A large international study has found that while popular obesity medications continue to deliver significant weight-loss results, most do not produce meaningful improvements in overall quality of life after one year of treatment.

The research, published in The BMJ, reviewed 262 clinical trials involving nearly 100,000 participants and evaluated 19 different weight-loss medications. The findings suggest that although many of the drugs effectively reduce body weight, their broader health benefits may be more limited than previously expected.

Researchers reported that greater weight loss was consistently linked with higher rates of side effects and a greater likelihood that patients would discontinue treatment.

The study concluded that most medications did not produce clinically significant improvements in health-related quality of life when compared with lifestyle changes alone. Participants across the clinical trials completed standardized questionnaires measuring physical and mental well-being, and researchers found only modest differences between those taking medication and those relying on diet and exercise programs.

Among the treatments evaluated, tirzepatide, the active ingredient in Mounjaro and Zepbound, produced the greatest weight reduction. CagriSema, an experimental treatment that has not yet been approved for clinical use, also ranked among the most effective therapies for reducing body weight.

Semaglutide, the active ingredient used in Ozempic and Wegovy, showed the strongest evidence for lowering the risk of death and major cardiovascular events, making it one of the best-supported treatments for patients with obesity and related health conditions.

Despite these benefits, researchers found that both tirzepatide and semaglutide were associated with a reduction in lean body mass, which includes muscle, bone and other non-fat tissues. Loss of lean mass has been linked to a higher risk of falls, fractures and other health complications, particularly among older adults.

The authors cautioned that many of the clinical trials followed participants for relatively short periods, making it difficult to fully assess the long-term safety and effectiveness of newer medications. They called for additional research to better understand how these drugs affect patients over several years.

Independent experts also urged caution when interpreting the findings on quality of life. Marie Spreckley of the University of Cambridge said quality of life is influenced by many personal and social factors that standardized questionnaires may not fully capture.

The researchers also emphasized that obesity is increasingly recognized as a chronic medical condition requiring a broader approach to treatment. They argued that focusing only on body weight may overlook other important measures of success, including physical function, mental health and overall well-being.

José M. Ordovás of Tufts University, who was not involved in the research, said the findings reinforce the idea that weight loss alone does not guarantee improvements in every aspect of health.

He said obesity treatment should be evaluated using a wider range of outcomes, including long-term health, daily functioning and quality of life, rather than relying solely on changes shown by the scale.