Retatrutide and Bodybuilding: Body Composition Data

Evidence-based review of retatrutide body composition data including fat loss, lean mass, and relevance to bodybuilding. DXA scan results from Phase 2.

Retatrutide and Bodybuilding: Body Composition Data — Evidence-based review of retatrutide body composition data including fat loss, lean mass, and relevance to bodybuilding. DXA scan results from Phase 2.

Retatrutide has generated significant interest in the bodybuilding and fitness community due to its triple receptor profile (GIP/GLP-1/glucagon), the largest mean weight reductions reported in any late-stage obesity trial, and the theoretical metabolic advantages conferred by glucagon receptor agonism. Phase 2 DXA body composition data, published by Coskun and colleagues in The Lancet Diabetes & Endocrinology (2025), provide the most detailed look at how retatrutide affects fat mass, lean mass, and regional fat distribution.

The data show substantial fat loss with a lean mass preservation profile roughly comparable to other incretin-based obesity therapies. However, retatrutide is an investigational drug — not approved, not available in clinical-grade form, and associated with significant adverse events including a dysesthesia signal affecting up to 20.9% of participants at the highest dose.

This article presents the clinical evidence. It does not endorse off-label use of any investigational compound.

The bodybuilding community’s interest in retatrutide centers on several pharmacological properties that distinguish it from other incretin-based therapies:

These pharmacological features have made retatrutide a topic of widespread discussion in bodybuilding forums, YouTube channels, and fitness media. However, the clinical data tell a more nuanced story than the enthusiasm might suggest.

The most informative dataset on retatrutide’s effects on body composition comes from a DXA substudy within the Phase 2 trial, published by Coskun and colleagues in The Lancet Diabetes & Endocrinology in 2025.