Hydroxy-beta-Methylbutyrate (HMB) is a metabolite of the amino acid Leucine. It is strongly associated with a variety of performance enhancing attributes, in particular gains in lean muscle mass and reductions in fat tissue.
Let’s take a look and see if the research supports the hype.
As different studies use different research methods, summarising the findings can be difficult.
The table below shows a summary of the findings of various studies. At a glance we can see the types of individuals involved, duration and dosage of HMB, and changes in body composition:
[table]Subjects, Duration/dose (per day), Body composition change,
American footballers (NCAA), 7 weeks / 3 grams, FFM +1.9% FM -0.5%,
18-22 yr old males, 3 weeks / 1.5 – 3 grams, FFM +0.6% FM no effect,
18-22 yr old males, 3 weeks / 3 grams, FFM +0.6% FM -0.7%,
18-22 yr old males (resistance trained), 4 weeks / 3 – 6 grams, LBM no effect FM no effect,
18-22 yr old males, 8 weeks / 3 – 6 grams, FFM +3% FM -1.6%,
18-22 yr old males, 12 weeks / 3 grams, LBM +40% FM -40%,
Key: FFM (fat free mass); FM (fat mass); LBM (lean body mass)
As you can see, HMB has consistently been shown to positively affect body composition. This is not just by increasing lean muscle mass but also contributing towards fat tissue reduction.
All the subjects engaged in resistance training programmes throughout the investigation. The only study which showed no effects involved an un-supervised training regime.
We believe that HMB leucine supplements can significantly increase lean muscle mass and decrease fat mass, when used in conjunction with a structured resistance training programme. The research available to us confirms this.
After evaluating the research it seems likely that a dose of 38mg/kg body mass is recommended to achieve such changes in body composition. For example, a 75kg individual should take 2.85g of HMB per day.
Nissen et al (1996) Effect of leucine metabolite beta-hydroxy-betamethylbutyrate on muscle metabolism during resistance-exercise training. J Appl Physiol
Jowko et al (2001) Creatine and beta-hydroxy-beta-methylbutyrate (HMB) additivelyincrease lean body mass and muscle strength during a weight-trainingprogram. J Nutrition
Kreider et al (1999) Effects of calcium betahydroxy-beta-methylbutyrate (HMB) supplementation during resistancetraining on markers of catabolism, body composition and strength. Int J Sports Med
Gallagher et al (2000) Betahydroxy-beta-methylbutyrate ingestion, part I: effects on strength and fat free mass. Med Sci Sports Exerc
Panton et al (2000) Nutritional supplementation of the leucine metabolite beta-hydroxy-beta-methylbutyrate (hmb) during resistance training. J Nutrition