The findings come as real-world data shows around half of people discontinue GLP-1 receptor agonist treatment within 12 months, and just months after NICE published quality standards recommending post-treatment support for at least one year.
Across 37 studies including 9,341 adults, weight increased by an average of 0.4 kg (0.9 pounds) per month after weight management drugs were stopped. Researchers estimate that, at this rate, people would return to their starting weight within 1.5 to 2 years. For newer medicines such as semaglutide and tirzepatide, regain averaged 0.8 kg (~1.8 pounds) per month, with projections indicating return to baseline by approximately 1.5 years – though information on weight change beyond 12 months after these drugs remains limited.
These findings suggest that treating obesity requires long-term commitment, not just from patients but from healthcare systems too.
Crucially, weight regain after stopping drugs was faster than after ending behavioural weight loss programmes such as diet and exercise support by approximately 0.3 kg (0.7 pounds) per month – independent of how much weight was initially lost. While behavioural support alongside medication was associated with greater weight loss, it did not slow the rate of regain afterwards.
Cardiometabolic markers including HbA1c, fasting glucose, blood pressure, cholesterol and triglycerides improved during treatment but are estimated to return to baseline levels within approximately 1.4 years after medicines stopped.
"These medicines are transforming obesity treatment and can achieve important weight loss. However, our analysis shows that people tend to regain weight rapidly after stopping – faster than we see with behavioural programmes," says lead author Dr Sam West, postdoctoral researcher at the Nuffield Department of Primary Care Health Sciences, University of Oxford. "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 weight management."
The research
The Oxford team systematically reviewed 37 studies tracking more than 9,000 adults who stopped taking weight management medicines after being on them for an average of 39 weeks of treatment. Participants were followed for an average of 32 weeks after stopping. The analysis included medicines from older drugs like orlistat to newer GLP-1 receptor agonists like semaglutide and tirzepatide. The team used three different analytical approaches, all of which produced consistent results.
Comparison with behavioural programmes
When comparing weight management medicines to behavioural programmes using data from a previous systematic review, the researchers found regain was faster after medicines by approximately 0.3 kg per month – regardless of initial weight lost.
"This faster regain could be because people using drugs don't need to consciously practise changing their diet to lose weight, so when they stop taking the medication they might not have developed the practical strategies that could help them keep it off," says senior author Associate Professor Dimitrios Koutoukidis. "Our findings also have implications for cost-effectiveness. NICE's initial estimates assumed weight would return to baseline over two to three years – our data suggests this happens in around 18 months. This doesn't mean these drugs aren't valuable, but it does support the NHS approach of prioritising people with severe and complex obesity who are most likely to benefit."
Implications for patients and prescribers
An estimated nine in ten people currently using weight-loss medicines in the UK are purchasing them privately, often without the comprehensive clinical oversight and behavioural support that accompanies NHS prescribing.
Professor Susan Jebb, joint senior author, adds: "Obesity is a chronic, relapsing condition, not a short-term problem with a quick fix. When people lose weight through changes to their diet and activity, they're practising the skills that help maintain that loss. It may be that with medication, the weight comes off without necessarily developing those skills. These findings underscore the need for a more holistic and long-term approach to weight management, and increased emphasis on the importance of primary prevention of weight gain."
"For practitioners prescribing, patients receiving, and people choosing to purchase these medications privately, it's important to understand the risks of rapid weight regain if treatment ceases – and the value of wraparound behavioural support."
Study limitations
The researchers note several limitations. The number of studies examining newer medicines like semaglutide and tirzepatide remains relatively small, and follow-up durations after stopping medicines were generally short, meaning some estimates are modelled projections beyond observed follow-up. Most studies were conducted in controlled trials rather than real-world clinical practice. However, findings were robust across multiple sensitivity analyses.
"The question isn't whether these medicines work – they clearly do," says Dr West. "The question is how we use them most effectively and sustainably within our health system. These findings suggest that treating obesity requires long-term commitment, not just from patients but from healthcare systems too."
Full citation:
West S, Scragg J, Aveyard P, Oke JL, Willis L, Haffner SJP, Knight H, Wang D, Morrow S, Heath L, Jebb SA, Koutoukidis DA. Weight regain following the cessation of medication for weight management: a systematic review and meta-analysis. BMJ, 2026. DOI: 10.1136/bmj-2025-085304
The research was funded by the National Institute for Health and Care Research (NIHR) Oxford Biomedical Research Centre.