HMB
HMB (beta-hydroxy-beta-methylbutyrate) is a substance the body makes from the amino acid leucine. It is mostly studied for muscle preservation.
Also listed as Hydroxy-MethylButyrate, beta-hydroxy-beta-methylbutyrate
Does it add to resistance training?
A 2020 meta-analysis in adults aged 18 to 45 found no significant added improvement in fat-free mass or strength with HMB during resistance training. A small increase in total body weight did not translate into those desired outcomes. 1
For young adults doing resistance training, this analysis does not support an extra muscle or strength benefit. 1
Why do other reviews sound more positive?
A 2025 umbrella review combined 11 meta-analyses across broader adult populations and found small average improvements in muscle mass and strength. The included reviews varied in quality and populations, so this result should not erase the negative finding in young resistance-training participants. 1 2
Do lower muscle-damage markers mean faster recovery?
A 2018 meta-analysis found lower blood concentrations of creatine kinase and lactate dehydrogenase after exercise with HMB. These enzymes are indirect markers of muscle damage. 3
The laboratory signal is worth studying, but it does not by itself show when someone can train comfortably or perform at full capacity again. 3
Effects by health goal
Open an effect to see the studies behind its rating. Bars show the size of the effect; the letter grades the evidence.
Fitness4 effects
No study is linked to this rating.
No study is linked to this rating.
Energy1 effect
No study is linked to this rating.
All studies
6 publications are linked to HMB, newest first.