The role of HMB supplementation in enhancing the effects of resistance training in older adults: a systematic review and meta-analysis on muscle quality, body composition, and physical function

Abstract

Background/objectives: Resistance training (RT) is a key strategy to counteract age-related declines in muscle strength and physical function. β-hydroxy-β-methylbutyrate (HMB) has been proposed as a complementary supplement to enhance these adaptations. However, the additional effects of RT plus HMB (RT+HMB) compared with RT alone remain unclear. This systematic review and meta-analysis evaluated the effects of RT+HMB versus RT alone on body composition, muscle quality (MQ), and physical function in older adults.

Methods: Following PRISMA guidelines (PROSPERO: CRD420251144810), six databases (PubMed, Scopus, Cochrane Library, CINAHL, Web of Science, and ScienceDirect) were searched up to July 2025. Randomized controlled trials comparing RT+HMB with RT alone were included. Methodological quality was assessed with the PEDro scale and risk of bias using Cochrane RoB 2. Pooled standardized mean differences (SMDs) with 95% confidence intervals (CIs) were calculated.

Results: Ten trials (n = 596) met inclusion criteria. RT+HMB produced modest and borderline significant improvements in handgrip strength (SMD 0.24; 95% CI 0.00-0.48; p = 0.05) and moderate benefits in Short Physical Performance Battery (SPPB) scores (SMD 0.54; 95% CI 0.12-0.95; p = 0.01). No significant effects were observed for gait speed, appendicular lean mass, MQ, fat mass, or body weight (p > 0.05). Five trials (50%) were rated at high risk of bias, limiting confidence in pooled estimates.

Conclusions: HMB supplementation combined with RT may yield modest improvements in functional performance, particularly handgrip strength and overall physical function, without statically significant effects in body composition and MQ. Further high-quality RCTs are warranted to confirm its clinical relevance.