The supplementation of l-carnitine does not promote alterations in the resting metabolic rate and in the use of energetic substrates in physically active individuals

Abstract

Purpose: To investigate the effects of L-carnitine supplementation, over thirty days, on the resting metabolic rate (RMR) and oxidation of free fatty acids (FFA) under rested or exercised conditions. Subjects and methods: Twenty-one overweight active volunteers (40 to 58 years old) were randomized into two groups: supplemented (GS; N = 11; 1,8 g/day of L-carnitine) or placebo (GP; N = 10; maltodextrin). Caloric intake, anthropometry, RMR, VO2max, respiratory exchange ratio and plasma FFA were measured. Results: No significant changes were found in the caloric intake (-244,66 vs. -126,00 kcal/day), body composition (-0.07 vs. -0.17 kg/m2), RMR (0.06 vs. -0.02 kcal/day), respiratory exchange ratio at rest (3.69 vs. -1.01) and exercise (0.01 vs. -0.01) or VO2max (0.50 vs. 1.25 mL/kg/min) between GS and GP. Plasma FFA levels were increased under resting conditions only in the GP group (0.27), but no significant changes were observed before or after physical activity in any of the groups. Conclusion: Supplementation with L-carnitine caused no changes in the variables analyzed in this study.