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 recovery. 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.

Performance nutrition for cold-weather military operations

“…interleukin-6 and hepcidin) at the conclusion of the 4-day cold-weather training exercise [ 3 , 9 , 33 ]. Ineffectiveness of supplement protein foods to decrease the severity of energy deficit and subsequent physiological decrements has been corroborated by other laboratories assessing the impact of supplement protein intake during 8 and 10-day Norwegian cold-weather operations [ 34 , 35 ].…”

Testosterone status following short‐term, severe energy deficit is associated with fat‐free mass loss in U.S. Marines

“…Testosterone and body mass decrements have been observed during both moderate and severe energy deficits in healthy normal weight males, although the amount of fat‐free and fat mass loss varies widely (Alemany et al, 2008 ; Henning, Margolis, et al, 2014 ; Henning, Scofield, et al, 2014 ; Kyröläinen et al, 2008 ; Nindl, Alemany, et al, 2007 ; Nindl, Barnes, et al, 2007 ; Øfsteng et al, 2020 ; Pasiakos et al, 2013 ). In the current study, participants who maintained normal testosterone concentrations following a 7‐day severe energy deficit lost less whole‐body and trunk fat‐free mass and more whole‐body and trunk fat mass compared to those who experienced low testosterone concentrations following training.…”

“…In a previous study, healthy participants subjected to a 21‐day, 40% energy deficit, achieved with increased physical training and decreased food intake, lost 3.2 kg body mass, which coincided with a 16% decrease in total testosterone (Henning, Margolis, et al, 2014 ; Pasiakos et al, 2013 ). More extreme energy deficits (> 40%) lasting between 4–62 days, such as those that occur during US Special Operations Forces military training, result in substantial body weight, fat‐free mass, and fat mass loss that coincide with 27%–83% reductions in testosterone (Alemany et al, 2008 ; Henning, Scofield, et al, 2014 ; Kyröläinen et al, 2008 ; Nindl, Alemany, et al, 2007 ; Nindl, Barnes, et al, 2007 ; Øfsteng et al, 2020 ). However, the magnitude of testosterone decrements in response to energy deficit are quite variable, with some males maintaining normal testosterone concentrations and others falling below the normal range (< 10.5 nmol/L) (Alemany et al, 2008 ).…”

Feeding female soldiers: Consideration of sex-specific nutrition recommendations to optimise the health and performance of military personnel

“…High total daily energy expenditures (TDEE) and / or energy deficits are commonly reported during military training courses. [1][2][3][4][5][6] Energy deficit is associated with negative whole-body protein balance, 7,8 decreased lean body mass 3,9 and muscle performance, 3,[9][10][11][12][13] impaired endocrine function, 3,4,9,14 uncoupled bone turnover 15,16 and a loss of bone mass. 4,16 Appropriate nutritional strategies are important for military personnel to prevent maladaptive effects of high TDEE on health and performance, and to promote muscle, bone and physical performance adaptations to high volumes of exercise.…”

“…Given the anatomical, hormonal and physical performance sex differences, and sex differences in the physiological responses and musculoskeletal injury risk during military training, J o u r n a l P r e -p r o o f it is reasonable to question whether feeding strategies in the military should differ between men and women. The effects of nutritional interventions on physical performance, endocrine and musculoskeletal adaptations to military training are well studied, 4,7,9,11,14,28 but sex-specific requirements have not been considered. The aim of this review is to consider the evidence for sexspecific nutrition requirements to optimise the health and performance of military personnel.…”