Effects of High Protein Diets on Body Composition

Protein is the most important macronutrient for positive alterations in body composition. Previous work has suggested that protein intakes in the range of 1.2-2.0 grams per kilogram (kg) body weight per day (g/kg/d) are needed in active individuals. In contrast, the Australians recommended daily allowance (RDA) for protein is about 0.8 g/kg/d. This is inadequate for athletes or active individuals who engage in exercise/sport training for several hours per week. Nonetheless, consuming more than the RDA may be considered a ‘high’ intake of protein. According to the Position Stand by the International Society of Sports Nutrition, intakes of 1.4-2.0 g/kg/d are needed for physically active individuals. They suggest that a ‘high’ protein intake is anything that exceeds 2.0 g/kg/d. However, little had been known regarding the effects of protein intake exceeding 2.0 g/kg/d.

It hadn’t been clear if protein overfeeding resulted in body fat gains. Certainly, overfeeding in general will promote body weight and fat mass gain. Two weeks of overfeeding on candy versus peanuts showed that waist circumference increased only in the candy group despite the identical increase in caloric intake. This suggests that overfeeding on sugar results in body fat gains in contrast to consuming a natural food comprised of unprocessed carbohydrate and fat. Furthermore, there may be no difference in overfeeding on fat or carbohydrate in terms of fat storage. Presently, the effects of protein overfeeding in resistance-trained individuals hadn’t been investigated until now.

Five Times The Recommended Intake

In a recent study done by Antonio and colleagues (2014) for the Journal of the International Society of Sports Nutrition investigated the effects of a high protein diets on body composition in resistance-trained men and women in the absence of changes in training volume.

In this study 40 very experienced resistance-trained subjects volunteered and were unequally randomized to a control or high protein diet group. Individuals in the control group were instructed to maintain the same dietary and training habits over the course of the study. On the other hand, the subjects in the high protein diet group were instructed to consume 4.4 grams of protein equal to 4.4 g/kg/d. Subjects kept a daily diary of their training and food intake to measure consistence and compliance.

The key finding in the present study is that consuming a hypercaloric high protein diet has no effect on body composition in resistance-trained individuals. This is the first investigation in resistance-trained individuals to demonstrate that consuming a high protein hypercaloric diet does not result in a gain in fat mass. On average, they consumed 4.4 g/kg/d of protein which is more than five times the recommended daily allowance.

It should be noted that in previous studies, subjects that consumed a hypocaloric diet that is higher in protein and lower in carbohydrate, experienced more favourable alterations in body composition. However, the effects of consuming extra calories above normal baseline intake coupled with changes in macronutrient content have not been fully elucidated. The current investigation found no changes in body weight, fat mass, or fat free mass in the high protein diet group. This occurred in spite of the fact that they consumed over 800 calories more per day for eight weeks. The high protein group consumed an extra 145 grams of protein daily. This is the highest recorded intake of dietary protein in the scientific literature that I’m are aware of.


The results of the current investigation do not support the notion that consuming protein in excess of purported needs results in a gain in fat mass. Certainly, this dispels the notion that ‘a calorie is just a calorie.’ That is, protein calories in ‘excess’ of requirements are not metabolized by the body in a manner similar to carbohydrate.

One might suggest that the high thermic effect of protein may make it difficult to gain body weight during times of overfeeding. It has been shown that the greater the protein content of a meal, the higher the thermic effect. Both young and old individuals experience an increase in resting energy expenditure after a 60 gram protein meal. Also, the thermogenic response to a mixed meal differs between lean and obese subjects as studies have indicated.

Another factor that may have played a role in the current investigation is the type of protein consumed in the high protein group. Because of the difficulty in consuming 4.4 grams of protein per kg body weight daily, every subject in the high protein group acquired their additional protein calories primarily from whey protein powder. It has been shown that the thermic effect is greater with whey versus casein or soy protein. Recently scientists demonstrated that consuming similar calories and protein during resistance training in initially untrained individuals resulted in greater gains in lean body mass in the whey supplemented group versus soy or carbohydrate. Thus, one might speculate that if the protein dose or intake is sufficiently high, it may not matter what that particular protein source may be.


This is the first investigation in resistance-trained individuals which demonstrates that a hypercaloric high protein diet does not contribute to a fat mass gain. Furthermore, there was no change in body weight or lean body mass. This might no seem so significant but there are so many advantages to a high-protein diet. If fat isn’t metabolized then this is a huge advantage to your metabolic rate, and then there’s the satiety perspective, the fullness that protein-rich diets provide. It would be intriguing to ascertain if a high protein diet concurrent with a heavy resistance bodybuilding training regimen would affect body composition (i.e. increase lean body mass and lower fat mass).

A vegetarian diet is completely fine as long as you add meat  =