Bodybuilders who already consume sufficient protein, and who boost their daily protein intake to 3-4 g per kg bodyweight, will not become more muscled or stronger. They will lose fat mass though, according to a human study published by the American sports scientist Jose Antonio in the Journal of the International Society of Sports Nutrition.
How much protein?
According to current knowledge, the muscles of strength athletes grow optimally at a daily intake of 1.5-2 g protein per kg bodyweight. But what happens if strength athletes consume higher amounts of protein? Do they get fat? Or sick?
Researchers at Nova Southeastern University in Florida set out to answer this question in a human study. They performed an 8-week experiment on 48 young, recreational bodybuilders, all of whom had been training regularly for a few years and consumed about 2 g protein per kg bodyweight each day.
The researchers asked half of the subjects to continue with the same protein intake [NP], and they asked the other group to drastically increase their protein intake but with as few other changes as possible in their diet [HP]. The researchers left it to the subjects themselves to decide whether to increase their protein intake by using protein supplements or making dietary changes.
All subjects used the same training schedule.
The protein intake in both groups increased during the experiment. As the table below shows, the protein intake in the NP group increased to 2.3 g protein per kg bodyweight per day. In the HP group the intake increased to 3.4 g protein per day. The increase in protein intake also meant an increase in kilocalorie consumption.
The subjects who consumed the highest amount of proteins built up the same amount of lean body mass as the subjects who ‘only’ consumed 2.3 g protein per kg bodyweight daily. So an extremely high protein intake did not result in even more muscle growth.
The extreme protein intake did however lead to a bigger decrease in fat mass. That’s interesting, because the bodybuilders in this group did consume about 400 kilocalories more than the other group. It would seem that the extremely high protein intake boosted the resting energy expenditure.
The bodybuilders in both groups gained strength. The progression was slightly bigger in the group that consumed a daily 2.3 g protein per kg bodyweight, but the differences between the groups were not statistically significant.
The researchers examined the subjects’ blood, looking for signs of damage, for example to the kidneys, but found no indications of harmful effects as a result of the high protein intake.
“This study as well as previous work from our lab [J Int Soc Sports Nutr. 2014 May 12;11:19.] suggests that gains in body fat are unlikely to occur with protein overfeeding”, the researchers concluded. “This investigation confutes the notion that trained subjects need only 1.5–2.0 grams of protein per kg body weight daily and that intakes above that are superfluous.”
A high protein diet (3.4 g/kg/d) combined with a heavy resistance training program improves body composition in healthy trained men and women – a follow-up investigation
The consumption of a high protein diet (>4 g/kg/d) in trained men and women who did not alter their exercise program has been previously shown to have no significant effect on body composition. Thus, the purpose of this investigation was to determine if a high protein diet in conjunction with a periodized heavy resistance training program would affect indices of body composition, performance and health.
Forty-eight healthy resistance-trained men and women completed this study (mean?±?SD; Normal Protein group [NP n?=?17, four female and 13 male]: 24.8?±?6.9 yr; 174.0?±?9.5 cm height; 74.7?±?9.6 kg body weight; 2.4?±?1.7 yr of training; High Protein group [HP n?=?31, seven female and 24 male]: 22.9?±?3.1 yr; 172.3?±?7.7 cm; 74.3?±?12.4 kg; 4.9?±?4.1 yr of training). Moreover, all subjects participated in a split-routine, periodized heavy resistance-training program. Training and daily diet logs were kept by each subject. Subjects in the NP and HP groups were instructed to consume their baseline (~2 g/kg/d) and >3 g/kg/d of dietary protein, respectively.
Subjects in the NP and HP groups consumed 2.3 and 3.4 g/kg/day of dietary protein during the treatment period. The NP group consumed significantly (p?< ?0.05) more protein during the treatment period compared to their baseline intake. The HP group consumed more (p?0.05) total energy and protein during the treatment period compared to their baseline intake. Furthermore, the HP group consumed significantly more (p?0.05) total calories and protein compared to the NP group. There were significant time by group (p???0.05) changes in body weight (change: +1.3?±?1.3 kg NP, ?0.1?±?2.5 HP), fat mass (change: ?0.3?±?2.2 kg NP, ?1.7?±?2.3 HP), and % body fat (change: ?0.7?±?2.8 NP, ?2.4?±?2.9 HP). The NP group gained significantly more body weight than the HP group; however, the HP group experienced a greater decrease in fat mass and % body fat. There was a significant time effect for FFM; however, there was a non-significant time by group effect for FFM (change: +1.5?±?1.8 NP, +1.5?±?2.2 HP). Furthermore, a significant time effect (p???0.05) was seen in both groups vis a vis improvements in maximal strength (i.e., 1-RM squat and bench) vertical jump and pull-ups; however, there were no significant time by group effects (p???0.05) for all exercise performance measures. Additionally, there were no changes in any of the blood parameters (i.e., basic metabolic panel). Conclusion Consuming a high protein diet (3.4 g/kg/d) in conjunction with a heavy resistance-training program may confer benefits with regards to body composition. Furthermore, there is no evidence that consuming a high protein diet has any deleterious effects. Source: http://www.jissn.com/content/12/1/39