People who stop using the weight-loss drug Mounjaro tend to regain lost weight and lose many of the accompanying health benefits, according to new research.
Mounjaro, which contains tirzepatide, has helped users lose around 20% of their body weight in clinical studies. But previous research has shown that much of this weight often returns once treatment stops.
A new analysis from the Surmount-4 clinical trial shows that improvements in blood pressure, blood glucose and levels of “bad” cholesterol also reverse after people discontinue the injections. Naveed Sattar, professor of cardiometabolic medicine at the University of Glasgow, said this outcome is expected, since regained weight usually brings back cardiometabolic risks.
The Surmount-4 trial followed participants with obesity or weight-related health issues who took tirzepatide for 36 weeks before half switched to a placebo for a year. Among 308 people who had lost at least 10% of their body weight, 82% regained at least a quarter of that lost weight within 12 months of stopping the drug.
Greater weight regain was linked to a stronger reversal of health improvements. Those who regained 75% or more of their lost weight saw cardiometabolic markers return to their original baseline levels. Participants who regained up to half still showed some lasting improvements.
Researchers said the findings highlight the importance of long-term weight management and continued treatment for maintaining health benefits. Experts also noted that weight-loss medication does not always lead to healthier habits, and many people return to old behaviours once they stop the injections.
Additional studies have suggested that stopping drugs like tirzepatide or semaglutide before or during early pregnancy may be linked to higher risks of gestational complications, though experts caution that more research is needed to confirm cause and effect.
