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Research · Supplements

HMB

In trained athletes and young lifters, meta-analyses found no change in strength or fat-free mass with HMB. In older adults and clinical patients, HMB added small gains in muscle mass and strength, but not on top of resistance training. Fat mass did not change in pooled trials. Muscle damage markers fell. Pooled early trials detected no adverse effects.

Add to Bio HackChecked 2026-11-13
Status
Dietary supplement in the US.
Also called
beta-hydroxy-beta-methylbutyrate, β-hydroxy-β-methylbutyrate, HMB-Ca, calcium HMB, HMB free acid, HMB-FA, myHMB, leucine metabolite
Taken for
muscle gain, strength, recovery, less muscle damage, preserving muscle with age or illness, fat loss

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help1

Reported risks2

What people take it for, and what was found

Shown to help1

Moderate

Muscle damage markers

Shown to lower the muscle damage markers creatine kinase and LDH after damaging exercise in healthy adults, mainly in studies over 6 weeks.

The numbers and sources
Effect
Across 10 studies (324 participants), HMB lowered creatine kinase by 60.71 U/L (95% CI -78.12 to -43.29) and, across 8 studies, LDH by 15.42 U/L (95% CI -22.2 to -8.6). The effect was significant in studies longer than 6 weeks [11].
Population
Healthy adults after damaging exercise [11].
Sources
[11]
Caveats
Blood markers, not soreness or performance.

Mixed results1

Moderate

Muscle mass and strength in older adults and patients

Mixed results: HMB raised muscle mass and strength slightly in older adults and patients, but not when added to resistance training.

The numbers and sources
Effect
In 9 RCTs (448 older adults), HMB raised fat-free mass (ES 0.37, 95% CI 0.16 to 0.58), with no change in fat mass. HMB alone raised fat-free mass (ES 0.59); HMB added to exercise did not (ES 0.06, 95% CI -0.26 to 0.38) [5]. In 21 RCTs (1,935 people over 50), HMB raised appendicular muscle mass by 1.56 kg (95% CI 0.03 to 3.09), lean mass by 0.28 kg, handgrip strength by 0.54 kg and gait speed by 0.06 m/s [6]. In 5 RCTs in sarcopenia, muscle mass index (SMD 0.32, 95% CI 0.00 to 0.64) and handgrip strength (SMD 0.65) rose, and gait speed did not change [7]. In 15 RCTs (2,137 patients with muscle-wasting conditions), HMB or HMB-containing supplements raised muscle mass (SMD 0.25, 95% CI -0.00 to 0.50) and strength (SMD 0.31, 95% CI 0.12 to 0.50) [8].
Population
Older adults [5][6]; people with sarcopenia [7]; hospital and clinical patients [8].
Sources
[5], [6], [7], [8], [9], [10]
Caveats
Many trials gave HMB in multi-ingredient nutrition drinks, so the effect of HMB alone is unclear [8]. No trial in [8] had low risk of bias in every category. Review [6] searched Chinese databases. Added to resistance training, HMB did not change muscle mass (SMD 0.05, 95% CI -0.10 to 0.20, 13 RCTs, 561 adults over 50) or strength [9], and a second review of 10 trials (596 older adults) found no change in lean mass, a borderline handgrip gain (SMD 0.24, 95% CI 0.00 to 0.48) and better physical performance scores (SMD 0.54), with half the trials at high risk of bias [10].

Not shown to help2

Strong

Strength and fat-free mass in trained athletes and young lifters

Not shown to change strength, fat-free mass or fat mass in trained athletes or young adults in resistance training.

