Stopping popular weight-loss drugs may quickly raise the risk of heart attack and stroke, a major new study has found.

Researchers at Washington University School of Medicine in St. Louis tracked more than 333,000 US veterans with type 2 diabetes for three years. The findings were published in BMJ Medicine.

People who stopped GLP-1 drugs for as little as six months faced a higher risk of major heart events than those who stayed on them. After two years off treatment, the risk of heart attack, stroke and death was 22% higher.

Continuous users had an 18% lower risk of major heart events than patients on older sulfonylurea medicines. That meant about four fewer heart events per 100 people over three years.

Restarting the drugs restored some protection, but not all of it, the study found.

“There is enormous exuberance about starting GLP-1 drugs, but not nearly enough attention to what happens when people stop,” said senior author Ziyad Al-Aly. He noted many quit over cost, side effects or shortages.