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Weight loss drug found to be able to shrink heart muscle in mice and human cells
Last reviewed: 02.07.2025
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Trendy weight-loss drugs that have been touted for their ability to shrink waistlines may also shrink the heart and other muscles, according to a new University of Alberta study published in the journal JACC: Basic to Translational Science. The authors say the study should serve as a “cautionary lesson” about the potential long-term health effects of these drugs.
"If these drugs were prescribed by a doctor, the benefits likely far outweigh the risks," said Jason Dyck, lead author of the study and a professor of pediatrics in the School of Medicine and Dentistry and a member of the Institute for Research on Women's and Children's Health.
"However, the growing number of people who take these drugs without indications and real risks need to be aware of a different risk-benefit balance."
Dyke and his team studied why one of the side effects of the weight loss drug Ozempic is loss of skeletal muscle mass.
Ozempic (semaglutide) was originally developed to help adults with type 2 diabetes control their blood sugar levels. However, the drug and a number of other drugs in its class are being heavily marketed as effective in combating obesity.
Main results of the study
The researchers conducted experiments on mice and found that the heart muscle was reduced in both obese and lean mice. This systemic effect was confirmed in cultured human heart cells.
While Dyke's team did not observe any detrimental functional effects on the hearts of the mice with reduced sizes, he cautions that negative effects could arise in the long term or under certain stresses on the heart.
"Given the growing number of people taking this drug without cardiovascular disease or obesity, we recommend careful evaluation of cardiac structure and function in clinical trials," Dyck said.
Losing Muscle Mass When Losing Weight
Dyke's research comes after a commentary was published in the November issue of The Lancet by an international team of researchers from the University of Alberta, McMaster University and Louisiana State University. The commentary discussed evidence that up to 40% of the weight people lose when using weight-loss drugs is muscle.
Carla Prado, a nutrition researcher and lead author of the commentary, explains that this rate of muscle loss is significantly higher than that seen with typical calorie-restricted diets or natural aging. It can lead to a number of long-term health problems, including decreased immunity, increased risk of infections, and poor wound healing.
"Muscles do much more than just help us move or lift weights. They are powerful organs that keep us healthy in many ways," Prado says.
Recommendations for maintaining muscle mass
To minimize muscle loss while losing weight, Prado recommends focusing on two main areas: nutrition and exercise.
- Nutrition: Ensure adequate intake of high-quality protein, essential vitamins and minerals, and other muscle building blocks. In some cases, protein supplements may be necessary.
- Exercise: Focus on strength training, such as lifting weights or using resistance bands. These exercises help prevent muscle breakdown and maintain strength.
Conclusions
For those using weight loss drugs, Prado recommends following a balanced program that includes proper nutrition and strength training. This allows you to lose fat while minimizing muscle loss and get the most out of your treatment while staying strong and healthy.