title: Effects of high-protein diets on fat-free mass and muscle protein synthesis following weight loss: a randomized controlled trial.
abstract: The purpose of this work was to determine the effects of varying levels of dietary protein on body composition and muscle protein synthesis during energy deficit (ED). A randomized controlled trial of 39 adults assigned the subjects diets providing protein at 0.8 (recommended dietary allowance; RDA), 1.6 (2×-RDA), and 2.4 (3×-RDA) g kg(-1) d(-1) for 31 d. A 10-d weight-maintenance (WM) period was followed by a 21 d, 40% ED. Body composition and postabsorptive and postprandial muscle protein synthesis were assessed during WM (d 9-10) and ED (d 30-31). Volunteers lost (P<0.05) 3.2 ± 0.2 kg body weight during ED regardless of dietary protein. The proportion of weight loss due to reductions in fat-free mass was lower (P<0.05) and the loss of fat mass was higher (P<0.05) in those receiving 2×-RDA and 3×-RDA compared to RDA. The anabolic muscle response to a protein-rich meal during ED was not different (P>0.05) from WM for 2×-RDA and 3×-RDA, but was lower during ED than WM for those consuming RDA levels of protein (energy × protein interaction, P<0.05). To assess muscle protein metabolic responses to varied protein intakes during ED, RDA served as the study control. In summary, we determined that consuming dietary protein at levels exceeding the RDA may protect fat-free mass during short-term weight loss.
authors.affiliation: Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine, 15 Kansas St., Bldg 42, Natick, MA 01760, USA. stefan.pasiakos@us.army.mil
authors.forename: Stefan M
authors.initials: SM
authors.lastname: Pasiakos
authors.forename: Jay J
authors.initials: JJ
authors.lastname: Cao
authors.forename: Lee M
authors.initials: LM
authors.lastname: Margolis
authors.forename: Edward R
authors.initials: ER
authors.lastname: Sauter
authors.forename: Leah D
authors.initials: LD
authors.lastname: Whigham
authors.forename: James P
authors.initials: JP
authors.lastname: McClung
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Rood
authors.forename: John W
authors.initials: JW
authors.lastname: Carbone
authors.forename: Gerald F
authors.initials: GF
authors.lastname: Combs
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Young
mesh_terms: D000328:Adult; D000886:Anthropometry; D001823:Body Composition / Q000187:drug effects / Q000502:physiology*; D004044:Dietary Proteins / Q000494:pharmacology*; D002149:Energy Intake / Q000187:drug effects; D005260:Female; D006801:Humans; D008297:Male; D009124:Muscle Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism*; D019518:Postprandial Period; D015431:Weight Loss / Q000187:drug effects / Q000502:physiology*; D055815:Young Adult
chemical_list: D004044:Dietary Proteins; D009124:Muscle Proteins
keywords: energy deficit; fractional synthesis rate; nitrogen balance; postprandial; recommended dietary allowance; skeletal muscle