Leucine supplementation during caloric restriction in adults at risk of metabolic syndrome: An 8 week double blind randomized controlled trial

Abstract

Abstract Background: Leucine (Leu) supplementation per se could benefit fat-free mass (FFM)/function and improve glucose metabolism. Objectives: To determine whether leucine supplementation during caloric restriction blunted the loss of FFM, increased the loss of fat mass (FM) and impacted glucose tolerance. Design: Thirty-seven adults, aged 20-65 y with increased waist circumference (>80 cm for females and >94 cm for males) and at least another component of metabolic syndrome (MetS) were studied in a parallel, double blind randomized control trial (RCT). Participants were allocated randomly to either an intervention (leucine – 3 g/d) or placebo (lactose - 2.67 g/d) group, while following an individualised calorie-restricted diet over an 8-week period. Body composition (DEXA), oral glucose tolerance test (OGTT), insulin and components of MetS were measured before and after the trial. Analysis of covariance assessed the effect of the leucine intervention on an intention-to-treat (ITT) principle. Bootstrapping method with 1000 bootstrap samples was used to derive parameter estimates, standard errors, p values, and 95% confidence intervals for all outcomes. Results: Adjusted for baseline values and other covariates, FFM (p=0.045) and lean tissue mass (LTM) (p=0.050) were significantly higher following Leu. These outcomes were modified by a significant treatment x gender interaction that indicated Leu had the greater effect in men. Adjusted for body composition changes, there were no differences in insulin sensitivity, oral glucose tolerance, or MetS components. Conclusion: Short-term leucine supplementation resulted in a greater preservation of FFM and LTM particularly in men.