Beta-hydroxy beta-methylbutyrate, or HMB for short, is a metabolite of the branched-chain amino acid (BCAA), leucine.

Approximately 5% of leucine is naturally converted to HMB, appears to reduce muscle breakdown (catabolism). HMB is also found naturally occurring in foods like alfalfa, grapefruit and certain types of fish.

As a supplement, HMB can function as an anti-cataoblic agent, to positively influence performance and recovery. It’s not usually categorised as an anabolic supplement, as its role in muscle protein synthesis is said to be limited. Because of this, it may not promote muscle mass by its own merit. However, research suggests it may enhance muscle cell structure, and help to limit damage to cell membranes. HMB is also required to synthesise cholesterol, which helps to maintain integrity of the muscle cells. It’s these attributes combined that may exhibit powerful effects in terms of maintaining muscle mass.

Since HMB is a metabolite of leucine, it has been questioned whether extra HMB is necessary. Since the natural conversion rate is low, it’s believed that a supplement can offer greater use than leucine alone.

If you’re following an intense exercise regime, HMB can be of particular benefit. Working consistently will build muscle, but on the other hand, overtraining can cause muscle breakdown \u2013 it’s all about striking the right balance. A good diet is essential, but supplements can help to up the ante; they provide additional support that can be difficult to achieve through food alone. HMB can positively influence your progress by helping to maintain muscle mass.

Losing body fat requires a calorie deficit which can lead to loss of muscle; this too, can negatively impact your results. When slimming down, there is a risk of the body breaking down muscle, in order to source protein. This can happen when fat intake in inadequate, and/or when cardio dominates a fitness routine. Building muscle is anabolic, whereas fat loss is catabolic \u2013 thus, they appear to be opposing goals, though losing mass can also affect fat loss, long-term.


Supplementing HMB can help to lessen the catabolic effects of a calorie-reduced diet, without overly compromising your results. You’ll usually find it in capsule form in around a 500mg dose, designed for daily use.

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