The numbers and sources
Effect
In 6 RCTs of trained and competitive athletes (193 participants), effect sizes were trivial and not significant for bench press (0.00), leg press (0.09), fat-free mass (0.16) and fat mass (-0.20) [1]. In 11 studies of adults aged 18 to 45 in resistance training, HMB raised total body mass slightly but did not change fat-free mass, fat mass or strength [2]. In 5 studies of athletes, fat-free mass trended up (0.30, 95% CI -0.07 to 0.68, p = 0.08), apparently only when protein intake was under 1.6 g per kg a day [3].
Population
Trained and competitive athletes [1][3]; young adults in training [2].
Sources
[1], [2], [3]
Caveats
Small pooled samples. The ISSN position stand [4] reports body composition improvements across ages and training levels, but several of its authors disclose employment, consulting or patents tied to HMB.
Moderate

Fat loss

Not shown to lower fat mass in athletes, young lifters or older adults. One dieting trial that also gave protein found more fat loss.

The numbers and sources
Effect
Fat mass did not change significantly in pooled trials of athletes (ES -0.20) [1], young lifters [2] or older adults [5]. An umbrella review of 11 meta-analyses found no significant change in fat mass (ES 0.03) or body mass, alongside small gains in muscle mass (ES 0.21) and strength (ES 0.27) [12]. In one 12-week trial during calorie restriction, a powder with 3.0 g HMB and 24 g protein a day lowered body fat by 4.9 kg more than a maltodextrin control (95% CI -6.8 to -3.1) and kept skeletal muscle mass 1.3 kg higher [13].
Population
Athletes, young lifters and older adults [1][2][5][12]. 102 Chinese adults with obesity, mean age 36.8 [13].
Sources
[1], [2], [5], [12], [13]
Caveats
The umbrella review [12] pools earlier meta-analyses rather than new trials, and rated 3 of its 11 critically low quality. The dieting trial also gave protein, so the effect of HMB alone cannot be separated [13].

Doses studied

The 2024 ISSN position stand reports daily use at 38 mg per kg body weight combined with training [4]. Pooled early safety data came from 9 trials using 3 g a day for 3 to 8 weeks [14]. Two forms have been studied, calcium HMB and free acid HMB; blood levels rose faster with the free acid form in some studies, with mixed recent results [4].

Risks

Reported risks2

LimitedHow often is not known

Disputed trial data

Limited evidence: a published letter documents discrepancies in several HMB free acid papers, which the 2024 ISSN stand says it did not use.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
A published letter documents discrepancies in several papers on HMB free acid and ATP supplementation [15]. The 2024 ISSN stand reports that it did not use the criticized studies to inform its positions [4].
Population
Published trials [15].
Sources
[4], [15]
Caveats
The letter's abstract does not list the specific trials.
ModerateHow often is not known

Industry ties in the evidence base

The 2024 ISSN position stand discloses that its lead author is employed by MTI Biotech and that several authors hold HMB patents. Independent reviews in trained people found no effect.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
The 2024 ISSN position stand discloses that its lead author is employed by MTI Biotech and was a principal investigator at Metabolic Technologies, which marketed HMB-Ca and HMB-FA, and that several authors are listed inventors on HMB patents [4].
Population
Position stand authorship [4].
Sources
[4]
Caveats
Disclosure does not show the findings are wrong. Independent meta-analyses in trained people found no effect [1][2].

Checked, no increase found1

Limited

Adverse effects in early trials

Limited evidence: 9 short trials at 3 g a day found no change in blood chemistry or blood counts.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Across 9 studies giving 3 g a day for 3 to 8 weeks, HMB did not change blood chemistry or hematology markers. Total cholesterol fell 5.8%, LDL 7.3% and systolic pressure 4.4 mmHg against placebo [14].
Population
Men and women, young and old, exercising or not [14].
Sources
[14]
Caveats
A pooled summary of nine trials, not a systematic review. No independent review of long-term safety was located.

Claims tested and not found

  1. That HMB builds muscle or strength in trained people. Six RCTs in athletes and 11 in young lifters found no change in strength or fat-free mass [1][2].
  2. That HMB adds to exercise in older adults. Fat-free mass did not change when HMB was combined with exercise (ES 0.06) [5]. In 13 RCTs, HMB added to resistance training did not change fat mass, muscle mass or strength [9].
  3. That HMB on its own causes fat loss. Fat mass did not change in pooled trials of athletes, young lifters or older adults [1][2][5][12].

