HMB (β-hydroxy β-methylbutyrate)
Leucine metabolite with meta-analysis signal for preserving muscle mass in older adults and during bed-rest or unloading.
Why
β-Hydroxy β-methylbutyrate (HMB) is a leucine catabolite: a small percentage of dietary leucine is converted to HMB endogenously. Meta-analyses of HMB supplementation in older adults report modest preservation of lean body mass, particularly during bed-rest, immobilisation, or in sarcopenic states. Effect in young trained athletes is small but present in some meta-analyses. HMB-Ca and HMB free acid are the two main forms; free acid has faster absorption kinetics.
How it works
Inhibits muscle protein breakdown via attenuation of the ubiquitin-proteasome pathway, with modest stimulation of protein synthesis via mTOR. Different mechanism profile from leucine itself: primarily antimisbalance during muscle stress rather than maximal hypertrophy driver.
Expected onset · Lean mass changes over 8–12 weeks; muscle-stress protection effect acute
How to take
Dosage
3 g/day total, often divided. Bed-rest or sarcopenia trials use 3 g/day for 8–10 weeks.
Timing
Divided 2–3 times daily with food
On the label
'Calcium HMB' or 'HMB free acid' (faster absorption) with stated grams. Combine with adequate dietary protein for the muscle-preservation indication.
Ideal for
Older adults at risk of sarcopenia; adults during bed-rest, illness, or immobilisation; cancer-cachexia adjunct under oncology supervision.
Safety
Evidence
Wu 2015 Arch Gerontol Geriatr meta-analysis (7 RCTs, n=287 older adults): HMB 3 g/day preserved lean body mass by ~0.35 kg vs control across 8–12 weeks. Deutz 2013 Clin Nutr RCT in bed-rest model: HMB attenuated bed-rest-induced lean mass loss in older adults. Effect modest but consistent in older / unloading contexts.
- Wu et al., Arch Gerontol Geriatr 2015, effect of beta-hydroxy-beta-methylbutyrate supplementation on muscle loss in older adults: meta-analysis
- Deutz et al., Clin Nutr 2013, effect of beta-hydroxy-beta-methylbutyrate on bed-rest-induced muscle wasting in healthy older adults (RCT)
- Holecek, J Cachexia Sarcopenia Muscle 2017, beta-hydroxy-beta-methylbutyrate supplementation and skeletal muscle in healthy and muscle-wasting conditions (review)
Where to get it
Shop HMB (β-hydroxy β-methylbutyrate) on AmazonSponsored · As an Amazon Associate, Healicus earns from qualifying purchases.