The trial involved more than 17,600 people from across 41 countries.
Weight loss jabs can reduce the risk of a heart attack or stroke in obese people with cardiovascular disease by a fifth, researchers claim.
Pharmaceutical company Novo Nordisk conducted a five-year study of semaglutide, which is sold as Wegovy.
As part of its Select trial, the company recruited 17,604 adults over the age of 45 from across 41 countries.
Each patient had a body mass index (BMI) of 27 or over and established cardiovascular disease, with no history of diabetes.
Researchers found that the risk of heart attack or stroke in patients given a 2.4mg once-weekly dose of Wegovy, alongside standard care for the prevention of heart attacks or stroke, reduced by 20% compared with those given a placebo drug.
Martin Holst Lange, executive vice president for development at Novo Nordisk, said: “People living with obesity have an increased risk of cardiovascular disease, but to date there are no approved weight management medications proven to deliver effective weight management while also reducing the risk of heart attack, stroke or cardiovascular death.
“Therefore, we are very excited about the results from Select showing that semaglutide 2.4mg reduces the risk of cardiovascular events.
“Select is a landmark trial and has demonstrated that semaglutide 2.4mg has the potential to change how obesity is regarded and treated.”
Novo Nordisk said it expects to file for regulatory approvals of a label indication expansion for Wegovy in the US and the EU in 2023.
Professor Stephen O’Rahilly, director of the MRC Metabolic Diseases Unit at the Institute of Metabolic Science, University of Cambridge, said the results “have been long awaited and do not disappoint”.
He added: “Simply put, a drug which acts to reduce body weight by targeting appetite, if taken long term by people who are overweight or obese, significantly reduces their risk of serious cardiovascular events, such as heart attack.
“The obvious conclusion of these findings is that we should view obesity as a medical condition, like high blood pressure, where effective and safe drug therapy can contribute to reducing serious adverse health outcomes.”
The results come after experts suggested that obese people on weight loss jabs should be prepared to take them for life.
Earlier this year, the National Institute for Health and Care Excellence (Nice) recommended the use of Wegovy for adults with a BMI of at least 35 and one weight-related health condition such as diabetes or high blood pressure.
The regulator said it should not be taken for more than two years, but studies show that people who stop weight loss jabs, such as Wegovy, can regain much of the weight they have lost.
A team of obesity experts argue Nice guidance is largely based on the cost of the drugs and that people who take them should be prepared to take them long term for treating their disease.
John Wilding, a professor of medicine who leads clinical research into obesity, diabetes and endocrinology at the University of Liverpool, said: “We do have to think about these medicines as long-term medications despite the fact that, for Nice at the moment, it’s only two years of treatment.
“We do know that obesity is a chronic disease and we would never think of just giving somebody a diabetes drug or blood pressure drug for two years and then stopping it because, of course, at that point the disease will recur.
“We know that happens with obesity. So, I do think we have to think about this as long-term treatment and that’s something that is yet to be addressed from a policy perspective.”