Essential Amino Acids and Protein Kinetics During Caloric Deprivation

Overview

The amount of essential amino acids (EAA) necessary to maximally stimulate muscle protein synthesis and optimize whole-body net protein balance during caloric deprivation has not been determined. This study will address that gap in knowledge by examining the resting and post-exercise muscle and whole-body protein kinetic responses to ingesting varying amounts of EAA after a 5 day period of negative energy balance. This study will provide the initial evidence to support the development of a recovery-based food product for military combat rations.

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.