Obesity has become one of the biggest health challenges in the world.
Millions of people struggle with excess weight, and many also face serious health problems linked to obesity, including diabetes, heart disease, high blood pressure, sleep apnea, joint pain, and fatty liver disease.
For many years, doctors mainly recommended diet changes, exercise, and traditional weight-loss medicines. However, losing a large amount of weight and keeping it off has often been very difficult for patients.
In recent years, a new group of medicines called GLP-1 drugs has changed the treatment of obesity. These medicines include semaglutide, liraglutide, and tirzepatide.
They work by helping people feel full for longer, reducing hunger, slowing stomach emptying, and helping control blood sugar levels. Many people using these medicines have lost significant amounts of weight, and some studies have shown improvements in heart health and diabetes risk as well.
Despite these benefits, many doctors and patients have worried about one important issue. When people lose weight quickly, they sometimes lose muscle along with body fat.
Muscle is very important for strength, movement, metabolism, balance, and healthy aging. Losing too much muscle can increase weakness and lower quality of life, especially in older adults.
Now, new research presented at the European Congress on Obesity (ECO2026) in Istanbul, Turkey, offers encouraging news. The study found that most of the weight lost during GLP-1 treatment comes from fat rather than muscle. In many patients, muscle mass was largely preserved.
The research was carried out by Emilia Ida Frohner, Dr. Alexander Jürets, and Dr. Bianca Karla-Itariu from the Metabolism Center N°12 Antonigasse and the Medical University of Vienna in Austria.
The scientists studied 486 adults with obesity who were treated at a private obesity clinic in Vienna between 2022 and 2025.
Most of the participants were women, with women making up 82% of the group and men making up 18%. The average age was nearly 50 years old, and the average body mass index, or BMI, was around 37.7, which falls within the obesity range.
The patients were treated with different obesity medicines. About 82% received semaglutide, while smaller groups used liraglutide or tirzepatide. Along with medication, all patients were encouraged to follow physical activity recommendations based on current medical guidelines.
To measure body changes, researchers used a method called bioelectrical impedance analysis, or BIA. This method is simple, fast, and does not involve surgery or needles.
It works by sending a very small electrical current through the body to estimate how much of the body is made up of fat, muscle, and water. Muscle carries electricity better than fat, so the machine can estimate body composition.
The researchers believed body composition was more important than body weight alone. Losing fat while keeping muscle is considered a healthier outcome than losing both equally.
After an average treatment period of about 14 months, the patients lost nearly 10% of their body weight on average. Fat mass dropped by around 9 kilograms, which was about an 18% reduction in body fat. In contrast, muscle mass decreased by only about 1.2 kilograms, or around 5%.
Even more encouraging, more than 70% of patients either maintained or increased their relative muscle mass during treatment. This means that while they lost weight overall, the percentage of muscle in their bodies stayed stable or improved.
The researchers also used computer models to better understand the results. They adjusted for factors such as age, sex, BMI, treatment time, and fat loss. Their analysis showed that the reduction in muscle was mostly proportional to the reduction in body size and fat mass, rather than a dangerous loss of muscle tissue.
The scientists explained that the results suggest GLP-1 drugs mainly help reduce fat while preserving muscle relatively well. This is important because one criticism of rapid weight loss has been the fear of muscle wasting.
The study also highlights how obesity treatment is changing. In the past, doctors often focused only on body weight. Today, experts increasingly believe that body composition matters much more.
A person who loses fat but keeps healthy muscle may have better long-term health outcomes than someone who simply loses weight without considering body composition.
Still, the researchers noted several limitations. This was a retrospective study, meaning the scientists looked back at existing medical records instead of running a controlled clinical trial.
There was no placebo group for comparison, and most participants were women, which means the findings may not fully apply to men or all patient groups.
The researchers also said longer and larger studies are still needed to understand the long-term effects of GLP-1 drugs on muscle and body composition over many years.
Overall, the findings are reassuring for patients worried about muscle loss during weight-loss treatment. The results suggest that GLP-1 medicines may help people lose mostly fat while preserving strength-related muscle tissue.
The research was presented at the European Congress on Obesity (ECO2026).
In reviewing the findings, the study appears important because it addresses one of the biggest concerns surrounding modern obesity drugs. The results suggest these medicines may support healthier body composition changes rather than harmful muscle wasting.
However, because the study was observational and heavily focused on female patients, stronger clinical trials are still necessary before drawing firm conclusions for all populations.
Even so, the findings provide encouraging evidence that GLP-1 drugs may offer safer long-term weight reduction than many experts previously feared.
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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