A new study has found that older adults and women taking the weight-loss drug semaglutide may lose more muscle than others, but eating more protein could help reduce this risk.
The research was presented at ENDO 2025, the Endocrine Society’s annual meeting in San Francisco.
Semaglutide is a type of anti-obesity drug that works by mimicking a hormone called GLP-1. It helps people lose weight by reducing appetite and slowing digestion. However, like many weight-loss methods, it can cause not just fat loss, but also muscle loss — also known as lean mass loss.
Dr. Melanie Haines, the lead researcher from Massachusetts General Hospital and Harvard Medical School, explained that losing muscle during weight loss can hurt your health. Muscle plays a key role in controlling blood sugar and supporting strong bones.
When people lose too much muscle, it may increase the risk of poor metabolism, bone weakness, and even frailty.
In the study, researchers looked at 40 adults with obesity over a three-month period. Of the group, 23 were prescribed semaglutide, while the remaining 17 followed a lifestyle and diet plan called Healthy Habits for Life (HHL). The researchers measured how much muscle mass participants lost as they lost weight.
The results showed that people taking semaglutide lost more weight overall than those in the HHL group. But in both groups, about 40% of the weight lost came from lean mass, including muscle. This confirms that muscle loss is a common side effect of weight loss, regardless of how the weight is lost.
However, the study also found that certain people lost more muscle than others. In the semaglutide group, women, older adults, and those who ate less protein lost more muscle. Furthermore, people who lost more muscle showed less improvement in their blood sugar levels, as measured by HbA1c — a marker used to assess long-term blood sugar control.
This finding is important because semaglutide is often used to help people with obesity not only lose weight but also manage conditions like type 2 diabetes. If losing too much muscle reduces the drug’s benefits on blood sugar control, then it’s important to find ways to preserve muscle during treatment.
Dr. Haines says that increasing protein intake might be one way to protect muscle while using semaglutide. This could help keep the positive effects of weight loss, like improved blood sugar levels, without some of the downsides.
She also emphasized the need for more research. Future studies are needed to discover the best strategies for helping people lose fat but keep their muscle when using GLP-1 medications like semaglutide. These strategies could be especially important for women and older adults, who appear to be at greater risk of muscle loss.
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