No effect of increasing protein intake during military exercise with severe energy deficit on body composition and performance

Abstract

In this study, we compare the effects of isocaloric high- (HIGH: 2 g kg−1d−1, n = 19) and low-protein diet (LOW: 1 g kg−1d−1, n = 19) on changes in body composition, muscle strength, and endocrine variables in response to a 10-day military field exercise with energy deficit, followed by 7 days of recovery. Body composition (DXA), one repetition maximum (1RM) bench and leg press, counter-movement jump height (CMJ) and blood variables were assessed before and after the exercise. Performance and blood variables were reassessed after 7days of recov-ery. The 10-day exercise resulted in severe energy deficit in both LOW and HIGH (−4373±1250, −4271±1075kcald−1) and led to decreased body mass (−6.1%, −5.2%), fat mass (−40.5%, −33.4%), 1RM bench press (−9.5%, −9.7%), 1RM leg press (−7.8%, −8.3%), and CMJ (−14.7%, −14.6%), with no differences between groups. No change was seen for fat-free mass. In both groups, the exercise led to a switch toward a catabolic physiological milieu, evident as reduced levels of anabolic hormones (testosterone, IGF-1) and increased levels of cortisol (more pronounced in HIGH, P<.05). Both groups also displayed substantial increases in creatine kinase. After 7days of recovery, most variables had returned to close-to pre-exercise levels, except for CMJ, which remained at reduced levels. In conclusion, increased protein intake during 10-day military field exercise with severe energy deficiency did not mitigate loss of body mass or impairment of physical performance