New Study Raises Questions About How Ozempic Affects Muscle Size and Strength
Media Contact:
Kylene Metzger
Media Relations Manager, Public Affairs, 麻豆学生精品版
Email: Kylene.Metzger@hsc.utah.edu
As use of the popular anti-diabetic and weight-loss drug Ozempic skyrockets, so have concerns about the medication鈥檚 side effects. One such side effect is loss of 鈥渓ean mass鈥濃攂ody weight that isn鈥檛 fat鈥攔aising concerns that Ozempic could be reducing muscle mass and strength.
New research in mice suggests that muscle mass changes less than expected, but muscles may still get weaker, pointing out an urgent need for clinical studies to pin down the full effects of the popular medications.
鈥淚f we want to really help the individuals who may be losing muscle mass, then we need to know that they're actually losing muscle mass,鈥 says , associate professor of nutrition and integrative physiology in the University of Utah College of Health and the senior author on the study. 鈥淲e have data in mice that suggest that things are not as straightforward as they might seem.鈥
Key points:
- Ozempic can cause loss of lean mass, often assumed to be muscle mass.
- A study in mice on Ozempic found less muscle mass loss than expected.
- Muscles may get weaker even when muscle mass is unchanged.
IMPACT: Clinical studies in humans are urgently needed to understand Ozempic鈥檚 side effects.
A weighty concern
Researchers found that Ozempic-induced weight loss did decrease lean mass by about 10%. Most of this lost weight wasn鈥檛 from skeletal muscles but instead from other tissues like the liver, which shrunk by nearly half. The researchers emphasize that more research is needed to determine whether similar changes to organ size occur in humans鈥攁nd whether those changes come with any risks.
鈥淟oss of mass in metabolically active organs, such as the liver, is expected as part of healthy weight loss,鈥 says research instructor in nutrition and integrative physiology at U of U Health and co-first author on the study. In both mice and humans, weight gain and loss can affect the size of organs like the liver without affecting their function. 鈥淚t鈥檚 unlikely that the observed lean mass loss represents a serious adverse effect,鈥 says postdoctoral researcher in the U of U Molecular Medicine Program and co-first author on the study.
Some skeletal muscles did shrink as the mice lost weight鈥攐n average, by about 6%, not enough to explain the overall loss in lean mass. Other muscles stayed the same size.
Some of this loss in muscle mass is a return to baseline, the researchers say. Gains in fat also tend to lead to gains in skeletal muscle, since the body must do more work to move around. So loss of fat can lead to loss of muscle without affecting overall quality of life.
Size isn鈥檛 strength
Interestingly, when the researchers tested the amount of force the mice鈥檚 muscles could exert, they found that, for some muscles, strength decreased as the mice lost weight, even when the size of the muscle stayed roughly the same. For other muscles, strength was unchanged. It鈥檚 unknown how weight loss drugs affect this balance in people, the researchers say.
A potential loss of strength when taking Ozempic may be of particular concern for adults over the age of 60, who are at higher baseline risk for muscle loss and reduced mobility. 鈥淭he loss of physical function is a strong predictor of not just quality of life but longevity,鈥 Funai adds.
Clinical trials are needed
The researchers caution against extrapolating their results directly into humans, because mice and humans gain and lose weight in different ways. In people, obesity is associated with lower physical activity, but mice don鈥檛 tend to become less active when they gain weight. And the mice in this study became overweight because they ate a high-fat diet, whereas people become overweight for a wide variety of reasons that include genetics, diet, sleeping patterns, and age.
Instead of drawing a one-to-one parallel with humans, the researchers say their results emphasize the need for more clinical studies. 鈥淭here remains a significant need for validation in humans, especially concerning muscle strength,鈥 Karasawa says.
Funai adds that clinical trials should check for changes in muscle strength not just for Ozempic but also future weight-loss drugs. 鈥淭here are many additional weight loss drugs that are in clinical trials and coming out in the next three to five years,鈥 Funai says. 鈥淏ut with all those clinical trials, if they鈥檙e interested in measuring lean mass loss, they need to consider physical function.鈥
鈥淥ur findings are really interesting, but this is a preclinical model,鈥 he adds. 鈥淲e need these data in people.鈥
###
The results are published in Cell Metabolism as 鈥溾
This study was supported by the National Institutes of Health, including the National Institute of Diabetes and Digestive and Kidney Diseases (grant numbers DK107397 and DK127979), the National Institute of General Medical Sciences (grant number GM144613), the National Institute on Aging (grant numbers AG074535, AG065993, AG076075, and AG086328), and the National Cancer Institute (grant number CA286584), as well as by the Grant-in-aid for Japan Society for Promotion of Science Fellows (grant number 24KJ2039). Content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.