Lean Body Mass
Everything that isn't fat — muscle, bone, organs — and the thing worth defending during rapid weight loss.
Lean body mass is the engine room: muscle, bone, organs, water. It sets most of your metabolic rate, your strength, and — in later decades — your independence. Any substantial weight loss takes some lean mass along with fat; the clinical concern with large, fast GLP-1-era losses is letting that share drift too high.
Defense is two-pronged and well-evidenced: adequate protein (commonly ~0.7–1 gram per pound of goal body weight daily, a real target when appetite is suppressed) and resistance training a few times weekly, which tells the body its muscle is employed. Patients who run both typically watch composition improve dramatically; patients who run neither can reach goal weight softer and weaker than they intended — same scale number, different outcome.
This glossary entry is general information, not medical advice, and is written to be consistent with FDA prescribing information and primary trial publications as of its last review. Always consult a licensed healthcare provider for personal medical decisions.
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