Does the weight loss drug semaglutide shrink the heart? Scientists offer suggestions →

Compiled by: Gong Zixin

"Magic weight loss drug" semaglutide

Originally developed to help adults with type 2 diabetes

Designed to control blood sugar

However

It is similar to drugs

Touted for its effectiveness in fighting obesity

Will using it to lose weight affect health?

Recently, a new study published in the journal JACC: Basic to Translational Science by the University of Alberta in Canada showed that GLP-1 receptor agonist weight loss drugs (including semaglutide) may cause atrophy of the human heart and other muscles.

"An increasing number of people may be taking these medications who may not meet the eligibility criteria but should be aware of this," said Jason Dyck, senior author of the study, Canada Research Chair in Molecular Medicine and director of the Centre for Cardiovascular Research.

To explore why the main side effect of the weight loss drug Ozempic is skeletal muscle loss, Dyck and his team used mice to study and found that after using semaglutide, the myocardium of both obese and lean mice decreased. Both types of mice showed a decrease in left ventricular mass and total heart weight, as well as a decrease in myocardial cell area. Similar effects were subsequently observed in cultured human heart cells.

The researchers note that no harmful functional effects have been observed in the hearts of mice with shrunken hearts, so no obvious effects on human health are expected. But there may be greater effects in the long term, or some forms of cardiac stress may produce harmful effects that are not observed at rest.

"Given that more and more people without cardiovascular disease or who are not classified as obese are taking this medication, we recommend careful evaluation of cardiac structure and function in ongoing clinical studies of this weight loss medication."

Recently, a review published in the November issue of The Lancet Diabetes & Endocrinology also showed that although GLP-1 receptor agonists are effective for weight loss, they can lead to a large amount of muscle loss. Among the weight lost by people who used weight loss drugs for 36-72 weeks, muscle loss accounted for as much as 25%-39%.

This rate of muscle decline is significantly higher than what occurs with a low-calorie diet or normal aging, and could lead to a range of long-term health problems, including weakened immunity, increased risk of infection and poor wound healing, explained Carla Prado, lead author of the review and a researcher in the Department of Agricultural, Food and Nutritional Sciences at the University of Alberta in Canada.

"Muscle does much more than just help us move or lift things, it's a powerful organ that keeps us healthy in many ways." For example, muscle stores important amino acids, which the body uses to repair itself and stay strong when someone is sick, stressed or injured. It also plays an important role in controlling blood sugar, helping to prevent diabetes.

Prado also notes that muscles release special molecules called myokines, which signal the rest of the body to help fight infection and support the immune system.

“That’s why it’s so important to maintain muscle, especially during weight loss treatment—not just to stay strong, but to keep your entire body resilient and healthy.”

The review authors suggest that muscle loss due to weight loss may exacerbate conditions such as sarcopenic obesity (characterized by a combination of high body fat and low skeletal muscle mass) and lead to worse health outcomes, including cardiovascular disease and higher mortality. While the short-term effects of muscle loss on strength and function are unclear, the review calls for future research to explore how muscle mass loss improves muscle quality and composition.

Scientific advice:

Prado points out that in order to keep your muscles strong while losing weight, you have to focus on two things: nutrition and exercise.

Proper nutrition means getting enough high-quality protein, essential vitamins and minerals, and other "muscle-building" nutrients. Sometimes, protein supplements can be included to ensure the body has the nutrients it needs.

“Exercise is just as important — especially resistance training like lifting weights or using resistance bands, which helps prevent muscle breakdown and maintain strength during weight loss.”

She adds that it's best for anyone using weight loss pills to follow a balanced plan that includes adequate protein and resistance training. "This can help people lose fat while minimizing muscle loss to gain the health benefits of the treatment and stay strong."

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