Grade B
Body-composition change on GLP-1 therapy: what newer evidence actually shows
Newer body-composition evidence published in 2024–2026 has substantially revised the lean-mass story on GLP-1 therapy. Conte, Hall, and Klein (JAMA 2024) quantified the fat-mass to fat-free-mass split at roughly 61/39 on semaglutide, 75/25 on tirzepatide, and 67/33 on retatrutide. The SEMALEAN study (Alissou 2026, semaglutide 2.4 mg, 12 months) showed sarcopenic obesity prevalence fell from 49 percent to 33 percent and handgrip strength improved. The earlier 40 percent practitioner estimate has been retired in favor of these verified numbers. A methodological note matters: DEXA-based 'lean mass loss' includes intramuscular fat, which MRI proton-density fat fraction can separate but DEXA cannot. The clinical priority is unchanged — adequate protein (1.2 to 1.6 g/kg of ideal body weight per day) and progressive resistance training are what determine the body-composition outcome.
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