Anabolism; And hypogonadism; BIA, bioelectrical impedance analysis; D2O, deuterium; DSMB, data and safety monitoring board; DXA, dual-energy x-ray absorptiometry; ECW, extracellular water; EDef, energy deficit; EIEE, exercise-induced energy expenditure; Energy deficit; Exercise; FBR, fractional breakdown rate; FFM, fat-free mass; FSR, fractional synthetic rate; HR, heart rate; HRR, heart rate reserve; ICW, intracellular water; ID, identification; IRB, Institutional Review Board; MRE, Meal; Optimizing Performance for Soldiers Trial I, OPS II; Optimizing Performance for Soldiers Trial II, PAR-Q+; Pennington Biomedical Research Center, PLA; Physical Activity Readiness Questionnaire+, PB; Ready-to-Eat, OPS I; Skeletal muscle; Sleep deprivation; TBW, total body water; TDEE, total daily energy expenditure; TDEI, total daily energy intake; TEST, testosterone experimental group; VO2max, maximal cardiorespiratory fitness; VO2peak, peak oxygen uptake; WBGT, wet bulb globe temperature; placebo experimental group, PS; protein breakdown, PBRC; protein synthesis, Q; ratings of perceived exertion, SUSOPS; repetition maximum, RNA; respiratory exchange ratio, RM; ribonucleic acid, RPE; sustained, multi-stressor military operations; whole-body nitrogen flux, RER