People who stop taking weight-loss injections such as semaglutide (Wegovy) and tirzepatide (Mounjaro) can regain lost weight four times faster than those using traditional diet and exercise, according to NIHR-funded research led by the University of Oxford.
The study, published in the British Medical Journal, analysed 37 studies involving over 9,000 participants who discontinued weight management medicines after an average of 39 weeks of treatment. Participants were tracked for 32 weeks post-treatment.
Key findings include:
- Weight regain averaged 0.8 kg (1.8 lbs) per month after stopping injections
- Most participants returned to their starting weight within 18 months
- Regain was 0.3 kg per month faster than traditional dieting and exercise, regardless of initial weight loss
The research highlights the importance of ongoing clinical oversight and behavioural support, as 9 in 10 UK users currently buy these drugs privately, often without NHS guidance.
Dr Sam West, Lead author of the study and Postdoctoral Researcher at the Nuffield Department of Primary Care Health Sciences, University of Oxford, said:
"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.
"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 study was funded by NIHR Oxford Biomedical Research Centre and NIHR Oxford Health BRC, with support from NIHR Applied Research Collaboration Oxford and Thames Valley.
This follows another NIHR-backed review in Obesity Reviews, which found gaps in nutritional guidance for people using weight-loss drugs. These medicines can reduce calorie intake by 16–39%, but evidence suggests up to 40% of weight lost may be lean body mass, raising concerns about muscle and nutrient adequacy.
Experts say the findings underscore the need for long-term strategies to maintain weight loss and protect health after stopping medication.
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