HMB Supplement Preserves Lean Mass During Dietary Weight Loss

A clinical study found that, during calorie restriction-induced weight loss, a calcium beta-hydroxy-beta-methylbutyrate (CaHMB) supplement helped to preserve muscle mass over placebo. The findings were published in the Journal of Cachexia, Sarcopenia, and Muscle.

HMB, a metabolite of the amino acid leucine, has been a sought-after ingredient in sports nutrition formulations for several years thanks to its role in both muscle repair and maintenance. As attention is placed on the loss of muscle that occurs during both dietary and pharmacologic weight loss, HMB is being considered as a potential nutritional aid to mitigate these losses.

In the randomized, double-blind, clinical study, 102 adults with obesity (37% female) were assigned to a CaHMB-enhanced nutritional supplement or an energy-matched maltodextrin control for 12 weeks, alongside dietary energy restriction supervised by clinicians, based on ideal body weight. Adherence was monitored remotely.

The primary outcome was change in whole-body skeletal muscle mass (SMM), measured by multifrequency bioelectrical impedance analysis. Secondary outcomes included visceral fat area, body fat mass, basal metabolic rate, physical function, and metabolic markers.

The treatment group maintained skeletal muscle mass, with a median gain of +0.7 kg, while the control group lost a median -0.6 kg of skeletal muscle mass. The CaHMB group also produced greater reductions in visceral fat area (-14.9 cm²  versus -4.5) and body fat mass (-4.9 kg versus -3.1). Basal metabolic rate was preserved, and the treatment group saw significantly greater reductions in fasting glucose than control.

“Mechanistically, CaHMB may support muscle protein metabolism by increasing muscle protein synthesis through mTORC1/p70S6K signaling and by reducing protein degradation through inhibition of ubiquitin-proteasome pathways,” the authors noted. “Our findings add to the current literature on CaHMB by extending prior evidence from older adults with sarcopenia, exercise-induced muscle damage, and nutritional strategies during weight loss. In contrast to conventional weight loss interventions, where lean mass commonly accounts for a clinically meaningful proportion of total weight loss, the control group in the trial lost SMM whereas the CaHMB group maintained or gained SMM,” at a magnitude comparable to resistance training.