Whole-Body Protein Balance during Arctic Military Training Is Unaffected by Dietary Essential Amino Acid or Energy Density

BACKGROUND: Energy deficit severity and dietary protein intake are primary determinants of negative whole-body protein balance during strenuous military training. OBJECTIVES: This work aimed to determine whether attenuating energy deficits by providing low-volume energy-dense foods that may promote energy intake or consuming essential amino acid (EAA)-dense foods to facilitate an anabolic state preserves whole-body protein balance during strenuous cold-weather military training. METHODS: N-alanine. RESULTS: Energy expenditure (5341 ± 674 kcal/d), energy intake (4045 ± 738 kcal/d), and energy deficits (-1257 ± 599 kcal/d; 24 ± 11%) were not different (P > 0.05) between groups. Protein intake was >1.6 g/kg/d in all treatments. PRE to POST increases (P < 0.05) in protein flux (1.21 ± 0.23 vs. 1.34 ± 0.36 g N/kg/d), PS (3.46 ± 2.06 vs. 5.43 ± 2.86 g/kg/d), PB (6.26 ± 1.35 vs. 6.95 ± 2.12 g/kg/d), and NB (-2.80 ± 1.61 vs. -1.51 ± 1.60 g/kg/d) occurred independent of treatment. CONCLUSIONS: Soldiers achieved high protein intakes and modest energy deficits when provided 3 standard rations and 4 supplemental bars daily during cold-weather training. Supplemental bar energy or EAA density did not affect whole-body protein balance under these conditions, suggesting protein utilization remains independent of the macronutrient formulation of supplemental bars during military training scenarios with high protein intakes and moderate energy deficits. This trial was registered at clinicaltrials.gov as NCT05210205.