HMB: What It Is and Who Might Benefit

HMB (beta-hydroxy beta-methylbutyrate) is a compound the body naturally produces from the amino acid leucine, and it's sold as a standalone supplement marketed for reducing muscle protein breakdown, particularly during periods of intense training or a calorie deficit.

The research on HMB is mixed: some studies show a modest benefit for untrained individuals just starting a resistance-training program, or for people training in a significant calorie deficit, but the effect appears smaller — often negligible — for already well-trained athletes eating adequate protein.

For most people already meeting their protein needs through food, HMB is unlikely to add much on top of that. It may be worth discussing with a sports dietitian specifically for someone training hard in a sustained calorie deficit, but it isn't a substitute for adequate total protein intake, which remains the more important factor.