HMB is commonly marketed as a muscle-building supplement, but studies in people who already resistance train have generally found little additional benefit.
Other research has looked at a different use: whether HMB can help preserve muscle when inactivity, aging, or clinical recovery makes muscle loss more likely.
Key Takeaways
- HMB has not consistently increased muscle mass or strength in younger adults undergoing resistance training.
- A 2026 meta-analysis found no additional muscle or strength benefit when older adults combined HMB with resistance training.
- In a small randomized trial, older adults taking HMB lost substantially less lean mass during 10 days of complete bed rest.
- Across mixed populations, an umbrella review found small average improvements in muscle mass, fat-free mass, and strength.
What Is HMB?
Beta-hydroxy-beta-methylbutyrate, or HMB, is produced during the metabolism of leucine, an essential branched-chain amino acid.
Supplemental HMB has been studied for its effects on skeletal muscle, including muscle mass, strength, and the preservation of lean tissue during periods of reduced activity.
Does HMB Help Build Muscle in Younger Adults?
A 2020 systematic review and meta-analysis examined HMB supplementation in adults aged 18 to 45 who were participating in resistance training.
Eleven studies were included in the analyses. Body-composition data involved 302 participants, while 248 participants were included in the strength analysis.
HMB did not significantly improve fat-free mass, fat mass, bench-press strength, lower-body strength, or overall strength. A small increase in total body mass was reported, but it was not accompanied by an increase in fat-free mass (Jakubowski et al., 2020).
Does HMB Add Anything for Older Adults Who Resistance Train?
A 2026 meta-analysis examined whether HMB provides additional benefits when older adults are already participating in resistance training.
The review included 13 randomized controlled trials involving 561 adults aged 50 or older.
HMB did not significantly improve muscle mass, muscle strength, or fat mass compared with resistance training without HMB. The estimated effect on muscle mass was 0.05 standard deviations (95% CI, -0.10 to 0.20), while the estimate for muscle strength was 0.04 (95% CI, -0.72 to 0.63) (Wang et al., 2026).
Can HMB Reduce Muscle Loss During Inactivity?
Deutz and colleagues studied healthy adults aged 60 to 76 who underwent 10 days of complete bed rest. Participants received either placebo or 3 grams of calcium HMB per day, beginning five days before bed rest.
Nineteen participants were evaluable after the bed-rest period.
The control group lost an average of 2.05 kg of total lean body mass. After exclusion of one prespecified outlying DXA result, the HMB group lost 0.17 kg, a statistically significant between-group difference (Deutz et al., 2013).
HMB did not produce a corresponding significant improvement in the study’s measures of physical function.
The trial was small, and several authors were affiliated with Abbott Nutrition, which funded the research.
What Do Meta-Analyses Show Overall?
A 2025 umbrella review combined 11 previous meta-analyses comprising 41 datasets and participants ranging in age from 23 to 79 years.
Across these populations, HMB was associated with small improvements in muscle mass (effect size 0.21), fat-free mass (0.22), and muscle strength (0.27). There was no significant effect on overall body mass or fat mass (Bideshki et al., 2025).
The underlying reviews varied substantially in methodological quality: five were rated high quality using AMSTAR 2, three low quality, and three critically low quality.
The pooled studies also included people with different ages, activity levels, and risks of muscle loss, so the average effect cannot be assumed to apply equally to each group.
Has HMB Been Studied During Surgical Recovery?
A 2025 systematic review and meta-analysis examined HMB-containing interventions in 11 randomized trials involving 575 surgical patients.
The interventions were associated with an average reduction in hospital stay of approximately 0.9 days and a lower postoperative complication rate, with a pooled relative risk of 0.50. Some measures, including mid-arm muscle circumference, appendicular skeletal muscle mass, and six-minute walking distance, also favored the intervention. Overall skeletal muscle mass and lean body mass did not significantly improve (Hu et al., 2025).
Some trials used nutritional formulations containing HMB alongside other ingredients, making it difficult to isolate HMB’s contribution. Study protocols, patient populations, and methods of assessing muscle also varied.
Bottom Line
HMB appears to have limited value as an add-on for people already receiving a strong muscle-building stimulus from resistance training.
Its more plausible role is in situations where preserving existing muscle is difficult, such as prolonged inactivity or some clinical settings. The evidence for those uses is less extensive, but it makes HMB more interesting as a potential muscle-preservation supplement than as a way to increase the gains already produced by resistance training.
References
Bideshki, M. V., Behzadi, M., Jamali, M., Jamilian, P., Zarezadeh, M., & Pourghassem Gargari, B. (2025). Ergogenic benefits of β-hydroxy-β-methyl butyrate (HMB) supplementation on body composition and muscle strength: An umbrella review of meta-analyses. Journal of Cachexia, Sarcopenia and Muscle, 16(1), e13671. https://doi.org/10.1002/jcsm.13671
Deutz, N. E. P., Pereira, S. L., Hays, N. P., Oliver, J. S., Edens, N. K., Evans, C. M., & Wolfe, R. R. (2013). Effect of β-hydroxy-β-methylbutyrate (HMB) on lean body mass during 10 days of bed rest in older adults. Clinical Nutrition, 32(5), 704–712. https://doi.org/10.1016/j.clnu.2013.02.011
Hu, Y.-G., Shi, J.-H., Yu, D.-X., & Huang, H.-B. (2025). The effects of beta-hydroxy-beta-methyl butyrate supplementation in surgical patients: A systematic review and meta-analysis of randomized controlled trials. Frontiers in Nutrition, 12, 1621206. https://doi.org/10.3389/fnut.2025.1621206
Jakubowski, J. S., Nunes, E. A., Teixeira, F. J., Vescio, V., Morton, R. W., Banfield, L., & Phillips, S. M. (2020). 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. Nutrients, 12(5), 1523. https://doi.org/10.3390/nu12051523
Wang, G., Jawed, I., Tufail, M., Sharaf, M. S., Bin Gulzar, A. H., Ul Ain, H. Q., Umair, M., Kumar, D., & Jabeen, S. (2026). Efficacy of HMB supplementation as an adjunct to resistance training in older adults: A comprehensive meta-analysis. Age and Ageing, 55(3), afag073. https://doi.org/10.1093/ageing/afag073
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