DEXA may have overstated GLP-1 muscle loss

Earlier human trials had put about 40 percent of GLP-1 weight loss into lean mass, compared with about 25 percent for lifestyle-only weight loss. But the new read on that split is that the measurement tool was muddying the picture, since DEXA scans do not cleanly separate functional muscle from organ tissue like the liver.

The 2026 study in Cell Reports Medicine says that helps explain why the numbers looked so rough. In animal models, a 20 percent drop in lean mass was mostly tied to lower liver weight, not muscle breakdown. The human trial followed the same pattern: muscle cross-sectional area went down, but baseline grip strength and leg strength stayed intact.

That leaves the headline concern looking a lot less straightforward. Muscle biopsies in the newer data pointed to only a 10 percent loss in actual functional tissue, while a separate meta-analysis found GLP-1 users losing muscle at the same rate as patients relying only on caloric restriction.