A new analysis finds that semaglutide protects the heart in ways that weight loss alone cannot explain. Traditional risk factors account for no more than half of the reduction in cardiovascular disease seen in the international SELECT trial.
Semaglutide appears to protect patients from serious cardiovascular events through more than weight loss. A new analysis of the international SELECT trial found that changes in body weight and waist size cannot fully explain the drop in heart attacks, strokes and vascular deaths. The missing mechanism is now one of the main scientific questions around Ozempic and Wegovy.
The finding is unusually clear. Conventional explanations cover no more than half of the benefit seen in the trial.
SELECT included 17,604 adults with overweight or obesity, established cardiovascular disease and no diabetes. Participants received weekly semaglutide 2.4 milligrams or placebo and were followed for about four years.
Published in the European Heart Journal, the analysis looked at more than 17,000 participants over four years. They received either a weekly 2.4 milligram dose of semaglutide or a placebo. Researchers tracked changes in body weight, blood pressure, cholesterol, inflammation markers and kidney function. They then tested how much those changes could explain the cardiovascular results. The analysis used the SELECT population, not a separate trial.
Every major measure improved in the treated group. Even so, the measures did not explain the full drop in risk, whether researchers looked at them together or separately. Helen Colhoun of the Universidad de Edinburgo said the available analysis could not link semaglutide's cardiovascular effect to known risk factors "with total certainty." The drug's clinical effect therefore reaches beyond the mechanisms most often used to explain obesity related heart disease.
The original SELECT result was a 20% reduction in major adverse cardiovascular events: 6.5% of participants in the semaglutide group experienced such an event compared with 8.0% in the placebo group, corresponding to a hazard ratio of 0.80. The new analysis examines why that benefit cannot be fully attributed to conventional risk-factor changes.
That changes how doctors may read the treatment's results. Weight loss remains an important effect, but the data do not support treating it as the only reason patients have fewer major cardiovascular events. Expert commentary collected by the Science Media Centre also describes a substantial part of the benefit as unexplained by standard surrogate measures.
Researchers are considering several possible explanations. Semaglutide may lower inflammation in tissues. It may improve the endothelium, the lining of blood vessels. It may also directly protect the heart muscle. The analysis did not establish any of these explanations. Together, they show why the cardiovascular result cannot be reduced to a smaller waistline.
Andreu Palou of the Universitat de Islas Baleares also says weight loss is not enough to explain the protection seen in the trial. Cristóbal Morales leads the Unidad de Salud Metabólica, Diabetes y Obesidad at Hospital Vithas Sevilla and coordinates SELECT in Spain. He said the combined improvements in weight, inflammation, glucose control and blood pressure account for only part of the effect.
Morales sees the result as evidence that semaglutide is more than a slimming treatment. The drug class has reduced major cardiovascular events by about 20%, according to material presented with the study. In outside discussions of the analysis, roughly 69% of the observed effect is described as needing further investigation. That figure is an interpretation of the mediation analysis, not proof of one additional biological mechanism. The evidence points to a wider clinical role focused on vascular protection, not appearance alone.
The question matters to patients and families making long term treatment decisions. It also comes alongside other pressures affecting household choices in Spain, including those covered in the earlier housing analysis. The medical evidence here, though, concerns cardiovascular outcomes rather than household finances.
The regulatory stakes have also grown. After the SELECT findings, the U.S. Food and Drug Administration expanded Wegovy's indication to reduce the risk of major cardiovascular events in adults with established cardiovascular disease and overweight or obesity. The decision rests on demonstrated outcome data. It does not mean that every biological pathway has been identified.
An editorial accompanying the study was written by cardiac surgeon Subodh Verma and colleagues at the Universidad de Toronto. They argue that incomplete knowledge of the biological pathway should not prevent therapeutic use. That view is reasonable. Medicine often relies on demonstrated outcomes before every molecular detail is known. The missing mechanism still matters, though. Finding it could help doctors refine treatment and identify which patients receive the greatest protection. The SELECT data show that semaglutide's cardiovascular benefit is real. The biology behind it remains unfinished science.
