Study raises questions about how Ozempic affects muscle size and strength

Research in mice suggests that using Ozempic for weight loss could affect muscle mass and strength . Therefore, the authors point to the urgent need for clinical studies to determine the full effects of this type of drug.

The study led by the University of Utah (USA) indicates that one of the drug's side effects is the loss of lean mass (body weight that is not fat) .

Research in mice suggests that muscle mass changes less than expected, but that muscles may still weaken.

Although these results should not be directly extrapolated to humans, as mice and humans gain and lose weight differently, the researchers say they "highlight the need for further clinical studies."

“There is still a significant need for human validation, especially with regard to muscle strength,” according to Katsu Funai of the University of Utah. While the current findings are “really interesting,” they were conducted in mice, and the data needs to be available in humans.

In addition to Ozempic, other weight-loss drugs are in clinical trials and will be on the market in a few years . "If we really want to help people who may be losing muscle mass, then we need to know that they are actually losing muscle mass," the researcher, quoted by the university center, emphasized.

The study, published in Cell Metabolics, indicates that Ozempic-induced weight loss reduced lean mass by approximately 10% , most of it not from skeletal muscle, but from other tissues such as the liver, which was reduced by almost half.

Loss of mass in metabolically active organs, such as the liver, “is something to be expected as part of healthy weight loss,” says Ran Hee Choi, another of the signatories.

Although “the observed loss of lean mass is unlikely to represent a serious adverse effect,” the researchers stressed the need for further research to determine whether similar changes in organ size occur in humans and whether these carry any risks .

The research also notes that some skeletal muscles shrank as the mice lost weight, on average about 6%, which is not enough to explain the overall loss of lean mass.

Increased fat tends to lead to increased skeletal muscle growth , as the body must work harder to move. Therefore, fat loss can lead to muscle loss without affecting overall quality of life.

When the researchers tested the force the mice's muscles could exert, they found that in some muscles, the force decreased as the animals lost weight, even when muscle size remained virtually the same. In other muscles, the force remained unchanged.

How weight-loss drugs affect this balance in people is unknown, researchers say.

Possible loss of strength while taking Ozempic may be of particular concern for people over 60 years of age , who have a higher baseline risk of muscle loss and reduced mobility.

“Loss of physical function is a strong indicator not only of quality of life, but also of longevity,” Funai added.