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Intermittent Fasting: No Evidence of Enhanced Weight Loss

I recently wrote about why—theoretically—intermittent fasting (or alternate day fasting) actually has little likelihood of enhancing weight loss, over other forms of calorie restriction. (See: Alternate Day & Intermittent Fasting: Magic for Weight Loss or Just Another Fad?)

Today’s blog assesses the research that has specifically compared any kind of fasting regime (intermittent-calorie-restriction) to the typical dieting approach (constant-calorie-restriction) on weight loss.

While there are multiple studies of intermittent fasting in the literature most have not looked at weight loss as an outcome (most are studying biomarkers of cardiovascular disease or longevity), and many have no control or comparison group. So, we have only three studies in the published literature that have actually compared weight loss between constant-calorie-restriction and intermittent-calorie-restriction groups.[i],[ii],[iii]

In all three studies the outcome was the same: No significant differences in weight loss, or changes in body composition.

The Bottom Line: Intermittent Fasting isn’t a magic bullet for weight loss. Granted (as long as overall calorie-restriction is equal), it is just as effective as other approaches to calorie restriction. Fair enough, however, there’s no data on anyone using Intermittent Fasting for weight maintenance.

If you are considering trying intermittent fasting, I suggest the following questions:

  1. Will Intermittent Fasting be easier to follow than other forms of calorie restriction for me, and why?
  2. Can I see myself using this as permanent lifestyle change?
  3. If not, how do I propose to maintain my weight loss?

There's an endless number of wackadoodle diets out there, and they mostly work—for as long as you are able to follow them. In the long run however, permanent lifestyle changes are needed in order to maintain one's weight loss. That's why I advocate beginning with the end in mind. If you approach weight loss as a lifestyle change you will essentially be practicing the same behaviors (needed for weight maintenance) during the period you are losing weight. It's boring, it's not new, but it is realistic.

All the Best!

PS--if you like this blog you may also like my book: The NEW Healthy Eating & Weight Management Guide.

i] Harvie MN, et al. The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: a randomized trial in young overweight women. Int J Obes 2011;35(5):714-727.

[ii] Hill JO, et al. Evaluation of an alternating-calorie diet with and without exercise in the treatment of obesity. Am J Clin Nutr 1989;50:248-254.

[iii] Arguin H, Dionne IJ, et al. Short- and long-term effects of continuous versus intermittent restrictive diet approaches on body composition and the metabolic profile in overweight and obese postmenopausal women: a pilot study. Menopause. 2012 Aug;19(8):870-6.


Reader Comments (1)

Great post with an excellent point. I recommend IF as an option and find a select few are drawn to it and can use it successfully for long periods. Others are turned off at the sound of "going long periods without eating" and that's okay too.

I'd love to see some research investigating connections between the type of dietary style a person finds success with and other personality traits (psych stuff). It seems people who respond to IF have a pretty good handle on the eat to live perspective which is often a result of them being driven in other areas of their lives.

One more thing... did you see the IF study by Klempel in Nutrition Journal 2012? Compared IF with or without liquid meal replacement... another win for MRPs as far as short term effectiveness is concerned.

Keep up the good work!

April 13, 2013 | Unregistered CommenterMatt

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