β-hydroxy-β-methylbutyrate (calcium: HMB-Ca and free acid: HMB-FA) and α-hydroxyisocaproic acid (α-HICA) are leucine metabolites that have been proposed to improve body composition and strength when combined with resistance exercise training (RET). In this double-blind randomized controlled pragmatic trial, we evaluated the effects of off-the-shelf supplements: α-HICA, HMB-FA and HMB-Ca, on RET-induced changes in body composition and performance. Forty men were blocked randomized to receive α-HICA (n = 10, fat-free mass [FFM] = 62.0 ± 7.1 kg), HMB-FA (n = 11, FFM = 62.7 ± 10.5 kg), HMB-Ca (n = 9, FFM = 65.6 ± 10.1 kg) or placebo (PLA; n = 10, FFM = 64.2 ± 5.7 kg). The training protocol consisted of a whole-body resistance training routine, thrice weekly for 8 weeks. Body composition was assessed by dual-energy x-ray absorptiometry (DXA) and total body water (TBW) by whole-body bioimpedance spectroscopy (BIS), both at baseline and at the end of weeks 4 and 8. Time-dependent changes were observed for increase in trunk FFM (p < 0.05). No statistically significant between-group or group-by-time interactions were observed. Supplementation with HMB (FA and Ca) or α-HICA failed to enhance body composition to a greater extent than placebo. We do not recommend these leucine metabolites for improving body composition changes with RET in young adult resistance trained men.
Keywords: Resistance training; fat-free mass; leucine metabolites.