Ozempic, a drug originally developed for diabetes that has become widely used for weight loss, has been praised for its effectiveness in shedding pounds.
But new research in mice suggests the drug may have unexpected effects on muscles—reducing their strength even when their size stays the same.
The study, published in Cell Metabolism by researchers at the University of Utah, adds nuance to growing concerns about Ozempic and similar drugs causing loss of “lean mass,” which includes everything in the body that isn’t fat, such as muscles, bones, and organs.
Senior author Katsu Funai, Ph.D., says the findings show the situation is more complicated than simply losing muscle mass.
“We have data in mice that suggest things are not as straightforward as they might seem,” he explained.
When the researchers looked at where lean mass was lost in mice treated with Ozempic, they found that most of it didn’t come from skeletal muscles but from other tissues, especially the liver, which shrank by nearly half.
Loss of mass in metabolically active organs, like the liver, often occurs with healthy weight loss and doesn’t necessarily mean the organ is damaged.
Skeletal muscles did shrink slightly—on average by about 6%—but this reduction was not enough to account for the total lean mass lost.
In some cases, muscle size stayed the same. However, when the researchers measured how much force the muscles could produce, some were weaker despite their unchanged size. Others maintained their strength.
This raises a concern that Ozempic might reduce muscle function even without visibly reducing muscle size. For older adults—especially those over 60, who are already at higher risk of muscle loss and reduced mobility—this could be important.
“The loss of physical function is a strong predictor of not just quality of life but longevity,” Funai said.
The researchers caution that results from mice don’t always apply directly to humans. Mice and humans gain and lose weight differently, and in this study, the mice became overweight from a high-fat diet. Human weight gain can result from many factors, including genetics, diet, sleep, and age.
Still, the findings highlight an urgent need for human studies. Future clinical trials, Funai says, should not only measure lean mass changes but also test muscle strength when evaluating Ozempic and other weight-loss drugs currently in development.
“There are many additional weight-loss drugs in clinical trials right now,” Funai said. “If we want to really help people, we need to know whether these treatments affect not just how much muscle you have, but how well that muscle works.”
If you care about diabetes, please read studies about high vitamin D level linked to lower dementia risk in diabetes, and green tea could help reduce death risk in diabetes.
For more information about nutrition, please see recent studies that blueberries strongly benefit people with metabolic syndrome, and results showing vitamin D could improve blood pressure in people with diabetes.
Source: University of Utah.
