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Health Benefits Of Fasting?

sharma-obesity-fat-dietingEven a cursory glance at popular media stories on diets and weight loss will lead you to countless posts on the supposed benefits of alternative-day, intermittent or other forms of fasting.

But just how much evidence is there that any of this is actually beneficial to your health (i.e. if you are not a mouse).

This question was addressed by Benjamin Horne and colleagues from Salt Lake City, Utah, in a paper published in the American Journal of Clinical Nutrition.

The researchers review the evidence on various forms of fasting from the published literature, which consists of a grand total of three randomised controlled trials, together involving about 100 participants, with durations ranging between 2 days to 12 weeks.

Although all three trials reported some benefits in terms of body weight, cholesterol and other surrogate markers, the authors failed to find any study that looked at actual clinical endpoints (e.g., diabetes or coronary artery disease].

To be fair the authors did find two observational studies in humans (both involving the first author of this study), where fasting was associated with a lower prevalence of heart disease or diabetes but, as readers should be well aware, these types of studies cannot prove causality.

I guess it would be fair to say that the popular enthusiasm about the health benefits of various forms of fasting, as far as their benefits for humans are considered, appear largely based on hope and hype – at least as far as clinically meaningful outcomes are concerned.

This is not to say that fasting, whether alternative day or otherwise, may not well have some medical benefits – fact is, we just don’t know.

Or rather, as the authors put it,

“whether fasting actually causes improvements in metabolic health, cognitive performance, and cardiovascular outcomes over the long term; how much fasting is actually beneficial; and where the threshold of hormesis resides (i.e., a balance between long-term benefit from fasting compared with harm from insufficient caloric intake) remain open questions….considerable additional clinical research of fasting is required before contemplating changes to dietary guidelines or practice.”

Vancouver, BC


  1. Dr Sharma,

    I am on the cusp of PreDiabetes and I have PCOS. I have maintained the majority of my 70 lb loss for most of 16 months. Different forms of Intermittent Fasting had been a tool for me. I have tried eating windows, 34 hour fasting, dry fasting, 1 meal a day diet etc, Alternate Day Fasting, etc. intermittent Fasting lowers my Insulin Levels and cravings when practiced right especially ADF combined with a 3-5 hour eating window daily. When I was doing that, it lowered my appetite so much sometimes I found it harder to decide what even sounded good. This is HUGE in maintaining a large loss. If the appetite is lowered and we don’t have to think about food as often Intermittent Fasting could make it easier for people to lose and Maintain weight. Intermittent Fasting can Simplify things a lot instead of trying to stay in an eating plan 3-6 times a day eating 365 days a year, you potentially don’t need to make as many eating decisions.

    So yes many many positive benefits of fasting in the Study of One.

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  2. It is true that people overstate the benefits of fasting based on insufficient evidence. It is also true that it is unlikely that any long-term randomized controlled trials will ever be done that prove any benefits of this or other ways of eating. There should be more studies on the different forms of intermittent fasting to confirm things like the effects on shorter term markers, especially if the effects of fasting can be teased away from the effects weight loss. In the meantime, I’ll keep fasting 2-3 times a week and maintaining my 50lb+ weight loss.

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