New research from Vanderbilt Health looked at how modern weight‑loss medicines and weight‑loss surgery change the body. The study found both methods cut a lot of fat while keeping most muscle.
Body makeup matters a lot for health. More fat in the body raises the chance of dying from heart problems and other obesity‑related diseases. More muscle (fat‑free mass) lowers that risk.
So, losing fat is good, but keeping muscle is also very important. Researchers want to learn more about how each treatment affects fat and muscle.
The study examined health records from 1,257 people who had bariatric surgery between 2017 and 2022, and 1,809 people who took the drugs semaglutide or tirzepatide from 2018 to 2023. All participants were 18 to 65 years old. People with severe kidney disease or heart failure were not included.
To measure body makeup, scientists used bioelectrical impedance analysis. This tool estimates fat and lean mass from height, weight, age, race, gender, diabetes history, and how long the drug was used.
After 24 months, both groups showed the same pattern. They lost a large amount of fat and only a small amount of muscle. The ratio of muscle to fat went up, meaning overall body composition improved.
Men tended to keep more muscle over time than women.
The research team included doctors and scientists from many departments. The work was funded in part by National Institutes of Health grants R01DK126721 and R01CA275864.