A new study suggests that combining two medicines may help people lose a large amount of weight while protecting their muscles at the same time.
The research looked at a treatment that uses semaglutide, a well-known weight‑loss drug, together with another drug called bimagrumab. Scientists found that the combination produced greater weight loss than either drug alone while keeping most of the body’s lean tissue, including muscle.
The study was published in 2026 in the journal Nature Medicine. It was led by Dr. Steven Heymsfield at the Pennington Biomedical Research Center in the United States. The research was part of a clinical trial called the BELIEVE study. Clinical trials like this are designed to test whether new medical treatments are safe and effective for people.
Obesity has become one of the most serious health challenges around the world. According to health experts, hundreds of millions of adults are living with obesity.
The condition increases the risk of many health problems, including heart disease, type 2 diabetes, high blood pressure, and certain cancers. For many years, doctors have searched for better treatments that help people lose weight safely and maintain their health.
In recent years, drugs known as GLP‑1 receptor agonists have become very popular for weight loss. Semaglutide is one of the most widely used medicines in this group.
These drugs work by copying the action of a natural hormone in the body called GLP‑1. The hormone helps control blood sugar and also affects the brain’s appetite signals. As a result, people feel full sooner and eat less food.
These medicines have been very effective. Many people taking semaglutide can lose a significant amount of weight. However, doctors have noticed an important issue.
When people lose weight, not all of the weight loss comes from fat. Some of the lost weight comes from lean body mass, which includes muscle, organs, and connective tissue. Research suggests that as much as 40 percent of weight lost during treatment with GLP‑1 drugs may come from lean mass.
Losing too much muscle can create problems. Muscle helps the body move, stay strong, and maintain a healthy metabolism. Lower muscle mass can affect physical ability and may also influence how the body handles sugar and energy. Because of this, many researchers are trying to find treatments that reduce body fat while protecting muscle.
Bimagrumab is a different type of medicine that may help solve this problem. It is an antibody that blocks signals from proteins called activins. These signals normally limit muscle growth.
When the signals are blocked, muscle tissue may increase while body fat decreases. Earlier studies suggested that bimagrumab could reduce fat and increase muscle mass, which made scientists interested in combining it with weight‑loss medicines like semaglutide.
To test the idea, researchers carried out a randomized clinical trial. This means participants were placed into different groups by chance so that the results would be fair and unbiased.
The study was also double‑blind and placebo‑controlled. In this type of trial, neither the participants nor the researchers know who receives the real medicine or a placebo until the study is finished.
Participants in the study were divided into several groups. Some received only bimagrumab, some received only semaglutide, and others received both medicines together.
The drugs were given at two different dose levels, creating nine treatment groups in total. Bimagrumab was given once every 12 weeks, while semaglutide was taken once a week. The trial lasted for 72 weeks, which is about a year and four months.
The results were striking. People who received only bimagrumab lost about 10.8 percent of their body weight on average. Interestingly, this weight loss came entirely from fat, and their lean body mass actually increased by about 2.5 percent.
Participants who received only semaglutide lost about 15.7 percent of their body weight. Most of this loss came from fat, but some lean mass was also lost, which is consistent with what doctors have seen in previous studies.
The most dramatic results were seen in people who received the combination of both drugs. On average, they lost about 22.1 percent of their body weight over the 72‑week study period. Even more important, about 92.8 percent of the weight loss came from body fat. Lean mass was largely preserved.
Dr. Heymsfield explained that obesity treatment has traditionally focused on the number shown on the scale.
However, the new findings suggest that doctors may need to pay more attention to body composition, which looks at how much of the body is made up of fat versus muscle. Treatments that reduce fat while keeping muscle could provide greater health benefits for patients.
The study also found improvements in other health markers. Levels of high‑sensitivity C‑reactive protein, which is linked to inflammation and heart disease risk, dropped by as much as 83 percent in some participants.
The treatment also increased adiponectin, a hormone that helps improve the body’s response to insulin and supports healthy fat metabolism.
Another encouraging result appeared in people who had signs of prediabetes at the beginning of the study. In some of the groups receiving the two‑drug combination, every participant with prediabetes returned to normal blood sugar levels by the end of the trial.
The treatment was generally well tolerated by participants. Most side effects were similar to those already known for the individual drugs. However, researchers reported some mild to moderate problems in groups receiving bimagrumab, including acne and muscle spasms.
Although the results are promising, the researchers say more studies are needed. Larger clinical trials will help confirm the benefits and better understand possible side effects. Scientists also want to learn which patients may benefit most from the treatment and what the best doses might be.
Overall, the study provides an important step forward in obesity treatment. It suggests that future therapies may focus not only on helping people lose weight, but also on improving body composition by reducing fat while protecting muscle.
If these findings are confirmed in further research, the combination of semaglutide and bimagrumab could become a new approach to treating obesity and related metabolic diseases.
If you care about weight loss, please read studies that hop extract could reduce belly fat in overweight people, and early time-restricted eating could help lose weight .
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