HMB
Reduces muscle breakdown, particularly useful during caloric restriction.
What is HMB?
HMB is a metabolite of the amino acid leucine, produced when your body breaks down protein. It is found naturally in small amounts in certain foods including catfish, grapefruit, and alfalfa. It works primarily by reducing muscle protein breakdown (proteolysis) rather than directly increasing synthesis, which makes it particularly relevant during periods of training while dieting.
What does the evidence say?
Early research in the 1990s by Nissen et al. showed impressive gains in untrained individuals, but follow-up research in trained athletes has produced mixed results. A 2014 meta-analysis by Wilson et al. found significant effects on lean mass and strength, but critics noted several of the studies were conducted by researchers with financial ties to the supplement. More independent research suggests modest anti-catabolic effects, particularly in older adults and during calorie restriction.
Good evidence from several studies, but with some limitations in size, duration, or methodology.
Dosage guide
| Effective dose | 3g per day |
| Maximum dose | 3g per day (higher doses show no additional benefit) |
| Timing | Split into two or three doses with meals. |
Best form to buy
HMB-FA (free acid form) absorbs faster than HMB-Ca (calcium salt). The free acid version is more expensive but better studied in recent trials.
Who benefits most
Men over 40 who are cutting weight while trying to maintain muscle, or those returning to training after a long break. Less compelling for well-trained men in a calorie surplus.
Side effects and safety
Very well tolerated. No significant adverse effects reported at standard doses in healthy adults.
“Honest answer: it's not as impressive as early marketing suggested. If you're dieting hard and losing muscle, it's worth adding. If you're in a surplus and training well, creatine and protein are a better use of your money.”