If you’ve spent any time reading about GLP-1s or taking one yourself, you’ve probably heard the incessant warnings that the obesity drugs can cause significant muscle loss. And if you haven't, here's the gist: Medications like Ozempic, Wegovy, and Zepbound can lead to major weight loss, but people are starting to worry that a portion of that weight can come from muscle rather than fat. The thing is, though, the warnings around GLP-1s have made it sound like these medications are uniquely and highly destructive to muscle—but recent research is starting to suggest otherwise.
A small study published this spring in Cell Reports Medicine was one of the first to look at actual muscle size and strength in people taking a GLP-1 (many prior studies looked instead at just lean body mass, which encompasses more than just muscle—more on that, below). Not as worrisome as the headlines led you to believe. Losing some muscle is definitely a valid concern anytime someone loses weight, says study author Henning Langer, PhD, who leads the Muscle Wasting Laboratory at Charité in Berlin, but “there does not seem to be anything particularly negative about the type of weight loss that is achieved via GLP-1 medicines.” Have all the muscle-loss warnings gotten ahead of the science?
Some experts think that’s the case, but that doesn’t mean the concern should be brushed aside. Here’s what you need to know, per the latest research and experts. Meet the experts: Henning Langer, PhD, is a researcher and the head of the Muscle Wasting Laboratory at Charité in Berlin.
Stuart Phillips, PhD, is a distinguished university professor and chair of the department of kinesiology at McMaster University. Mir Ali, MD, is a bariatric surgeon and the medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center. Kushner, MD, is a professor emeritus at Northwestern University Feinberg School of Medicine.
Pooja Gidwani, MD, is an internal and obesity medicine physician. First, some context for where all the GLP-1 muscle loss claims come from: A lot of the alarm around GLP-1s and muscle loss traces back to body composition research, including the STEP 1 semaglutide sub-study from 2021 and the SURMOUNT-1 tirzepatide sub-study from 2025. Both looked at how body composition changed while taking the meds and found that people lost about 10 percent of lean body mass while taking a GLP-1.
The confusion came when lean mass got equated to muscle. Lean body mass is basically everything in your body that isn’t fat, Langer explains. Muscle is part of it, but so are your organs and the water and connective tissue throughout your body.
Extract — continue reading at the source.
