People who stop taking weight-loss medications tend to regain weight quickly — and significantly faster than those who finish structured diet and exercise programmes

— according to a major new analysis led by researchers at the University of Oxford.

The findings, published today in ‘The BMJ’, raise important questions about how newer weight-loss drugs such as semaglutide and tirzepatide are being used, particularly as real-world data suggests that around half of patients discontinue these treatments within a year.

Rapid regain after medication stops

The Oxford team reviewed data from 37 clinical studies involving 9,341 adults who had taken weight-management drugs and then stopped. On average, participants regained about 0.4 kg (0.9 lb) per month after discontinuing medication. At that pace, most would return to their starting weight within 18 to 24 months.

For newer GLP-1 receptor agonists — including semaglutide and tirzepatide — weight regain was even faster, averaging 0.8 kg (1.8 lb) per month. Based on current evidence, people using these drugs are projected to return to their pre-treatment weight in roughly a year and a half, although longer-term data is still limited.

Faster regain than diet-based programmes

Crucially, the researchers found that weight regain after stopping medication occurred around 0.3 kg per month faster than after completing behavioural weight-loss programmes such as diet and physical activity support. This difference was seen regardless of how much weight people initially lost.

While combining medication with behavioural support helped people lose more weight during treatment, it did not slow down weight regain once the drugs were stopped.

Health benefits fade too

The analysis also showed that improvements in key cardiometabolic markers — including blood sugar (HbA1c), fasting glucose, blood pressure, cholesterol and triglycerides — tended to disappear after treatment ended. These markers were estimated to return to baseline levels within about 14 to 18 months of stopping medication.

Obesity as a long-term condition

Lead author Dr Sam West from Oxford’s Nuffield Department of Primary Care Health Sciences stressed that the findings should not be seen as a failure of the drugs themselves.

“These medicines are transforming obesity treatment and can produce substantial weight loss,” he said. “But our analysis shows that people tend to regain weight rapidly after stopping — faster than we see with behavioural programmes. This reflects the reality that obesity is a chronic, relapsing condition, not something that can be fixed with short-term treatment alone.”

Why the rebound may be faster

Senior author Associate Professor Dimitrios Koutoukidis suggests one explanation is behavioural.

“When people lose weight through diet and activity changes, they’re actively practising habits that help them maintain that loss,” he said. “With medication, weight loss can happen without developing those strategies, so when treatment stops, people may be more vulnerable to rapid regain.”

The findings also have implications for healthcare planning. Earlier cost-effectiveness estimates by NICE assumed weight would return to baseline over two to three years. This analysis suggests it may happen closer to 18 months, reinforcing the NHS’s cautious approach of prioritising patients with severe or complex obesity.

Private use raises concerns

The researchers note that around 90% of people currently using weight-loss drugs in the UK obtain them privately, often without long-term clinical follow-up or structured behavioural support.

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.'

Limitations and next steps

The authors acknowledge several limitations, including relatively short follow-up periods after stopping treatment and limited long-term data on newer drugs. Most studies were conducted in controlled trial settings rather than routine clinical practice. Even so, results were consistent across multiple analytical approaches.

“The question isn’t whether these medicines work — they clearly do,” said Dr West. “The real challenge is how to use them effectively and sustainably. Treating obesity requires long-term commitment from both patients and health systems.”

The study, “Weight regain following the cessation of medication for weight management: a systematic review and meta-analysis,” was funded by the National Institute for Health and Care Research (NIHR) Oxford Biomedical Research Centre and is published in ‘The BMJ’.