Essential Amino Acids and Protein Kinetics During Caloric Deprivation

Short-term negative energy balance downregulates muscle protein synthesis and upregulates whole-body proteolysis and amino acid (AA) oxidation, thereby increasing nitrogen excretion and exacerbating whole-body and skeletal muscle protein loss. Consumption of quality proteins high in essential amino acid (EAA) content may attenuate protein loss during energy deficit by restoring whole-body and skeletal muscle anabolic potential to that observed in a eucaloric state. During energy balance, muscle protein synthesis appears to be maximally stimulated after consuming 15 g of EAA at rest and after conventional resistance-type exercise. In response to a short-term energy deficit that downregulated basal muscle protein synthesis by as much as 27%, consuming 15 g (~7.5 g EAA) and 30 g (~15 g EAA) of whey protein after a bout of resistance exercise restored muscle protein synthesis rates to resting, fasted rates observed in the eucaloric state in a dose dependent manner. The effect of EAA intakes above 15 g on resting and post-exercise muscle protein synthesis and the whole-body protein anabolic response during acute energy deficit has not been determined. This study will assess resting and post-resistance exercise whole-body and skeletal muscle protein synthesis responses to across a spectrum of EAA intakes following a well-controlled, short-term (5-d) energy deficit (30% energy deficit). Using a randomized, double-blind, cross-over design, 20 resistance trained (≥ 2 d/wk for the past 6 mo) adults will undergo two, non-consecutive 5-d energy deficit periods, separated by a 14-d washout period. Resting and post-resistance exercise (single leg exercise model) whole-body protein turnover and skeletal muscle protein synthesis responses to two different doses of EAA (standard, 0.10 g/kg vs high, 0.30 g/kg) will be determined the morning after completing the 5-d energy deficit. This design will test the hypothesis that higher absolute doses of EAA are required to maintain resting and post-exercise anabolic responses during energy deficit.

Inclusion criteria

• Men and women aged 18 - 35 years
• Body mass index < 30.0 kg/m2
• Healthy without evidence of chronic illness or musculoskeletal injury as determined by the USARIEM Office of Medical Support and Oversight (OMSO)
• Resistance exercise trained defined by self-report as performing ≥ 2 sessions/wk for previous 6 mo
• Refrain from taking any nonsteroidal anti-inflammatory drugs (e.g., aspirin, Advil®, Aleve®, Naprosyn®), or any other aspirin-containing product for 10 days before starting and at least 5 days after completing the study
• Willing to refrain from alcohol, smoking any nicotine product (includes e-cigarettes); vaping, chewing tobacco, caffeine, and dietary supplement use throughout the entire study period
• Supervisor approval for federal civilian employees and non-HRV active duty military personnel working within the US Army Natick Soldier Systems Center

Exclusion criteria

• Musculoskeletal injuries that compromise exercise capability as determined by the USARIEM Office of Medical Support and Oversight (OMSO)
• Metabolic or cardiovascular abnormalities, gastrointestinal disorders (e.g., kidney disease, diabetes, cardiovascular disease, etc.)
• Abnormal PT/PTT test or problems with blood clotting
• History of complications with lidocaine
• Present condition of alcoholism, anabolic steroids, or other substance abuse issues
• Blood donation within 8-wk of beginning the study
• Pregnancy (self-report or results of urine pregnancy test before body composition testing)
• Unwillingness or inability to consume study diets or foods provided