Across 7 high-quality RCTs enrolling 472 older adults with sarcopenia, combining strength training with whey protein or HMB supplementation produced significant gains in fat-free mass (Hedge's g = 0.39), maximal isometric handgrip strength (g = 1.38), chair stand performance (g = 0.33), and 6-minute walk distance (g = 0.33). Critically, whey protein paired with resistance training drove a meaningful handgrip effect (g = 0.49), while HMB combined with training failed to reach significance — a distinction the pooled analysis makes visible for the first time in a sarcopenia-specific cohort.
The remarkably large effect size for handgrip strength warrants scrutiny: with only 7 trials and 472 participants, confidence intervals are wide and heterogeneity risk remains real even with subgroup modelling. Sarcopenia research chronically suffers from short intervention windows (typically 12–24 weeks) that may not capture long-term skeletal muscle remodeling. HMB's lukewarm performance here aligns with a growing body of evidence suggesting its benefits are more pronounced in untrained or malnourished individuals rather than those already engaged in structured resistance protocols. For clinicians and older adults, the practical signal is clear: leucine-rich whey protein remains the more evidence-supported adjunct to resistance training for preserving lean mass and functional mobility. This meta-analysis is confirmatory for whey protein but genuinely clarifying for HMB — shifting the question from 'does it work' to 'for whom, precisely.'