.nlm....8?dopt=Abstract
Take away point: we DO break down proteins as we break down fats exactly the same way as on Low Carb Diet (LC) with more frequent meals throughout the day. The difference is:
-on LC we don’t need to cannibalise own proteins most of the time.
-on LC we deliver enough essential fats to keep some important metabolic pathways active all day long
-conclusion: on LC we get at least the same fat burning speed , but less likely lean mass loses when doing L.C. diet. Lesser Evil is a Bigger Good.
It is well worth mentioning that eating 3 TYPICAL meals vs. one meal with the same calorie intake, makes the IF win:
Fatty Acid Oxidation
-increased fatty acid oxidation capacity, while fasting:
http://www.ncbi.nlm....pubmed/12051710
-LC diet should give similar effect, without risk of metabolism slowing down.
“In conclusion, this study shows that, even early in the phase of the postabsorptive period when liver glycogen stores are maximal, gluconeogenesis contributes approximately 50% to hepatic glucose production.”
http://ajpendo.physi...1/E186.abstract
-It means that we have nearly the same gluconeogenesis BOTH just after meal, and when we wake up in the morning.
-A major fault of all those researches would be lack of data on corresponding metabolic speed in comparison to certain “fuel types” contribution.
-In LC Diets we have similar fat burning rates and metabolic pathways active , but more frequent protein and fats ingestion keeps the metabolism much faster.
-WHO SHOULD TRY IT?
“These findings suggest that these diets are equally as effective in decreasing body weight and fat mass, although intermittent CR may be more effective for the retention of lean mass.”
http://www.ncbi.nlm....5?dopt=Abstract
According to research and common sense - everybody who feels uncomfortable with other types of diet, who is too stressed about necessity of eating at given (BUSY) times.
From all the above scientific references, and witnessing others trying it, I can recommend it as superior to 3 meals a day, provided the total amount of calories are sufficient.
FINAL WORDS - HAVE NO DOUBTS
* I guess any level of education is sufficient to understand this reasoning:
The best example of Intermittent Fasting in real life, one I consider MOST impressive… impressive for a I.F. of course:
“Over the course of six months, I dropped twenty pounds of weight, from 190 pounds to 170 pounds. I also reduced my body fat from 10% to 4% while maintaining most of my lean muscle mass. ”
-Dr John Berardi
http://www.precision...fasting/summary
NOT SO IMPRESSIVE, this guy looks after bodybuilders and has similar results with them and himself in the past within weeks. NEVER as long as 6 months.
Martin Berkham dropped single digits of body fat percentage through years of practising I.F.
If you want best results, and time is a factor, there are other, better diets for you.
Daff
Krzysztof Piekarz
jabolcokk
King_Odin
Bestniak
Hekade
