Tirzepatide and muscle composition changes in people with type 2 diabetes (SURPASS-3 MRI): a post-hoc analysis of a randomised, open-label, parallel-group, phase 3 trial.
Quick Facts
What This Study Found
In the SURPASS-3 MRI substudy, tirzepatide reduced thigh muscle fat infiltration more than expected from weight loss alone. Muscle volume decreased proportionally to weight loss. Compared to insulin degludec, tirzepatide showed distinct muscle composition changes.
Key Numbers
246 participants analyzed (190 tirzepatide, 56 insulin degludec). Tirzepatide: muscle fat infiltration decreased 0.36 percentage points (p<0.0001). Muscle volume decreased 0.64 L (p<0.0001). Muscle volume Z score decreased 0.22 (p<0.0001). Muscle volume changes matched population-based estimates for weight loss. Fat infiltration reduction exceeded estimates (difference -0.42 pp, p<0.0001).
How They Did This
Post-hoc analysis of the SURPASS-3 MRI substudy. Phase 3, randomized, open-label trial comparing tirzepatide (5/10/15 mg weekly) vs. insulin degludec. Thigh MRI at baseline and week 52. Compared observed changes to UK Biobank population estimates (n=2942).
Why This Research Matters
Weight loss drugs raise concerns about muscle loss. This MRI study suggests tirzepatide's muscle volume changes are typical for the amount of weight lost, and it may actually improve muscle quality by reducing fat within muscle tissue.
What This Study Doesn't Tell Us
Post-hoc exploratory analysis. Open-label design. MRI substudy subset only. Cannot determine if muscle quality improvement translates to functional benefits. Funded by Eli Lilly.
Trust & Context
- Original Title:
- Tirzepatide and muscle composition changes in people with type 2 diabetes (SURPASS-3 MRI): a post-hoc analysis of a randomised, open-label, parallel-group, phase 3 trial.
- Published In:
- The lancet. Diabetes & endocrinology, 13(6), 482-493 (2025)
- Authors:
- Sattar, Naveed(10), Neeland, Ian J(2), Dahlqvist Leinhard, Olof, Fernández Landó, Laura, Bray, Ross, Linge, Jennifer, Rodriguez, Angel
- Database ID:
- RPEP-13439
Evidence Hierarchy
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Cite This Study
https://rethinkpeptides.com/research/RPEP-13439APA
Sattar, Naveed; Neeland, Ian J; Dahlqvist Leinhard, Olof; Fernández Landó, Laura; Bray, Ross; Linge, Jennifer; Rodriguez, Angel. (2025). Tirzepatide and muscle composition changes in people with type 2 diabetes (SURPASS-3 MRI): a post-hoc analysis of a randomised, open-label, parallel-group, phase 3 trial.. The lancet. Diabetes & endocrinology, 13(6), 482-493. https://doi.org/10.1016/S2213-8587(25)00027-0
MLA
Sattar, Naveed, et al. "Tirzepatide and muscle composition changes in people with type 2 diabetes (SURPASS-3 MRI): a post-hoc analysis of a randomised, open-label, parallel-group, phase 3 trial.." The lancet. Diabetes & endocrinology, 2025. https://doi.org/10.1016/S2213-8587(25)00027-0
RethinkPeptides
RethinkPeptides Research Database. "Tirzepatide and muscle composition changes in people with ty..." RPEP-13439. Retrieved from https://rethinkpeptides.com/research/sattar-2025-tirzepatide-and-muscle-composition
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Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkPeptides research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.