A powerful new weight-loss drug that has helped millions of people may work in a surprising way, according to a new study.
Scientists have discovered that tirzepatide, a medication used to treat obesity and type 2 diabetes, may not only reduce appetite but also change how the body burns energy.
This finding could help explain why the drug has been so effective and may lead to better treatments for obesity in the future.
Tirzepatide, sold under the brand name Mounjaro, has gained attention because it can lead to significant weight loss and improved blood sugar control. Doctors often prescribe it to people with obesity or those who are overweight and have related health problems.
It is also used for people whose type 2 diabetes is not well controlled. Many patients taking the drug eat less because they feel full sooner, which leads to weight loss. However, scientists have suspected that something more might be happening inside the body.
The new study, conducted by researchers from the University of Barcelona and several related institutes, looked at how tirzepatide affects different types of body fat. The research was performed in mice because detailed testing of internal fat tissue is difficult in humans.
The scientists fed mice a high-fat diet to make them obese, then treated some of them with tirzepatide while keeping a separate group untreated but eating the same amount of food. This allowed researchers to see whether the drug itself had effects beyond simply reducing appetite.
The results showed that tirzepatide activates brown fat, a special type of body fat that burns calories to produce heat. Unlike white fat, which stores energy and builds up around the waist and organs, brown fat uses energy and helps control body temperature.
Brown fat is especially important because it can burn both sugar and fat, improving metabolism and reducing harmful substances in the blood.
When brown fat becomes more active, the body burns more calories even at rest. The study found that mice treated with tirzepatide had higher activity in their brown fat, which increased their ability to use energy. The researchers also observed the release of helpful molecules from brown fat that support healthy metabolism.
This discovery suggests that tirzepatide may help the body lose weight in two ways at the same time. It reduces food intake by making people feel full, and it increases energy use by activating brown fat. This dual effect could explain why the drug leads to greater weight loss than many older treatments.
Scientists have long hoped to find safe ways to activate brown fat because doing so could treat obesity and related diseases. Previous attempts to stimulate brown fat with drugs often caused side effects, especially problems affecting the heart.
The new study suggests that tirzepatide may activate brown fat without those harmful effects, and it may even improve heart health.
Researchers believe that understanding exactly how tirzepatide works could lead to more personalized treatments. In the future, doctors might choose medications based not only on a patient’s weight but also on how their metabolism functions. This could help people who struggle to lose weight despite eating less.
However, the researchers warn that the findings come from animal studies, and human bodies may respond differently. More clinical trials will be needed to confirm whether the same effects occur in people. Even so, the study provides valuable clues about how the drug works and opens new paths for developing better therapies.
In reviewing the findings, the research highlights the growing understanding that obesity is not simply a matter of eating too much. It involves complex biological systems that control hunger, energy use, and fat storage.
Treatments that target several of these systems at once are likely to be more effective. While tirzepatide is not a cure for obesity, it represents a major step toward therapies that address the condition from multiple angles.
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The study is published in Biomedicine & Pharmacotherapy.
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