Weight returns 4x faster after stopping weight-loss injections, study finds
08 Jan 2026

A new study has revealed that people who stop using weight-loss injections, like Mounjaro or Wegovy, regain their lost weight four times faster than those who quit traditional dieting and exercising.

The research, published in the British Medical Journal, found that overweight individuals lose a significant amount of weight, around 20% of their body weight, while using these jabs.

However, once they stop, they gain back an average of 0.8kg every month.

Weight regain after stopping jab treatment
Regain rate

The study's findings indicate that individuals who stop using weight-loss jabs return to their pre-treatment weight in about a year and a half.

Dr. Susan Jebb from Oxford University, one of the study's investigators, stressed the need for awareness about this rapid weight regain risk after treatment ends.

However, she also noted these results are based on clinical trials rather than real-world scenarios and more research is needed on long-term effects of new slimming jabs.

Study methodology and comparison with traditional dieting
Research details

The researchers analyzed 37 studies involving over 9,000 patients to compare the effectiveness of popular weight-loss jabs with traditional dieting or other pills.

Out of these, only eight studies looked at treatment with newer GLP-1 drugs like Wegovy and Mounjaro.

These studies had a maximum follow-up period of one year after stopping medication, so the figures are estimates.

Weight regain rates after stopping jabs versus dieting
Comparison

The researchers found that while people who diet lose less weight than with the jabs, they also gain it back more slowly, about 0.1kg a month.

The NHS recommends these jabs for overweight individuals with obesity-related health risks, not just those looking to shed a few pounds.

Many experts suggest that treatment should be considered lifelong due to the risk of relapse.

How do weight-loss drugs work?
Drug action

Weight-loss jabs like Mounjaro and Wegovy mimic a natural hormone called GLP-1 that regulates hunger.

Dr. Adam Collins, a nutrition expert at the University of Surrey, explained that artificially providing GLP-1 levels several times higher than normal over a long period may cause less production of one's own natural GLP-1 and reduced sensitivity to its effects.

This could explain why weight regain is amplified once you stop taking these jabs.

Popularity and prescription guidelines for weight-loss jabs
Usage trends

According to recent estimates, around 1.6 million UK adults have used these injections in the last year, mostly through private prescriptions rather than on the NHS.

An additional 3.3 million people are interested in using "skinny jabs" over the next year, Cancer Research UK reported based on nationally representative surveys in early 2025.

However, GPs and specialist weight-management services cannot automatically prescribe Mounjaro and Wegovy even if patients have already been prescribed it privately.