Efficacy of L-Leucine Supplementation Coupled with a Calorie-Restricted Diet to Promote Weight Loss in Mid-Life Women.

Objective: This study evaluated the effect of leucine supplementation coupled with a calorie-restricted diet over a 12-week period in mid-life overweight and obese women on body composition and resting metabolic rate (RMR).

Method: This study was a randomized, single-blind, placebo-controlled trial in which 34 women were randomly assigned to either 10 g leucine (LEU) or placebo daily, while following a calorie-restricted diet A dual energy x-ray absorptiometry (DXA) analysis, metabolic rate assessment via a BodyGem® and anthropometrics were performed at baseline and after the 12-week study to determine changes in fat mass, lean mass and RMR. Main variables were analyzed using 2 (condition) by 2 (time) mixed design ANOVAs with repeated measures. Odds ratio was calculated by counting the number of individuals gaining or maintaining lean mass ( ≤ .05).

Results: Both groups lost a significant amount of weight due to both fat and lean mass loss, but there was no significant difference between groups, with RMR remaining unchanged over the course of the study and not significantly different between groups. The loss in lean mass was noticeably less, though not statistically significant ( = 0.644) for the women in the LEU group, with 38% vs. 6%, gaining or retaining lean mass during the intervention relative to the placebo.

Conclusions: Our findings demonstrate that a greater proportion of mid-life overweight or obese women taking LEU supplements gained or maintained lean mass during intentional weight loss, though it did not reach a level of statistical significance.