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There is a big fasting boom on the internet, but it is hard to sift through the claims of fitness and health bloggers and the real evidence.

I have spent hours reading studies on fasting - it is obvious many have concluded that various forms of fasting actually do induce several health benefits such as increased human growth hormone production, augmented metabolic regulation of Sirtuins (that may play a role in decreased carcinogenesis and slower ageing), increased neural autophagy, increased neural cell growth, increased lifespan and others.

While this sounds amazing and more human studies are needed, I wonder if anybody knows if we can already infer from the evidence we have an optimal feeding pattern for humans?

I feel (I am not sure exactly) that the 16:8 intermittent fasting pattern (16 hours fasting and 8 hours of feeing time daily) has had some research done on it, but yet again, mostly non-scientists propagate the idea. I am looking less for other/new evidence of fasting's health benefits, but rather for science-backed conclusions. I believe we should be able to gather the evidence and implement it correctly.

I wonder about this because who wouldn't want to know how to eat in a way that would prolong our lifespan and have other health benefits?

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Quality of Evidence First off, I'd be careful with the sources you are citing-- one of them is an opinion letter in a journal, and two are studies in rats.

When looking at studies, the best evidence is that with patient-centered outcomes (5). Increased dentate gyrus neurogenesis or HGH production are interesting results, but it's unclear that those translate into meaningful benefits for you. The papers that are worth changing your daily habits for are the ones that look at endpoints that are meaningful to you: weight loss, increased survival, improved memory, etc. While you can theorize a link between neurogenesis or HGH and a meaningful outcome, science is full of theoretical connections that turned out not to exist in real life.

Evidence for Intermittent Fasting In Humans There is not yet great evidence on the topic, as you mentioned, but there is a decent review published in 2014 comparing calorie restriction (CR) diets with intermittent fasting or alternate day fasting (IF/ADF) diets. It concludes (emphasis mine):

Results reveal superior decreases in body weight by CR vs IF/ADF regimens, yet comparable reductions in visceral fat mass, fasting insulin, and insulin resistance. None of the interventions produced clinically meaningful reductions in glucose concentrations. Taken together, these preliminary findings show promise for the use of IF and ADF as alternatives to CR for weight loss and type 2 diabetes risk reduction in overweight and obese populations, but more research is required before solid conclusions can be reached.

So while intermittent fasting may not cause as much weight loss as a typical diet, it seems to be similarly good at eliminating fat.

There are several studies out there that look at intermittent fasting and weight loss, but they all have small sample sizes (n<110) and most of them involve women only, so it's hard to extrapolate much from them. However most of them say that the two dietary approaches seem to be similar in terms of weight loss (2-4).

Overall, it looks like intermittent fasting has comparable effects on weight and blood sugar as traditional calorie-restrictive diets.

References:

Review of Intermittent Fasting Effects on Diabetes and Weight Loss

Year Long Weight Loss In Overweight Women

Intermittent Fasting and Weight Loss In Obese Women

Intermittent vs. Calorie Restriction Diets in Young Overweight Women

Patient-Centered Outcomes

  • Thank you very much for your answer Nate! 1.) My bad, I cited quickly some studies, but I could have found better ones. 2.) Personally, I am not at all concerned about weight since I am slim with very low body fat - I am mostly concerned about ageing. I would do anything that is "healthy" (prolonging lifespan, better immune response, slower ageing, higher resistance to carcinogenesis) and in my power. Hence, I wanted to know if we already can infer something from the evidence we have. I already eat healthily, yet if the time pattern helps in such an amazing way, I'd change it too. – Fipah Jan 25 '18 at 23:41
  • @Fipah Unfortunately studies on longevity and ageing take a VERY long time (since you might not notice an effect for decades). The same goes for rates of cancer growth. Trying to infer from incomplete evidence is very tempting, and people do it all the time. The majority of the time, though, all the tantalizing connections people come up with turn out to be incorrect. A big part of diet and health more broadly is how you feel-- I'd say if an intermittent fasting diet makes you feel good, do it. You're not likely to find conclusive evidence on the topic for decades, if ever. – Nate Jan 26 '18 at 22:38
  • Thanks for your comment @Nate! I was thinking maybe quicker studies on mice and rats might allow us to extrapolate because they have shown promising evidence, yet I understand - we are not mice nor rats and studies on humans will take long. // I feel good both ways (eating meals throughout the day or eating in an 8 hour window only) since I feel good and I am healthy in general - I'd just want to do what is "healthier" for me on the level I cannot directly feel, say if such and such way of eating reduces telomere shortening I think I would not be able to directly sense it. – Fipah Jan 27 '18 at 11:00

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