If you take Ozempic or a similar drug, you may have heard the worry. The weight comes off, which is the point. But along with the fat, you may be giving up something else that is harder to replace.
That something is muscle. New data from a mid-stage trial suggest an experimental antibody can protect most of it.
In a planned imaging substudy, the drug preserved about 70 percent of the thigh muscle that people would otherwise lose while taking semaglutide. Semaglutide is the active ingredient in Novo Nordisk's Ozempic and Wegovy.
The results come from the COURAGE trial, run by US biotech Regeneron. The trial enrolled 975 adults with obesity and ran for 52 weeks.
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The findings were presented at the European Association for the Study of Diabetes meeting in Milan at the start of October 2026 and reported in News Medical. Full results are in press at The Lancet.
Why muscle loss on GLP-1 drugs matters
Weight loss from any method takes some muscle along with the fat. The question is how much.
According to the Endocrine Society, between 15 and 60 percent of the weight people lose on GLP-1 drugs can come from lean mass rather than fat, depending on the person and the drug.
That matters most for older adults, who are already losing muscle with age.
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The society warns that extra muscle loss on top of normal aging can push people toward sarcopenia, a condition that raises the risk of falls, fractures and loss of independence.
What the trial actually measured
The drug in the trial is called trevogrumab. It is an antibody that blocks myostatin, a protein the body uses to limit muscle growth. By releasing that brake during weight loss, the idea is to let more of the muscle stay.
Trevogrumab was tested as an add-on to weekly semaglutide.
The lower-dose arm compared 25 mg and 75 mg of the antibody with semaglutide alone. A planned MRI substudy measured thigh muscle directly, which is more precise than a standard body scan.
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People on semaglutide alone lost thigh muscle volume over the year. With the 25 mg dose of trevogrumab added, about 72 percent of that loss was prevented. With 75 mg, about 69 percent.
What the drug is not yet
Trevogrumab is not approved by the US Food and Drug Administration.
The data so far come from a mid-stage trial designed to show whether the drug does what the company claims, not whether it is safe and effective in everyday use.
Regeneron said it will start a new phase 2 trial of trevogrumab combined with GLP-1 therapy. The next test will focus on older adults with obesity and low muscle mass or strength.
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This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.