Essential
- Ozempic can lead to a loss of lean mass.
- Some muscles weaken after weight loss linked to Ozempic and others not.
- After this research on mice, clinical studies on humans are necessary to assess the effects of Ozempic on muscles.
What if the Ozempic, an anti -diabetic drug also used as a weight loss treatment, caused muscle to lose, in addition to weight loss? This could be one of the potential side effects of the drug in view of the results of several studies carried out in recent years.
Researchers from University of Utah Health wanted to know more about this phenomenon. They discovered that the Ozempic can lead to a loss of lean mass, often considered as muscle mass. In addition, some muscles are likely to weaken, even if their size has not changed.
Their results were published in the journal Cell MetabolismAugust 5, 2025.
Ozempic: loss of lean mass and strength for certain muscles
To understand the effects of the Ozempic on the muscles, the team observed obese mice treated with the drug. They found that weight loss induced by the drug has led to a reduction of around 10 % of lean mass, generally considered to be muscle mass. “Most of this loss did not come from skeletal muscles, but other fabrics like the liver, whose size has decreased by almost half”specify the authors in their press release. If this loss is mainly linked to a decrease in the size of the organs, some skeletal muscles also founded as the mice lost weight: on average, about 6 %. Others remained of the same size.
The loss of mass of organs or muscles during a healthy thinning is not necessarily worrying for researchers. “Part of this loss of muscle mass corresponds to a return to normal, they explain. Gras mass gains also tend to cause skeletal muscle gains, because the body must provide more efforts to move. Thus, loss of fat mass can cause muscle loss without affecting the quality of global life.”
However, they observed another phenomenon by testing the muscular strength of rodents. For some muscles, the force decreased as the mice lost weight. And that, even when the size of the muscle remained significantly the same. For other muscles, the force remained unchanged.
However, a potential decrease in force can be particularly worrying in seniors who have a higher initial risk of muscle loss and reduced mobility. “The loss of physical function is a reliable indicator not only of the quality of life, but also of longevity”recalls Dr Katsu Funai, principal author of the study.
Muscle loss and muscle loss: you must check the effects on humans
If these results are interesting, the team warns against any direct extrapolation to humans. “Mice and humans gain and lose weight in a different way, indicate the authors. In humans, obesity is associated with less physical activity, but mice do not tend to become less active when they gain weight. In addition, the mice of this study have become obese due to a food rich in fats, while human obesity is due to various reasons: genetics sleep habits and age. “
Thus, for researchers, it is essential to conduct clinical trials to determine whether humans can have adverse effects – especially concerning loss of strength – similar to rodents. It would also be necessary to assess the evolution of muscle strength for all weight loss treatments, according to them. “Many other weight loss drugs are currently on clinical trials and will be marketed in the next three to five years”explains Dr Funai. “But with all these clinical trials, if you want to measure the loss of lean mass, you have to take physical function into account.”