Negative energy balance during military operations can be severe and result in significant reductions in fat-free mass (FFM). Consuming supplemental high-quality protein following such military operations may accelerate restoration of FFM. Body composition (dual-energy x-ray absorptiometry) and whole-body protein turnover (single-pool 15N-alanine method) were determined before (PRE) and after 7 d (POST) of severe negative energy balance during military training in 63 male US Marines (mean±SD, 25±3 y, 84±9 kg). After POST measures were collected, volunteers were randomized to receive higher-protein (HIGH: 1103 kcal/d, 133 g protein/d), moderate protein (MOD: 974 kcal/d, 84 g protein/d), or carbohydrate-based low protein control (CON: 1042 kcal/d, 7 g protein/d) supplements, in addition to a self-selected, ad libitum diet, for the 27 d intervention (REFED). Measurements were repeated POST-REFED. POST total body mass (TBM, -5.8±1.0 kg, -7.0%), FFM (-3.1±1.6 kg, -4.7%), and net protein balance (-1.7±1.1 g protein/kg/d) were lower and proteolysis (1.1±1.9 g protein/kg/d) was higher compared to PRE (P<0.05). Self-selected, ad libitum dietary intake during REFED was similar between groups (3507 ± 730 kcal/d, 2.0±0.5 g protein/kg/d). However, diets differed by protein intake due to supplementation (CON: 2.0±0.4, MOD: 3.2±0.7, HIGH: 3.5±0.7 g/kg/d; P<0.05) but not total energy (4498±725 kcal/d). All volunteers, independent of group assignment, achieved positive net protein balance (0.4±1.0 g protein/kg/d) and gained TBM (5.9±1.7 kg, 7.8%) and FFM (3.6±1.8 kg, 5.7%) POST-REFED compared to POST (P<0.05). Supplementing ad libitum, energy-adequate, higher-protein diets with additional protein may not be necessary to restore FFM after short-term severe negative energy balance.
- negative energy balance
- protein balance
- Copyright © 2016, Journal of Applied Physiology