People who stop weight loss jabs regain the weight they lost in under two years, a study has found.
Researchers said the pace of weight regain after stopping the drugs was almost four times faster than after behavioural programmes, such as structured diet or exercise plans, regardless of how much weight people lost during treatment.
Dr Sam West, of the Nuffield Department of Primary Care Health Sciences at the University of Oxford, said: “These medicines are transforming obesity treatment and can achieve important weight loss.
“However, our research shows that people tend to regain weight rapidly after stopping, faster than we see with behavioural programmes.
“This isn’t a failing of the medicines – it reflects the nature of obesity as a chronic, relapsing condition.
“It sounds a cautionary note for short-term use without a more comprehensive approach to long-term weight management, and highlights the importance of primary prevention.”
The study, led by academics at the University of Oxford and published in the BMJ, reviewed 37 existing studies involving 9,341 participants.
The average duration of treatment was 39 weeks and the average follow-up period was 32 weeks.
On average, weight was regained at a rate of 0.4kg a month after people stopped taking the medication, with participants returning to their original weight within an average of 1.7 years.
People taking any weight loss medication lost an average of 8.3kg during treatment but regained 4.8kg within the first year.
The study also found the benefits on cardio-metabolic health markers, such as blood pressure and cholesterol, returned to their original levels within 1.4 years of stopping treatment.
The medicines, known as GLP-1 agonists, were originally developed to treat diabetes.
They work by mimicking the glucagon-like peptide 1 hormone, which helps people feel full.
Wegovy can be prescribed on the NHS for up to two years, while there is no prescription time limit for Mounjaro.
Dr Faye Riley, research communications lead at Diabetes UK, said: “Weight loss drugs can be effective tools for managing weight and type 2 diabetes risk – but this research reinforces that they are not a quick fix.
“They need to be prescribed appropriately, with tailored wraparound support alongside them, to ensure people can fully benefit and maintain weight loss for as long as possible when they stop taking the medication.”
Katharine Jenner, executive director of the Obesity Health Alliance, said regaining weight after stopping treatment was not a failure of individuals but rather “reflects the reality of living in a food environment that continually pushes people towards unhealthy options.”
She added: “These drugs can create a window of opportunity to improve the food environment at scale and pace – from junk food marketing to the affordability and availability of healthier food – otherwise many people will struggle to sustain the health benefits of weight loss drugs over the long term.”
An NHS spokesperson said: “While these new treatments are an important new tool for supporting weight loss, they’re not a magic fix and must be paired with behavioural and lifestyle wraparound support including advice on healthier diets and physical activity to keep the weight off in the long term.
“The NHS continues to implement innovative ways to support people to lose weight safely and sustainably as well as offering a range of weight management services, including the NHS digital weight management programme, which will be expanded to 125,000 more people per year as part of the 10-year health plan.”
