The rapid rise of GLP-1 weight-loss medicines has transformed obesity treatment, but researchers are increasingly paying attention to an important question: what exactly are patients losing when their body weight falls?
Weight loss does not consist entirely of body fat. Some patients can also lose lean tissue, including muscle, which is particularly important for maintaining strength, mobility and healthy metabolism. This has encouraged pharmaceutical researchers to investigate whether future obesity treatments could help patients lose fat while preserving more muscle.
Regeneron reported mid-stage clinical trial results involving nearly 1,000 adults with obesity. Researchers tested the experimental drug trevogrumab, which inhibits myostatin, a protein involved in regulating muscle growth. It was administered alongside semaglutide, the GLP-1 medicine used in treatments such as Wegovy.
At the selected 75 mg dose, Regeneron reported that trevogrumab preserved more than 70% of the muscle that otherwise would have been lost with semaglutide alone.
This could signal an important change in how the next generation of obesity medicines is evaluated. Instead of focusing almost entirely on the percentage of body weight lost, researchers may increasingly examine body composition—how much fat is lost compared with muscle.
Muscle preservation could be particularly significant for older adults, who naturally become more vulnerable to age-related muscle loss. However, trevogrumab remains experimental, and further studies are required to determine its long-term safety and clinical benefits. h
