HMB (Beta-Hydroxy Beta-Methylbutyrate)

Good evidence for reducing muscle loss in catabolic states and untrained individuals; minimal additional benefit for well-trained athletes already consuming adequate protein.

A rough internal score reflecting quantity, quality, and consistency of human evidence. Not a clinical recommendation.

Meta-analyses support HMB for reducing muscle damage markers and preserving lean mass during caloric restriction or in elderly populations. Benefits in trained athletes are inconsistent and generally small. The free acid form may be better absorbed than calcium HMB.

• Reduces muscle protein breakdown during catabolic states
• May preserve lean mass during caloric restriction
• Supports recovery in untrained individuals beginning exercise

Standard dose is 3 g daily, split into 1 g three times daily. Free acid form (HMB-FA) may be taken 30-60 minutes before exercise.

• Very well-tolerated
• Rare mild GI discomfort

Generally very safe. Some concern about a 2014 study showing implausibly large effects, which has been questioned methodologically.

Most impressive results are in untrained, elderly, or catabolic populations. Trained athletes consuming adequate leucine/protein see diminished returns.

• Muscle50
• Recovery50
• Weight loss30