title: Optimized dietary strategies to protect skeletal muscle mass during periods of unavoidable energy deficit.
abstract: Interactions between dietary protein and energy balance on the regulation of human skeletal muscle protein turnover are not well described. A dietary protein intake above the recommended dietary allowance during energy balance typically enhances nitrogen retention and up-regulates muscle protein synthesis, which in turn may promote positive protein balance and skeletal muscle accretion. Recent studies show that during energy deficit, muscle protein synthesis is down-regulated with concomitant increases in ubiquitin proteasome-mediated muscle proteolysis and nitrogen excretion, reflecting the loss of skeletal muscle mass. However, consuming high-protein diets (1.6-2.4 g/kg per day), or high-quality, protein-based meals (15-30 g whey) during energy deficit attenuates intracellular proteolysis, restores muscle protein synthesis, and mitigates skeletal muscle loss. These findings are particularly important for physically active, normal-weight individuals because attenuating the extent to which skeletal muscle mass is lost during energy deficit could prevent decrements in performance, reduce injury risk, and facilitate recovery. This article reviews the relationship between energy status, protein intake, and muscle protein turnover, and explores future research directives designed to protect skeletal muscle mass in physically active, normal-weight adults.
authors.affiliation: Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts, USA stefan.pasiakos@usarmy.mil.
authors.forename: Stefan M
authors.initials: SM
authors.lastname: Pasiakos
authors.affiliation: Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts, USA.
authors.forename: Lee M
authors.initials: LM
authors.lastname: Margolis
authors.affiliation: Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts, USA.
authors.forename: Jeb S
authors.initials: JS
authors.lastname: Orr
mesh_terms: D000328:Adult; D004032:Diet; D004044:Dietary Proteins / Q000008:administration & dosage*; D002149:Energy Intake; D006801:Humans; D044342:Malnutrition / Q000378:metabolism / Q000473:pathology; D008889:Military Personnel; D009124:Muscle Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000378:metabolism*; D009751:Nutritional Requirements; D059748:Proteolysis
chemical_list: D004044:Dietary Proteins; D009124:Muscle Proteins
keywords: lean body mass; leucine; mTORC1; military