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Title: Effects of high protein diets on fat-free mass and muscle protein synthesis following weight loss: a randomized controlled trial

Author
item PASIAKOS, STEFAN - Us Army Medical Research Institute
item Cao, Jay
item MARGOLIS, LEE - Us Army Medical Research Institute
item SAUTER, EDWARD - University Of North Dakota
item Whigham Grendell, Leah
item MCCLUNG, JAMES - Us Army Medical Research Institute
item ROOD, JENNIFER - Louisana State University
item CARBONE, JOHN - Eastern Michigan University
item Combs, Gerald
item YOUNG, ANDREW - Us Army Medical Research Institute

Submitted to: Journal of Federation of American Societies for Experimental Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2013
Publication Date: 6/5/2013
Citation: Pasiakos, S.M., Cao, J.J., Margolis, L.M., Sauter, E.R., Whigham Grendell, L.D., Mcclung, J.P., Rood, J.C., Carbone, J.W., Combs, G.F., Young, A.J. 2013. Effects of high protein diets on fat-free mass and muscle protein synthesis following weight loss: a randomized controlled trial. Journal of Federation of American Societies for Experimental Biology. doi: 10.1096/fj.13-230227.

Interpretive Summary: High protein diets may be beneficial to preserve lean body mass and sustain skeletal muscle protein metabolism during short-term weight loss in normal-weight adults. To determine the effects of varying levels of dietary protein intake on body composition and muscle protein synthesis (MPS) during energy deficit (ED), a randomized controlled trial of 39 recreationally active adults (19-42 years, body mass index 22-29 kg/m2) was conducted. Volunteers were assigned diets providing protein at 0.8 (recommended dietary allowance; RDA), 1.6 (2X-RDA), and 2.4 (3X-RDA) g·kg-1·d-1 for 31 days. A 10-day weight maintenance (WM) period was followed by 21 days of ED, during which energy intake was restricted to 60% of daily requirements. Overall, volunteers lost 3.2 ± 0.2 kg body weight during ED regardless of dietary protein. However, the proportion of weight loss attributed to reductions in fat-free mass was lower and the loss of fat mass was higher for 2X-RDA and 3X-RDA compared to RDA. The anabolic skeletal muscle response to a protein rich meal ('PP-PA MPS) during ED was not different from WM for 2X-RDA and 3X-RDA, but was lower during ED than WM for those consuming RDA levels of protein. We conclude that normal-weight adults may gain a metabolic advantage that protects muscle mass during short-term weight loss by consuming dietary protein above the RDA. Consuming high protein diets during weight loss may spare lean body mass and sustain skeletal muscle anabolic responses to dietary protein.

Technical Abstract: Context: The benefits of high protein diets for sparing lean body mass and sustaining skeletal muscle protein metabolism during short-term weight loss in normal-weight adults are not well described. Objective: Determine the effects of varying levels of dietary protein intake on body composition and muscle protein synthesis (MPS) during energy deficit (ED). Design, Setting, and Participants: A randomized controlled trial of 39 recreationally active adults (19-42 years, body mass index 22-29 kg/m2) admitted to a residential metabolic ward between October 2010 and November 2011. Intervention: Volunteers were assigned diets providing protein at 0.8 (recommended dietary allowance; RDA), 1.6 (2X-RDA), and 2.4 (3X-RDA) g·kg-1·d-1 for 31 days. A 10-day weight maintenance (WM) period was followed by 21 days of ED, during which energy intake was restricted to 60% of daily requirements. Main Outcome Measures: Body composition was measured by dual-energy x-ray absorptiometry during WM (day 9) and ED (day 30). Postabsorptive (PA) and postprandial (PP, mixed meal with 20 g protein) MPS were determined at rest during WM (day 10) and ED (day 31) using muscle biopsies and primed, constant L-[2H5]-phenylalanine infusions. Results: Overall, volunteers lost (P < 0.05) 3.2 ± 0.2 kg body weight during ED regardless of dietary protein. However, the proportion of weight loss attributed to reductions in fat-free mass was lower (P < 0.05) and the loss of fat mass was higher (P < 0.05) for 2X-RDA and 3X-RDA compared to RDA. The anabolic skeletal muscle response to a protein rich meal ('PP-PA MPS) during ED was not different (P > 0.05) from WM for 2X-RDA and 3X-RDA, but was lower during ED than WM for those consuming RDA levels of protein (energy-by-protein interaction, P< 0.05). Conclusions: These findings suggest that normal-weight adults may gain a metabolic advantage that protects muscle mass during short-term weight loss by consuming dietary protein above the RDA. Consuming high protein diets during weight loss may spare lean body mass and sustain skeletal muscle anabolic responses to dietary protein.