HMB (beta-Hydroxy beta-methylbutyric acid) is a metabolite of the incredibly popular amino acid l-leucine. When leucine metabolizes in the body, about 5% of that converts into HMB, and recent science suggests it is this metabolite that most effectively preserves muscle mass from degradation when calories are low or when training in the gym.

HMB is a controversial ingredient for a lot, as there seem to be as many who swear by it as there are who think it makes more sense to simply use leucine. While no conclusive science has yet to be conducted proving or disproving the efficacy of this ingredient, there is currently enough information available to validate HMB as a potential addition for almost every athlete.

What it does

Studies on HMB suggest it is capable of increased fat loss[1] and rate of muscle recovery[2], and decreases in muscular damage[2][3], and holds potential for the increase in peak power[4].

How it works

HMB has been shown to decrease the 3 major markers of muscular damage, creatine phosphokinase (CK), lactate dehydrogenase (LDH), and 3-methylhistidine (3-MH). By lowering these three important biomarkers, it is theorized that HMB protects muscle mass from degradation during times of low calories and intense exercise.

Although leucine does convert into HMB, the rate is very low. In order to get the same amount of HMB as the suggested daily dosing, one would need to be consuming in the magnitude of 50g+/day of leucine, far beyond what is achieveable from food or almost any dietary supplements.


The most common dosing protocol for HMB is 1-3g/day, usually taken prior to and or during exercise. If being taken during these times, HMB free acid is suggested to exert its potential benefits immediately, while if taken throughout the day, some might suggest HMB-calcium salt.