Over the past few years, weight-loss injections like Mounjaro (tirzepatide) and Wegovy (semaglutide) have been shown to be effective for weight loss.
Living with excess weight increases the risk of cardiovascular disease, so taking these GLP-1 agonist medicines to lose weight can reduce the risk of having a heart attack or stroke.
And research suggests these weight-loss drugs, initially developed for people with diabetes, have added benefits for the heart as they improve other risk factors for cardiovascular disease. These include:
• high blood pressure (hypertension)
• high cholesterol
• high blood sugar
• large waist
However, studies show that when people stop taking GLP-1 agonist weight-loss injections they are at risk of regaining a significant amount of weight.
And now new research, reported in the UK media, suggests that the other health gains are reversed too.
The 2025 study, published in November’s JAMA Internal Medicine, found that if people put weight back on after stopping Mounjaro, they also lost these benefits to their cardiovascular health.
These findings suggest that people may need to continue taking weight-loss injections to maintain any weight loss and other health benefits they’ve gained from the medicine.
What happens when you stop taking Mounjaro?
Like other weight-loss injections, Mounjaro mimics hormones in your body that slow down your digestion, lower your appetite and make you feel fuller after eating. This helps you eat less and lose weight.
When you stop taking the drug, your appetite returns to normal, and some people find they start eating more and regain the weight they lost while taking the drug.
Unlike other weight-loss injections, there’s currently no time limit on how long you can take Mounjaro if you’re part of the limited number of people who fit the criteria to be prescribed the drug on the NHS.
But there are other reasons people stop taking Mounjaro, such as side effects, or other medical reasons, and cost if they pay for the medicine privately.
What did the research find about stopping Mounjaro?
The study was an analysis of a previous trial called SURMOUNT-4, which included 670 people from the United States, Argentina, Brazil and Taiwan, who did not have diabetes and were living with either obesity or excess weight and at least 1 weight-related health issue.
They were given weekly injections of Mounjaro for about 9 months (36 weeks). Then, half continued taking Mounjaro, while the other half were given a dummy injection with no medicine for another year (52 weeks).
To help with lifestyle changes, all participants received advice from a dietitian on how to manage their weight by eating a lower energy (calories) diet and doing more physical activity for the entire 88 weeks of the study.
The researchers behind the new study analysed data from 308 participants who’d lost a clinically significant amount of weight—at least 10 per cent of their original bodyweight—after 9 months on Mounjaro, before being given the dummy injection for a year.
They found, on average, people experienced significant decreases in their waist size, blood pressure, cholesterol and blood sugar levels when they were taking Mounjaro.
However, a year after stopping Mounjaro, most of the participants taking the dummy medicine had regained weight, despite the support they’d received to adopt a healthier lifestyle.
Findings showed: • Around 8 out of 10 participants (82 per cent) who stopped taking Mounjaro regained at least a quarter of the weight they’d lost. • Around 2 in 10 participants (24 per cent) regained 3 quarters to all of the weight they’d lost. • Nearly 1 in 10 (9 per cent) regained all of the weight they’d lost.
The researchers looked to see if those that regained a quarter or more of their initial weight also experienced changes to their waist size, blood pressure, cholesterol and blood sugar levels.
They found those who gained the most weight after stopping Mounjaro also experienced the greatest reversal in reductions they’d seen in waist size, blood pressure, cholesterol and blood sugar levels.
