The consumption of dietary protein is important for resistance-trained individuals. It has been posited that intakes of 1.4 to 2.0 g/kg/day are needed for physically active individuals. Thus, the purpose of this investigation was to determine the effects of a very high protein diet (4.4 g/kg/d) on body composition in resistance-trained men and women.
Thirty healthy resistance-trained individuals participated in this study (mean ± SD; age: 24.1 ± 5.6 yr; height: 171.4 ± 8.8 cm; weight: 73.3 ± 11.5 kg). Subjects were randomly assigned to one of the following groups: Control (CON) or high protein (HP). The CON group was instructed to maintain the same training and dietary habits over the course of the 8 week study. The HP group was instructed to consume 4.4 grams of protein per kg body weight daily. They were also instructed to maintain the same training and dietary habits (e.g. maintain the same fat and carbohydrate intake). Body composition (Bod Pod®), training volume (i.e. volume load), and food intake were determined at baseline and over the 8 week treatment period.
The HP group consumed significantly more protein and calories pre vs post (p < 0.05). Furthermore, the HP group consumed significantly more protein and calories than the CON (p < 0.05). The HP group consumed on average 307 ± 69 grams of protein compared to 138 ± 42 in the CON. When expressed per unit body weight, the HP group consumed 4.4 ± 0.8 g/kg/d of protein versus 1.8 ± 0.4 g/kg/d in the CON. There were no changes in training volume for either group. Moreover, there were no significant changes over time or between groups for body weight, fat mass, fat free mass, or percent body fat.
Consuming 5.5 times the recommended daily allowance of protein has no effect on body composition in resistance-trained individuals who otherwise maintain the same training regimen. This is the first interventional study to demonstrate that consuming a hypercaloric high protein diet does not result in an increase in body fat.
Alex’s notes: Protein is a highly researched macronutrient with regards to exercise and athletes. An excellent, be it somewhat old, review by Tipton and Wolfe concluded that daily intakes of 2.5-3.0 g/kg (1.1-1.4 g/lb) of protein was not harmful for strength training athletes and may give small but important benefits. Any excess would simply be oxidized and the largest concern with a high protein intake is inadequate intake of other nutrients. However, It is not clear if protein overfeeding will result in body fat gains, despite it being blatantly obvious that overfeeding in general promotes weight gain.
The study at hand had 30 healthy, resistance-trained individuals (9 years average of training experience) divided into two groups. Both maintained their training routine and had a baseline protein intake of about 2 g/kg daily. The high-protein group consumed protein powder to increase protein to 4.4 g/kg bodyweight per day – an extra 145 grams of protein daily over baseline. Importantly, fat and carbohydrates were held constant so that the high-protein group ended up eating a surplus of about 800 calories per day from the increased protein.
Now, before we get to the VERY interesting results, we must acknowledge that food diaries are not the most reliable method of record keeping. Also, there was huge individual variance in the response to the protein overfeeding, as Jose Antonio (the author) stated on Facebook, plotting everyone individually makes it look like a shotgun hit the graph.
As for the results, there was NO CHANGE in lean body mass or fat mass or weight. It was like nothing happened (on average, remember that the variance was incredible between individuals). This occurred in spite of the fact that they consumed over 800 calories more per day for eight weeks. Certainly, this dispels the notion that a calorie is just a calorie.
One might suggest that the high thermic effect of protein may make it difficult to gain body weight during times of overfeeding. Protein uses about 20-25% of its energy to be metabolized, but this clearly could not account for the lack of weight gain. The subjects in the current study were resistance-trained subjects who were instructed to not alter their training regimen. Thus, the lack of body composition changes in our group may be attributable to the fact that it is very difficult for trained subjects to gain lean body mass and body weight in general without significant changes in their training program.
Overall, this is a weird study and more research is definitely needed. No blood work or standardized resistance training was done, and Jose Antonio currently has another study with the above in the works. I personally look forward to seeing how this plays out. For now, I suppose the only way to know how you respond is to double your protein intake while holding all else constant and see what happens. N=1.