Intermittent fasting and bodybuilding: How to Reconcile Them

Intermittent fasting and bodybuilding: How to Reconcile Them

Intermittent fasting and bodybuilding are compatible and potentially beneficial, but there is a rule to follow.

Gaining muscle, losing body fat is not only a benefit to the silhouette, but also to overall health, whether it is to prevent metabolic diseases or bone fractures. To achieve this, diet and exercise are often combined. Intermittent fasting seduces more and more; For its part, bodybuilding is becoming more and more popular, and not only among teenagers and young people looking to expand. But what happens when we combine fasting and bodybuilding?

Bodybuilding + fasting: yes, but …

In a recent study (2017), American researchers at the University of Texas compared for 8 weeks two groups invited to practice bodybuilding 3 times a week: one followed a classic diet, the other a form of fasting intermittent which consisted of rest days to feed only during a “window” of four hours, to choose between 16 hours and midnight, without limitation of calories.

Results: intermittent fasting resulted in lower calorie consumption compared to the normal feeding group, but without loss of muscle strength. Better yet, among the practitioners of intermittent fasting, the muscle strength and endurance of the lower limbs has increased more than in the other group; ditto for the endurance of the muscles of the upper body.

In contrast, their muscle mass dropped slightly (-200 grams), while participants in the “normal diet” group gained 2.5 kilos of muscle on average. A more detailed analysis reveals that this difference is due to a lower protein consumption: 1 gram per kilogram of weight in the “fasting” group but 1.4 gram in the “normal diet” group.

In another older study (2007), intermittent fasting of the same type (4 hours of feeding per day) combined with bodybuilding exercises led to fat gains compared to a normal diet. In addition, muscle mass increased more during intermittent fasting (+ 1.5 kilograms). In this study, protein requirements seemed better covered than in the 2017 study.

In practice

Bodybuilding and intermittent fasting are compatible, but to gain weight, you need to be careful about protein intake. Protein requirements when spontaneous calorie consumption decreases, including bodybuilding, are probably between 1.3 and 1.8 grams per kilogram of body weight, and perhaps even above.



Tinsley GM, Forsse JS, Butler NK, Paoli A, Bane AA, La Bounty PM, Morgan GB, Grandjean PW. Time-restricted feeding in young men performing resistance training: A randomized controlled trial. Eur J Sport Sci. 2017 Mar;17(2):200-207.

Stote, K. S., Baer, D. J., Spears, K., Paul, D. R., Harris, G. K., Rumpler, W. V., Mattson, M. P. (2007). A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults. The American Journal of Clinical Nutrition, 85(4), 981–988.

Phillips, S. M. (2014). A brief review of higher dietary protein diets in weight loss: A focus on athletes. Sports Medicine (Auckland, N.Z.), 44(Suppl. 2), 149–153.

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