The Truth about Intermittent Fasting and Weight Loss

Intermittent fasting (IF) is all the rage right now, with all sorts of “experts” and “gurus” waxing rhapsodic about the plethora of benefits that can be had when restricting your food consumption to a few hours each day.

Today, we’re blowing past all of the hype, hoopla, and high-praise of self-induced starvation to see what science actually has to say regarding whether or not intermittent fasting is the golden goose of weight loss.

Intermittent Fasting for Weight Loss

A recent systematic review and meta-analysis comparing intermittent fasting to traditional dieting (daily calorie restriction) found no differences in fat loss. Researchers also documented similar improvements in metabolic markers of health between individuals who chose to fast vs those who followed the standard method for weight loss (eating less each day than normal).[1]

Other popular fasting protocols, such as the 5:2 diet where you eat “normally” for 5 days and eat next to nothing for two days of the week, have been compared to continuous calorie restriction in subsequent studies and again, intermittent fasting was found to be as effective as continuous calorie restriction, but NOT superior.[2,3]

In the longest randomized-control trial to date (12 months total) that compared the “5:2” intermittent fasting (IF) model (including 2 non-consecutive fasting days per week) with daily caloric restriction, researchers concluded:

“Both intermittent and continuous energy restriction resulted in similar weight loss, maintenance and improvements in cardiovascular risk factors after one year. However, feelings of hunger may be more pronounced during intermittent energy restriction.”[3]

Weight loss ultimately boils down to calories in versus calories out. Anything that helps reduce the amount of food you eat daily or increases the amount of energy you burn (i.e. exercise), inherently supports fat loss.

Intermittent fasting can be effective for fat loss if it helps you stick to your calorie limits each day, but you can get the exact same weight loss results (and potentially less feelings of hunger) by dieting the “traditional way”.

Unfortunately, intermittent fasting zealots are wrong...IF is not better for fat loss or muscle growth. It can work, but it’s not magical by any means.

References

1. Harris, L., Hamilton, S., Azevedo, L. B., Olajide, J., De Brún, C., Waller, G., … Ells, L. (2018). Intermittent fasting interventions for treatment of overweight and obesity in adults:  a systematic review and meta-analysis. JBI Database of Systematic Reviews and Implementation Reports, 16(2).
2. Schubel, R., Nattenmuller, J., Sookthai, D., Nonnenmacher, T., Graf, M. E., Riedl, L., … Kuhn, T. (2018). Effects of intermittent and continuous calorie restriction on body weight and metabolism over 50 wk: a randomized controlled trial. The American Journal of Clinical Nutrition, 108(5), 933–945. https://doi.org/10.1093/ajcn/nqy196
3. Sundfør, T. M., Svendsen, M., & Tonstad, S. (2018). Effect of intermittent versus continuous energy restriction on weight loss, maintenance and cardiometabolic risk: A randomized 1-year trial. Nutrition, Metabolism and Cardiovascular Diseases, 28(7), 698–706. https://doi.org/10.1016/j.numecd.2018.03.009