This randomized, parallel study will examine the effects of energy balance and varying magnitudes of energy deficit on 1) the protein kinetic responses to consuming high quality protein and 2) carbohydrate oxidation during steady-state exercise. Healthy adults, representative of active duty military personnel, will complete a 2 d energy balance phase followed by a randomly assigned, 5 d energy deficit phase (n=15 per group; 20%, 40% and 60% energy deficit). At the end of each energy phase the effects of energy balance and energy deficit severity on resting postabsorptive (fasting) and postprandial (after consuming \~34 g protein) muscle protein synthesis (MPS) and whole-body protein synthesis, breakdown, and balance (synthesis - breakdown) will be determined. On the next day, the effects energy balance and energy deficit severity on carbohydrate oxidation during steady-state exercise will be determined. Primary study procedures include anthropometric and body composition measures, resting metabolic rate measures, aerobic exercise, tightly controlled diet and exercise interventions, repeated blood sampling, stable isotope infusion, stable isotope ingestion, and percutaneous muscle biopsies. The following hypotheses will be tested: 1) Δ (postprandial - postabsorptive) MPS and Δ whole-body protein balance at rest will progressively decrease as magnitude of energy deficit increases and 2) exogenous carbohydrate oxidation will be higher and endogenous carbohydrate oxidation will be lower during steady-state exercise as magnitude of energy deficit increases.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
NONE
Enrollment
30
A combination of individualized exercise performed on a cycle ergometer and individualized dietary prescriptions will be used to achieve energy balance or the assigned energy deficits throughout the controlled feeding and testing periods
US Army Research Institute of Environmental Medicine
Natick, Massachusetts, United States
Whole-body protein balance
Determined using L-\[1-13C\]-leucine stable isotope.
Time frame: 2 days
Muscle Protein Synthesis
Determined using L-\[ring-2H5\]-phenylalanine stable isotope.
Time frame: 2 days
Carbohydrate Oxidation during Steady-state Exercise
Determined using U-13C-glucose stable isotope.
Time frame: 2 days
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