Weight Regain Accelerates After Stopping Slimming Injections, Study Suggests

People who stop using popular weight loss injections may regain weight far more quickly than those who rely on traditional dieting and exercise, according to new research that has prompted experts to urge caution and better long term planning around these treatments.

An analysis published in the British Medical Journal found that people who discontinue injectable weight loss drugs regain weight at around four times the speed of those who stop conventional diet based approaches. The findings are based on a review of existing clinical trial data and highlight concerns about what happens once treatment ends.

The researchers examined data from 37 studies involving more than 9,000 overweight or obese participants. These studies compared outcomes from weight loss injections with those achieved through calorie controlled diets, exercise programmes or older weight loss medications. The results showed a clear pattern. While injections were associated with much greater initial weight loss, the rebound after stopping treatment was also significantly faster.

Participants using newer injectable drugs such as Wegovy and Mounjaro typically lost around one fifth of their body weight during treatment. However, once the medication was discontinued, they regained an average of about 0.8 kilograms per month. At that rate, many returned to their pre treatment weight within roughly 18 months.

By contrast, people who lost weight through dieting and exercise tended to shed fewer kilograms overall. But after stopping, their weight regain was slower, averaging closer to 0.1 kilograms per month, although individual experiences varied widely. This difference in regain speed is what led researchers to describe the effect as roughly four times faster for injection users.

One of the study’s authors, Susan Jebb from Oxford University, warned that people considering these medications need to be fully informed about the likelihood of rapid weight regain if treatment is stopped. She emphasised that injections should not be seen as a short term fix, but rather as part of a longer term weight management strategy.

Dr Jebb also stressed that the findings are based on clinical trials rather than everyday real world use. Only eight of the studies included focused on the newer GLP 1 based drugs, and the longest follow up period after stopping treatment was one year. As a result, the monthly regain figures are estimates rather than precise predictions.

The study does not suggest that slimming injections are ineffective. On the contrary, the scale of weight loss achieved during treatment is far greater than with most traditional methods. However, the research highlights a key challenge. These drugs appear to work by suppressing appetite and altering metabolism, effects that diminish once the medication is withdrawn.

Experts say this raises important questions about how long people should remain on the injections, how they should transition off them, and what additional support is needed to maintain weight loss. Some argue that long term or even lifelong use may be necessary for certain patients, similar to treatments for chronic conditions.

The findings also underline the importance of lifestyle changes alongside medication. Without sustainable habits around diet, physical activity and behaviour, weight regain appears likely once the pharmacological support is removed.

Researchers have called for longer follow up studies to better understand the long term impact of these drugs, including how best to prevent rapid rebound weight gain. As demand for slimming injections continues to grow, the study serves as a reminder that dramatic weight loss can come with equally dramatic challenges once treatment stops.