Compound or practice · Supplement
HMB
A leucine metabolite that mainly helps the untrained and the catabolic — largely redundant for seasoned lifters eating enough protein.
- Overall grade
- Grade C
- Last revised
- 2
- graded outcomes
- 0
- references listed
A structured monograph in Prometheus's bundled library. Its grades are the monograph's own reading of the evidence, not a peer-reviewed review.
1 at grade C · 1 at grade D — 2 graded rows
What is known
Each outcome with its grade (how strong the evidence is, A to D), the size of the effect where the entry records one, and how often studies agree.
- Muscle (untrained / catabolic)Evidence grade C
Context-dependent
Smallmixed
- Muscle (trained, adequate protein)Evidence grade D
Little added benefit
Trivialmixed
What is uncertain
Read off the same rows as above. Nothing here is added that the entry does not itself record.
- Thin evidence: Muscle (untrained / catabolic) (grade C); Muscle (trained, adequate protein) (grade D).
The evidence in words
What it is
HMB is a metabolite of the amino acid leucine marketed for muscle preservation and growth.
How it works
It appears to reduce muscle-protein breakdown, which matters most when breakdown is high — detraining, illness, caloric deficit, or the untrained state.
What the evidence shows
Benefits show up mainly in novices, older adults, and catabolic conditions (bed rest, illness). In trained lifters with adequate protein, effects are small to negligible, and a few extraordinary-effect studies have not replicated. Safe but oversold for the gym crowd.
How to use it
3 g/day, split; the free-acid form is absorbed faster.
Safety & interactions
Well tolerated.
Bottom line
Useful for the untrained, the elderly, and muscle-preservation during illness or dieting; skip it if you're a trained lifter hitting your protein.
How it is used
As the entry records it, from the studies it summarises. Not a recommendation for you — doses that suit a trial population may not suit you.
- Standard
- 3 g/day, split.
Related reading
Entries that share this one's tags or conditions.
- HMB for Muscle (trained, adequate protein)Evidence grade D — Little added benefitEvidence grade D
- HMB for Muscle (untrained / catabolic)Evidence grade C — Context-dependentEvidence grade C
- HMB: dosage and how to take it3 g/day, split.Evidence grade C
- HMB: side effects, safety & interactionsWell tolerated.Evidence grade C
Sources
This entry lists no references of its own.
Last revised . A grade is this entry's reading of the evidence, not medical advice.