Stefan M. Pasiakos, Claire E. Berryman, J. Philip Karl, Harris R. Lieberman, Jeb S. Orr, Lee M. Margolis, John A. Caldwell, Andrew J. Young, Monty A. Montano, William J. Evans, Oshin Vartanian, Owen T. Carmichael, Kishore M. Gadde, Neil M. Johannsen, Robbie A. Beyl, Melissa N. Harris, and Jennifer C. Rood
Background: Severe energy deficits during military operations, produced by significant increases in exercise and limited dietary intake, result in conditions that degrade lean body mass and lower-body muscle function, which may be mediated by concomitant reductions in circulating testosterone. Methods: We conducted a three-phase, proof-of-concept, single centre, randomised, double-blind, placebo-controlled trial (CinicalTrials.gov, NCT02734238) of non-obese men: 14-d run-in, free-living, eucaloric diet phase; 28-d live-in, 55% exercise- and diet-induced energy deficit phase with (200 mg testosterone enanthate per week, Testosterone, n = 24) or without (Placebo, n = 26) exogenous testosterone; and 14-d recovery, free-living, ad libitum diet phase. Body composition was the primary end point; secondary endpoints included lower-body muscle function and health-related biomarkers. Findings: Following energy deficit, lean body mass increased in Testosterone and remained stable in Placebo, such that lean body mass significantly differed between groups [mean difference between groups (95% CI), 2.5 kg (3.3, 1.6); P