Effects of beta-hydroxy-beta-methylbutyrate (HMB) on exercise performance and body composition across varying levels of age, sex, and training experience: A review

Abstract

The leucine metabolite beta-hydroxy-beta-methylbutyrate (HMB) has been extensively used as an ergogenic aid; particularly among bodybuilders and strength/power athletes, who use it to promote exercise performance and skeletal muscle hypertrophy. While numerous studies have supported the efficacy of HMB in exercise and clinical conditions, there have been a number of conflicting results. Therefore, the first purpose of this paper will be to provide an in depth and objective analysis of HMB research. Special care is taken to present critical details of each study in an attempt to both examine the effectiveness of HMB as well as explain possible reasons for conflicting results seen in the literature. Within this analysis, moderator variables such as age, training experience, various states of muscle catabolism, and optimal dosages of HMB are discussed. The validity of dependent measurements, clustering of data, and a conflict of interest bias will also be analyzed. A second purpose of this paper is to provide a comprehensive discussion on possible mechanisms, which HMB may operate through. Currently, the most readily discussed mechanism has been attributed to HMB as a precursor to the rate limiting enzyme to cholesterol synthesis HMG-coenzyme A reductase. However, an increase in research has been directed towards possible proteolytic pathways HMB may operate through. Evidence from cachectic cancer studies suggests that HMB may inhibit the ubiquitin-proteasome proteolytic pathway responsible for the specific degradation of intracellular proteins. HMB may also directly stimulate protein synthesis, through an mTOR dependent mechanism. Finally, special care has been taken to provide future research implications.

Resistance training & beta-hydroxy-beta-methylbutyrate supplementation on hormones

“…), while increases in lean muscle mass, which increases the capacity of the body to produce force, accounts for a greater percentage of strength gain later on 13 . Currently, the ability of HMB to increase indices of strength has been attributed to the changes observed in lean mass.…”

“…Previous studies in adults suggested that the use of this dose resulted in the greatest effects on muscle mass and muscle strength 21 . Also, when supplementing with HMB, current evidence suggests that 1 g of HMB should be consumed three times per day, for a total of 3 g of HMB daily 13 .…”

“…However, recent studies have generated a more concrete basis regarding HMB mechanisms of action 12 . Possible mechanisms of action include reduced muscle damage due to stabilization of muscle cell membrane, modulation of protein degradation by inhibition of the ubiquitin-proteosome system, and upregulation of IGF-1 gene expression in the skeletal muscle, and the mTOR signaling pathway leading to protein synthesis [13][14][15] .…”

Influence of oral administration of HMB to pregnant dams on calbindin expression in the dentate gyrus of the hippocampus during postnatal development in spiny mice offspring

“…β-hydroxy-β-methylbutyrate (HMB) is a leucine metabolite used as a diet supplement in order to improve the efficacy of exercises and to gain skeleton muscle hypertrophy (29,30). It has been demonstrated that prenatal administration of HMB has a positive impact on the growth and development of farm animals (26,27).…”

The effect of HMB supplementation on body composition, fitness, hormonal and inflammatory mediators in elite adolescent volleyball players: a prospective randomized, double-blind, placebo-controlled study

“…HMB exerts its effects through protective, anticatabolic mechanisms and has been shown to directly influence protein synthesis (Slater and Jenkins 2000). Possible mechanisms of action include reduced muscle damage due to stabilization of muscle cell membrane, modulation of protein degradation by inhibition of the ubiquitin-proteosome system, and upregulation of IGF-1 gene expression in the skeletal muscle, and the mTOR signaling pathway leading to protein synthesis (Wilson et al 2008;Zanchi et al 2010).…”