Efficacy of HMB supplementation as an adjunct to resistance training in older adults: a comprehensive meta-analysis

BACKGROUND: Resistance training has robust evidence for improving muscle health in older adults; however, the additional benefit of adjunctive supplementation with β-hydroxy β-methylbutyrate (HMB) remains unclear. This systematic review and meta-analysis evaluated the effect of HMB supplementation combined with resistance training on body composition and muscle strength in adults aged 50 years and older. METHODS: Four databases (PubMed, Scopus, Clinicaltrials.gov, and Cochrane) were systematically searched for randomized controlled trials investigating HMB supplementation with resistance training in older adults. The main results examined fat mass, muscle mass, and muscle strength. Meta-analyses were conducted using robust variance estimation with small-sample corrections. The Cochrane RoB 2.0 tool was used to assess the risk of bias. RESULTS: A total of 561 participants were involved in 13 RCTs. According to meta-analysis data, supplementing with HMB is not advantageous concerning fat mass (SMD = 0.24, 95% CI: -0.01 to 0.49), muscle mass (SMD = 0.05, 95% CI: -0.10 to 0.20), and muscle strength (SMD = 0.04, 95% CI: -0.72 to 0.63). There was low heterogeneity for body composition outcomes but high heterogeneity for strength measures. No evidence of publication bias was detected. CONCLUSIONS: The combination of HMB supplementation and resistance training does not improve body composition or muscle strength in adults aged 50 years and older. Based on the available evidence, HMB supplementation cannot be recommended as a routine adjunct to resistance training in individuals who are able to undertake structured exercise.