People who stop using the weight-loss injection Mounjaro are likely to regain weight and lose many of the health improvements they experienced while on the drug, according to new research.
Mounjaro, which contains tirzepatide, has been shown to help people lose around 20% of their body weight after long-term use. However, researchers analysing data from the Surmount-4 clinical trial found that stopping the medication not only led to weight regain, but also reversed gains in blood pressure, cholesterol and blood sugar control.
In the study, all participants received tirzepatide along with diet and exercise support for 36 weeks. They were then split into two groups: one continued the drug and the other was switched to a placebo for a further year, without knowing which they were receiving.
Among 308 participants who had lost at least 10% of their body weight initially, 82% of those who stopped the drug regained at least a quarter of their lost weight within a year. Greater weight regain was linked to greater worsening of waist size, “bad” cholesterol, blood pressure and blood glucose. Those who regained 75% or more of their lost weight saw their health measures return to pre-trial levels.
Professor Naveed Sattar of the University of Glasgow said the findings were expected, as excess weight is a major driver of poor cardiometabolic health. He noted that stopping treatment could also remove protective effects against heart failure and other serious conditions.
Experts added that weight-loss injections do not always lead to lasting healthy habits. Professor Jane Ogden of the University of Surrey said some people become less motivated to eat well or exercise while on the drugs, making weight regain more likely once treatment stops.
Separate research has suggested that women who stop these medications shortly before or during pregnancy may face higher risks of weight gain, preterm birth and pregnancy-related complications, though experts stress that more research is needed to confirm cause and effect.
Researchers concluded that long-term strategies, including sustained lifestyle changes and, when appropriate, ongoing medication, are important to maintain both weight loss and overall health benefits.