Sources

  1. Sanchez-Martinez J, Santos-Lozano A, Garcia-Hermoso A, et al. Effects of beta-hydroxy-beta-methylbutyrate supplementation on strength and body composition in trained and competitive athletes: A meta-analysis of randomized controlled trials. Journal of Science and Medicine in Sport. 2018. https://doi.org/10.1016/j.jsams.2017.11.003
  2. Jakubowski JS, Nunes EA, Teixeira FJ, et al. 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. 2020. https://doi.org/10.3390/nu12051523
  3. Holland BM, Roberts BM, Krieger JW, et al. Does HMB Enhance Body Composition in Athletes? A Systematic Review and Meta-analysis. Journal of Strength and Conditioning Research. 2019. https://doi.org/10.1519/jsc.0000000000003461
  4. Rathmacher JA, Pitchford LM, Stout JR, et al. International society of sports nutrition position stand: β-hydroxy-β-methylbutyrate (HMB). Journal of the International Society of Sports Nutrition. 2024. https://doi.org/10.1080/15502783.2024.2434734
  5. Lin Z, Zhao Y, Chen Q. Effects of oral administration of β-hydroxy β-methylbutyrate on lean body mass in older adults: a systematic review and meta-analysis. European Geriatric Medicine. 2020. https://doi.org/10.1007/s41999-020-00409-9
  6. Li N, Chen S, He Y, et al. Effects of oral supplementation of β-hydroxy-β-methylbutyrate on muscle mass and strength in individuals over the age of 50: a meta-analysis. Frontiers in Nutrition. 2025. https://doi.org/10.3389/fnut.2025.1522287
  7. Gu WT, Zhang LW, Wu FH, et al. The effects of β-hydroxy-β-methylbutyrate supplementation in patients with sarcopenia: A systematic review and meta-analysis. Maturitas. 2025. https://doi.org/10.1016/j.maturitas.2025.108219
  8. Bear DE, Langan A, Dimidi E, et al. β-Hydroxy-β-methylbutyrate and its impact on skeletal muscle mass and physical function in clinical practice: a systematic review and meta-analysis. American Journal of Clinical Nutrition. 2019. https://doi.org/10.1093/ajcn/nqy373
  9. Wang G, Jawed I, Tufail M, et al. Efficacy of HMB supplementation as an adjunct to resistance training in older adults: a comprehensive meta-analysis. Age and Ageing. 2026. https://doi.org/10.1093/ageing/afag073
  10. García-Alonso A, Sánchez-González JL, Navarro-López V, et al. 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. Nutrients. 2025. https://doi.org/10.3390/nu17223624
  11. Rahimi MH, Mohammadi H, Eshaghi H, et al. The Effects of Beta-Hydroxy-Beta-Methylbutyrate Supplementation on Recovery Following Exercise-Induced Muscle Damage: A Systematic Review and Meta-Analysis. Journal of the American College of Nutrition. 2018. https://doi.org/10.1080/07315724.2018.1451789
  12. Bideshki MV, Behzadi M, Jamali M, et al. 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. 2025. https://doi.org/10.1002/jcsm.13671
  13. Jiang J, Liang Y, Wang R, et al. Calcium Beta-Hydroxy-Beta-Methylbutyrate-Enriched Nutritional Supplementation During Dietary Weight Loss in Adults With Obesity: A Randomized Controlled Trial. Journal of Cachexia, Sarcopenia and Muscle. 2026. https://doi.org/10.1002/jcsm.70343
  14. Nissen S, Sharp R, Panton L, et al. β-Hydroxy-β-Methylbutyrate (HMB) Supplementation in Humans Is Safe and May Decrease Cardiovascular Risk Factors. Journal of Nutrition. 2000. https://doi.org/10.1093/jn/130.8.1937
  15. Gentles JA, Phillips SM. Discrepancies in publications related to HMB-FA and ATP supplementation. Nutrition and Metabolism. 2017. https://doi.org/10.1186/s12986-017-0201-7

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