The Mythology: Anticatabolic supercompound, increases strength and muscle mass. Decreases fat.
The Truth: Noobs may benefit with minor strength gains in the lower body. Body comp changes mostly a pipe dream.
Research: HMB or beta-hydroxy beta-methylbutyrate is a by-product of the essential amino acid leucine, proposed to influence muscle protein metabolism and cell membrane integrity.
HMB is claimed to influence strength and lean body mass1.2. by acting as an anticatabolic agent, minimizing protein breakdown and damage to cells that may occur with intense exercise. Research shows that previously untrained men may benefit from HMB supplementation, in terms of minor gains in strength.5.6. Evidence for gains in lean mass or fat loss are less awesome both in trained and untrained individuals with more nays that yeas.
Also for unknown reasons, strength gains are mostly confined to the lower body, which together with the findings in untrained men, suggest that lesser trained muscle groups may benefit the most.
The bad news is that resistance trained athletes will have very little to no gain from HMB both in terms of strength and in terms of changes in body composition. 3.4.
Read it and weep boys.
References 1. Kreider, RB, Ferreira, M, Wilson, M, and Almada, AL, Int J Sports Med 20: 503-509, 1999, Effects of calcium ?-hydroxy-?-methylbutyrate (HMB) supplementation during resistance-training on markers of catabolism, body composition and strength.
2. Ransone, J, Neighbors, K, Lefavi, R, and Chromiak, J, J Strength Cond Res 17: 34-39, 2003, The effect of ?-hydroxy ?-methylbutyrate on muscular strength and body composition in collegiate football players.
3. Slater, G, Jenkins, D, Logan, P, Lee, H, Vukovich, M, Rathmacher, JA, and Hahn, AG, Int J Sport Nutr Exerc Metab 11: 384-396, 2001. ß-Hydroxy-ß-methylbutyrate (HMB) supplementation does not affect changes in strength or body composition during resistance training in trained men.
4. Thomson, Jasmine S; Watson, Patricia E; Rowlands, David S, Journal of Strength and Conditioning Research23. 3 (May 2009): 827-35, Effects of nine weeks of beta-hydroxy-beta- methylbutyrate supplementation on strength and body composition in resistance trained men.
5. Gallagher, PM, Carrithers, JA, Godard, MP, Schulze, KE, and Trappe, SW, Med Sci Sports Exerc 32: 2109-2115, 2000, ?-Hydroxy-?-methylbutyrate ingestion, part I: effects on strength and fat free mass.
6. Jówko, E, Ostaszewski, P, Jank, M, Sacharuk, J, Zieniewicz, A, Wilczak, J, and Nissen, S,Nutrition 17: 558-566, 2001, Creatine and ?-hydroxy-?-methylbutyrate (HMB) additively increase lean body mass and muscle strength during a weight-training program.
How it works: It has been suggested that HMB may attenuate training-induced proteolysis in the muscle via downregulation of proteolytic pathways. In its metabolised form it may provide a carbon source for cholesterol synthesis in the muscles, which in turn provides material for muscle cell growth. HMB may also undergo polymerization and be used as a structural component of the muscular cell membrane, leading to enhanced stability. HMB has been proposed to increase muscle cell fatty-acid oxidation capacity via unknown mechanisms, leading to decreases in fat mass.
Adverse effects: No adverse effects reported to date.