Review of 1.25 million people finds lean mass loss with GLP-1 drugs, no bone signal

A systematic review and meta-analysis of 60 studies covering 1,250,717 people found that GLP-1 receptor agonists were consistently associated with lower lean body mass, but showed no effect on bone mineral density or fractures at any site. The paper was published in the journal Drugs on September 12, 2026 ^[1].

The authors searched MEDLINE, the Cochrane Central Register of Controlled Trials and Embase from inception to March 2025, screening 1,148 references. They included 46 randomized controlled trials, 13 real-world evidence studies and one pharmacovigilance study ^[1]. The medications represented across those studies were semaglutide, liraglutide, exenatide, dulaglutide, tirzepatide — a dual GIP/GLP-1 agonist — and others ^[1].

The muscle finding came from 28 studies pooled in a random-effects model, with a standardized mean difference of −0.52 (95% confidence interval −0.8 to −0.23) ^[1]. Heterogeneity was high, with an I² of 88% and a p-value for heterogeneity below 0.0001 ^[1]. The result held up in all sensitivity analyses, and no publication bias was found ^[1]. Subgroup analyses showed the effect was mainly driven by liraglutide and semaglutide, and that the decrease in lean body mass or fat-free mass appeared when GLP-1 receptor agonists were compared with placebo ^[1].

Bone outcomes looked different. When the meta-analytic models included the most adjusted effect estimates, the authors observed no effect on bone mineral density at all sites or on fractures at all sites ^[1]. For joints, the models showed no significant change in WOMAC scores for pain, physical function or stiffness ^[1]. The paper describes itself as the first meta-analysis to look at GLP-1 receptor agonists across such a broad panel of musculoskeletal outcomes ^[1].

The authors rated the certainty of the muscle evidence as low and wrote that the lean mass changes "appeared largely related to weight loss" ^[1]. They also flagged a gap in the underlying research: almost no study measured muscle strength or physical performance, so whether the lean mass reductions translate into clinically meaningful problems with muscle function or physical performance "remains uncertain" ^[1]. In the paper's introduction, the authors state that the effects of these drugs on musculoskeletal health "remain completely misunderstood" ^[1].

Why it matters for patients

Lean mass loss is one of the most common worries people raise about this drug class, and this analysis confirms that the drop is a consistent finding across the pooled studies, not a one-off result. At the same time, the same body of evidence did not turn up a signal for lower bone density or more fractures, and the authors stress that the quality of the muscle evidence is low ^[1].

The practical uncertainty is about function, not just mass. The review could not answer whether people taking these drugs lose strength, move less well, or are more likely to fall, because the included studies rarely measured those things ^[1]. A change on a body-composition scan and a change in what a person can physically do are not the same thing, and this paper does not establish that the first leads to the second ^[1].

The analysis also mixes study types — randomized trials alongside real-world and pharmacovigilance data — and the wide confidence interval and high heterogeneity mean the pooled muscle estimate is not precise ^[1]. It does not report results for individual drugs at the level of strength or function, and it does not address who might be at higher risk than others. Those questions have not been answered here.

What happens next

The authors call for further studies that measure muscle function, strength or performance and that use models adjusting for confounding factors ^[1]. The review is registered with PROSPERO under record ID CRD420251024082 ^[1]. No specific follow-up trials, timelines or regulatory actions are described in the paper ^[1].