GLP‑1 Weight‑Loss Drugs: Melting Fat at the Cost of Muscle

Publish Date : 07/23/2025

New research is raising alarms: weight-loss injections like Ozempic (semaglutide) and Mounjaro/Zepbound (tirzepatide) may cause dramatic losses in lean muscle mass, even as they shed body fat.

A recent Study Finds report shows that 25–40% of total weight lost on these GLP‑1 drugs comes from muscle, not fat. That is a lot of muscle loss. More importantly, it is not what people expected when the began taking Ozempic, etc.

A small but eye-opening study at the ENDO 2025 conference tracked 40 obese adults: semaglutide users lost more weight overall – roughly 6.3% body weight vs. 2.5% for diet alone – but saw similar muscle loss. Older women and those eating low-protein diets were hardest hit.

This isn’t unexpected: muscle loss often comes with weight loss. But on GLP‑1s it’s worse. A 68‑week trial of semaglutide found users shed around 15 lb of muscle alongside 23 lb of fat. Other sources note similar patterns – nearly 40% of weight reduction in some trials is lean mass.

But experts say it doesn’t have to be this way. Nutrition and exercise – especially resistance training and 1.6 g of protein per kg of body weight daily – can preserve muscle while rebooting metabolism and glucose control.

That balancing act matters: muscle loss can weaken bones, slow metabolism, and reduce daily function – undermining the long-term benefits these drugs promise.

GLP‑1s like Ozempic and tirzepatide can be powerful tools – but they’re not a magic bullet. To protect lean mass, users must pair medication with smart protein intake, strength workouts, and regular check-ins with their medical team.

As GLP‑1 prescriptions surge, so should awareness: fat loss doesn’t have to come at the expense of muscle.

Want to find out if you or a loved one has an Ozempic claim?

Please feel free to contact an Ozempic Lawsuit attorney at info@westrikeback.com or 1-877-542-4646. One of our experienced Ozempic Lawsuit lawyers will help evaluate your claim and explain your legal rights for free. McSweeney / Langevin is providing consultations to individuals throughout the United States. Information provided by email or phone will be kept confidential.