Supplementation with the Leucine Metabolite β-hydroxy-β-methylbutyrate (HMB) does not Improve Resistance Exercise-Induced Changes in Body Composition or Strength in Young Subjects: A Systematic Review and Meta-Analysis.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of trials
PubMed 32456217 · doi:10.3390/nu12051523
What was done
Authors conducted a systematic review and meta-analysis searching Medline, Embase, CINAHL, and SportDiscus to assess the efficacy of β-hydroxy-β-methylbutyrate (HMB) supplementation in augmenting fat-free mass (FFM) and strength during resistance exercise training in adults aged 18–45 years. Investigated outcomes included total body mass (TBM), FFM, fat mass (FM), total 1RM, bench press 1RM, and lower-body 1RM. Fourteen studies met inclusion criteria, and 11 were included in the meta-analysis after data extraction and funnel plot exclusion (302 participants for body mass/composition, 248 for strength).
What was found
A significant effect was observed for total body mass gain. However, there were no significant effects on fat-free mass, fat mass, or any evaluated strength metric (total 1RM, bench press 1RM, or lower-body 1RM). Specific numerical effect sizes, point estimates, confidence intervals, and p-values were not provided in the abstract.
Why it matters
Despite frequent promotion of HMB for muscle hypertrophy and strength in athletic contexts, this meta-analysis indicates it does not meaningfully enhance body composition or strength adaptations to resistance training in young adults.
Limits
The abstract provides no numerical data, effect estimates, or confidence intervals. The total pooled sample size is relatively small (302 participants across 11 studies). Three of 14 eligible studies were excluded based on funnel plot analysis. Findings apply to young adults and do not address older populations experiencing sarcopenia or clinical muscle-wasting conditions.
Cited by
- supports HMB (beta-hydroxy beta-methylbutyrate) is a breakdown metabolite of leucine that has been shown in studies to improve muscle strength when taken as a supplement.