A new real-world study presented at the European Congress on Obesity 2026 suggests that popular obesity medications such as semaglutide and tirzepatide may help patients lose mostly fat while preserving much of their muscle mass.
Researchers from the Medical University of Vienna and Metabolism Center N°12 Antonigasse evaluated 486 adults with obesity who were treated with GLP-1 receptor agonists or dual GIP/GLP-1 therapies between 2022 and 2025. The analysis found that patients lost an average of nearly 10% of their body weight after around 14 months of treatment.
According to the findings, about 80–85% of the weight reduction came from fat mass rather than muscle. Patients lost an average of 9 kilograms of fat, while skeletal muscle mass declined by only around 1.2 kilograms. More than 70% of participants maintained or even improved their relative muscle mass during treatment.
The study focused on widely used obesity medications including semaglutide, liraglutide, and tirzepatide. Researchers used Bioelectrical Impedance Analysis (BIA), a non-invasive technique that estimates body composition by measuring fat, lean muscle, and body water levels.
Scientists say the findings are important because concerns have grown around possible muscle loss linked to rapid weight reduction with GLP-1 drugs. Maintaining muscle mass is considered essential for long-term metabolic health, physical strength, and overall quality of life.
The researchers noted that when changes in fat mass were considered, muscle mass remained relatively stable over time. This indicates that the medications may support healthier body composition changes rather than causing harmful muscle wasting.
However, the authors also cautioned that the study had limitations. It was a retrospective analysis without a placebo group, and most participants were female. They emphasized that larger long-term clinical trials are still needed to better understand the lasting effects of these therapies on muscle health.
GLP-1-based obesity treatments have gained significant attention worldwide in recent years due to their strong impact on weight reduction and metabolic health. The latest findings could help reassure clinicians and patients concerned about muscle preservation during obesity treatment.
