Mobility/Weight/Performance

HMB

Leucine metabolite that may help preserve muscle and physical function, especially in older adults or during inactivity.

HMB

Leucine metabolite that may help preserve muscle and physical function, especially in older adults or during inactivity.

score

evidence

Safe

risk

Overview

Forms

Safety

Stack

Quick Take

Best for older adults, beginners, or inactivity periods — modest payoff for healthy trained adults.

HMB (β-hydroxy β-methylbutyrate) is a leucine metabolite made in the body and found in trace amounts in foods such as catfish and some citrus fruit. It appears to reduce muscle protein breakdown and may also support muscle protein synthesis and muscle-cell membrane repair. Best-backed uses are preserving lean mass during aging or inactivity, modestly improving physical function in older or untrained adults, and possibly reducing exercise-related muscle damage.

Proven Benefits

Preserves lean mass

May improve physical function

May reduce muscle damage

May improve strength gains

May improve body composition

May improve aerobic performance

Protocol

Amount

3 g

Frequency

Split into 2-3 doses daily

When

Any time of day — consistency matters more than timing; HMB free acid can be taken 30-60 minutes pre-workout.

Onset Time

2-4 weeks for recovery; 8-12 weeks for lean mass/function

Who Should Consider

Adults 50+ worried about muscle loss

Beginners starting resistance training

Adults returning after a layoff

People facing short periods of inactivity

Adults dieting and trying to keep muscle

Food Sources

Catfish and some citrus fruits (trace amounts only)

How It Works

HMB helps shift muscle balance toward retention by lowering proteolysis through the ubiquitin-proteasome pathway and supporting mTOR-related protein synthesis. It may also help maintain muscle-cell membrane integrity, which can aid recovery after hard training or inactivity.

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