Recent research indicates that popular weight loss medications, like Ozempic and Wegovy, may have effects beyond just fat reduction, raising questions about muscle strength and organ size following significant weight loss.
At the University of Utah, scientists studied Semaglutide, a key ingredient in these weight loss drugs, using mice as their subjects.
Published in the journal Cell Metabolism, the researchers noted “unexpected effects,” indicating that around 10% of the weight loss was not fat. A significant portion came from non-muscular tissue, with the liver shrinking nearly by half. Some skeletal muscles saw around a 6% reduction in size, while others remained constant.
Even though the muscle size changes were relatively small, some muscles became weaker. This development is particularly concerning for individuals aged 60 and older, who are already at an increased risk of muscle loss and mobility issues.
“Loss of physical function is a powerful predictor of both quality of life and longevity,” stated Katsu Huyai, a senior author of the study.
These findings challenge the belief that lean mass loss is mostly due to skeletal muscle, highlighting instead the impact on metabolically active organs like the liver, which can shrink during healthy weight loss without losing functionality.
“The observed loss of fat lean mass is unlikely to represent a serious adverse effect,” commented Takuya Karasawa, a co-author.
However, the researchers emphasize the need for further studies in humans to assess whether these effects manifest similarly and whether they pose any health risks.
“There’s still more to test in humans, especially regarding muscle strength,” Karasawa added.
They suggest that upcoming clinical trials should monitor not just lean mass but also muscle strength and physical function, particularly as new weight loss drugs are set to hit the market soon.
As Funai pointed out, “I’m involved in clinical trials, and numerous additional weight loss medications will be introduced in the next 3-5 years. If you’re measuring lean mass loss in these trials, physical function must also be taken into account.”
