Impact of Semaglutide on Body Composition in Adults With Overweight or Obesity: Exploratory Analysis of the STEP 1 Study

Researchers studied 140 adults with overweight or obesity from a larger 68-week trial. They received weekly semaglutide injections or placebo, meaning inactive injections, along with advice about diet and activity. Whole-body DEXA scans, which use low-dose X-rays to estimate body fat and lean tissue, measured changes. The semaglutide group lost about 15% of their body weight, including 19.3% less fat and 9.7% less lean body mass, which includes muscle and other non-fat tissue. Fat around the organs, called visceral fat, fell by about 27%.

What this means for you: Semaglutide weight loss was mostly fat, but people also lost some lean body mass. This small, exploratory analysis does not show whether people preserved muscle strength or function, so it is not by itself a reason to buy or use the drug.