People coming off weight-loss injections risk fast weight gain

New research shows that slimmers who give up weight-loss injections like Mounjaro or Wegovy can regain the weight they lost four times faster than those who give up traditional diet and exercise.

Data published British Medical Journal It suggests that overweight people lose large amounts (about a fifth of their body weight) when using injections, but gain back an average of 0.8 kilos each month after quitting.

This means they returned to their pre-treatment weight within a year and a half.

Researcher from Oxford University, Dr. “People purchasing these need to be aware of the risk of rapid weight gain once treatment ends,” warns Susan Jebb.

He emphasized that the findings were obtained from medical experiments rather than real life, and that further studies on the long-term effects of new weight-loss vaccines would be useful.

Researchers examined 37 studies with more than 9,000 patients to compare blockbuster weight-loss shots with traditional diet or other pills.

Only eight of the studies evaluated treatment with newer GLP-1 drugs such as Wegovy and Mounjaro, and the maximum follow-up period in these studies was one year after drug discontinuation; Therefore, the figures are an estimate.

People who diet instead can expect to lose less weight than on injections, but then the weight comes back more slowly (perhaps around 0.1kg per month), although this varies, the researchers say.

The NHS recommends vaccinations not only for people who want to lose a little weight, but also for people who are overweight and have health risks associated with obesity.

Doctors must also recommend lifestyle changes, which include eating healthy and getting enough exercise, to help people lose weight.

Many say treatment should be considered lifelong, given the risk of relapse.

People who have tried quitting injections describe it as “the flip of a switch and you instantly starve to death.”

One woman said: “It was like something opened up in my mind and said: ‘Eat everything, go ahead, you deserve this because you haven’t eaten anything for so long.'”

Nutritionist Dr. from the University of Surrey. Adam Collins says the way the injections work in the brain and body may explain why weight gain increases when you stop taking the injections.

They mimic a natural hormone called GLP-1, which regulates hunger.

“Artificially providing GLP-1 levels several times higher than normal over a long period of time may cause you to produce less of your own natural GLP-1 and may also make you less sensitive to its effects.

“This isn’t a problem when you’re taking medication, but when you withdraw this GLP-1 ‘correction’ the appetite is no longer kept in check and overeating becomes much more likely.”

Going cold turkey is a real challenge, he says.

“This is exacerbated if the person in question relies solely on GLP-1 to do the heavy lifting…artificially suppressing their appetite without making any dietary or behavior changes that will help them in the long run.”

Accordingly latest best guessesAround 1.6 million adults in England used these injections last year, with most bought via private prescriptions rather than on the NHS.

An additional 3.3 million people say they would be interested in using “skinny jabs” next year, according to Cancer Research UK, based on nationally representative surveys in the first quarter of 2025; This means that one in 10 adults has either tried them or wants to try them.

Use was twice as common in women than in men and was more common in people in their 40s and 50s.

Prof Naveed Sattar, from the University of Glasgow, said the injections worked quickly and could provide additional health benefits for weight loss.

“It is plausible that being lighter for two to three years due to short-term use of the injections may help slow damage to joints or the heart and kidneys. Larger and longer outcome trials will be needed to answer this question.”

“Importantly, continued use of these medications for three to four years allows people to maintain a significantly lower weight than they normally would, a benefit not typically seen in lifestyle-induced weight loss, where most people gain weight over time.”

GPs and specialist weight management services cannot automatically prescribe Mounjaro and Wegovy to patients, even if it has already been specifically prescribed.

Medicines would be available to people who need them most clinically who meet certain criteria, such as having weight-related health problems.

There is currently no set time limit for Mounjaro prescriptions on the NHS, while Wegovy can only be prescribed for a maximum of two years.

A spokesman for Eli Lilly, the pharmaceutical company that produces Mounjaro, said the use of weight-loss drugs should be accompanied by healthy nutrition, physical activity and medical monitoring.

“When treatment is stopped, weight may return, reflecting the biology of the condition rather than a lack of effort.”

Novo Nordisk, the pharmaceutical company that produces Wegovy, said: “These findings highlight the chronic nature of obesity and suggest that ongoing treatment is required to maintain improvement in patients’ weight and overall health, similar to the management of other chronic conditions such as diabetes or hypertension.”