Preserves Lean Mass Enhances Recovery A Dietary Supplement Vegetarian/Vegan Non-GMO GMP Quality Assured HMB (B-Hydroxy B-Methylbutyrate) is a clinically researched, naturally occurring metabolite of the branched-chain amino acid leucine. HBM normally plays a role in the regulation of protein breakdown in the body, helping to preserve lean muscle tissue. HMB therefore can help to maintain muscle strength and mass when combined with regular exercise and a healthy diet. In addition, it may help to enhance recovery from intense exercise.