People who stop taking weight loss injections regain all the weight they initially lost within less than two years—at a significantly faster rate than those following any other weight loss approach—according to a landmark new study.
How GLP-1 Weight Loss Drugs Work
Weight loss medications, known as GLP-1 agonists, were originally developed to treat diabetes. These drugs mimic the glucagon-like peptide-1 hormone, which helps regulate appetite by increasing feelings of fullness and reducing food intake.
Oxford-Led Study Analyses Long-Term Outcomes
Researchers from the University of Oxford, in a study published in The BMJ, reviewed 37 existing studies involving 9,341 participants who used weight loss medications. On average, participants remained on treatment for 39 weeks, followed by a 32-week follow-up period after stopping the drugs.
Weight Returns Within Two Years of Stopping Treatment
As reported by The Guardian, the analysis found that participants regained weight at an average rate of 0.4 kg per month after discontinuing medication. As a result, most individuals returned to their original body weight within approximately 1.7 years, regardless of the type of weight loss drug used.
During treatment, participants lost an average of 8.3 kg, but regained 4.8 kg within the first year after stopping medication.
Faster Regain Compared With Behavioural Programmes
Importantly, the study revealed that weight regain occurred almost four times faster after stopping weight loss drugs than after ending behavioural weight loss programmes. These programmes typically involve structured dietary changes or physical activity plans, and the difference remained consistent regardless of how much weight participants initially lost.
Experts Stress Obesity Is a Chronic Condition
Dr Sam West, from the Nuffield Department of Primary Care Health Sciences at the University of Oxford, emphasised that the rapid weight regain does not reflect a failure of the medication.
“These medicines are transforming obesity treatment and can achieve important weight loss,” he said. “However, people tend to regain weight rapidly after stopping—faster than we see with behavioural programmes.”
He added that obesity is a chronic, relapsing condition, warning against short-term use of weight loss drugs without a long-term management strategy. The findings, he said, highlight the importance of prevention and sustained lifestyle support.
Metabolic Benefits Also Reverse After Stopping
While previous research has shown that weight loss drugs can improve cardiovascular and metabolic health, the study found that these benefits also diminish over time. Improvements in blood pressure and cholesterol levels returned to pre-treatment levels within an average of 1.4 years after stopping medication.
Notably, this is the first study to quantify both the rate of weight regain and the timeline for metabolic reversal following discontinuation of weight loss drugs.
Prescribing Practices and Expert Caution
In the UK, Wegovy can be prescribed on the NHS for up to two years, while Mounjaro currently has no prescription time limit.
Dr Faye Riley, Research Communications Lead at Diabetes UK, said the findings reinforce that weight loss drugs are not a quick fix.
“These medications can be effective tools for managing weight and reducing the risk of type 2 diabetes,” she said. “However, they must be prescribed appropriately and supported by tailored, long-term care to help people maintain weight loss after stopping treatment.”
Broader Food Environment Plays a Role
Katharine Jenner, Executive Director of the Obesity Health Alliance, stressed that weight regain should not be viewed as an individual failure.
“It reflects the reality of living in a food environment that continually pushes people towards unhealthy options,” she said. She added that weight loss drugs could provide a window of opportunity to improve food policies—ranging from junk food marketing restrictions to better access to affordable, healthy food.
NHS Emphasises Lifestyle Support
An NHS spokesperson echoed these views, stating that while weight loss drugs represent an important new tool, they must be paired with behavioural and lifestyle support.
“They are not a magic fix,” the spokesperson said. “Long-term success depends on healthier diets, physical activity, and access to structured weight management services.”
The NHS continues to expand its digital weight management programme, which will support an additional 125,000 people per year as part of its 10-year health plan.