Over half of users regain weight after stopping fat jabs – and pounds pile on in less than a YEAR

More than half of weight loss jab users regain at least some of the weight they have lost within a year of stopping the medication, new real-world analysis has shown. 

The new findings, from a large national claims database, support existing clinical studies of GLP-1 drugs, which have found that most people put weight back on once they stop treatment—with some patients regaining all the weight they had lost within just one year. 

Dr Michael Weintraub, an endocrinologist at New York University Langone Health and study lead author, said: ‘Treatment discontinuation leads to weight recurrence in clinical trials, but few real-world studies have evaluated this issue. 

‘Optimising and personalising the approach toward treating obesity and maximising gastrointestinal tolerability will maximise long-term use and long-term benefits of weight reduction,’ he added speaking to Medscape Medical News. 

The study, presented at Obesity Week 2025, Atlanta, found that weight gain after stopping the treatment was most extreme in those who had lost the most weight with the help of the drugs.

The researchers studied 1,230,320 US adults between January 2010 and June 2024 taking GLP-1 drugs for obesity or type 2 diabetes, recorded on Optum’s Market Clarity database, which links electronic health records with claims data. 

Of these, 18,228 stopped treatment after having lost at least 5 per cent body weight—the majority of which had type 2 diabetes. 

Of this total, over half of patients were taking semaglutide—the powerful ingredient behind Ozempic and Wegovy—which works by tricking the brain into thinking it’s full, consequently slashing appetite and helping users lose weight. 

One in 20 adults in the UK are now thought to be taking weight loss medication 

The remaining 56 per cent were taking either liraglutude or tirzepatide, more commonly known as Mounjaro—the ‘King Kong’ of weight loss jabs. 

On average, patients took the jabs for just over eight months, before discontinuing it. All participants included in the cohort were considered obese or overweight, with an average body mass index (BMI) of 39. 

Of the entire cohort of more than 1.2 million weight-loss jab users, over half were still using the GLP-1 drug after six months, with 38 per cent still using the jabs a year on. 

For the entire cohort, weight gain increased with time since stopping the jabs, from 4.5 per cent total body weight gain at three months to nearly 6 per cent at six months, and 7.5 per cent after a year off the jabs. 

Overall, 58 per cent of users piled the weight back on after stopping treatment. 

Dr Weintraub concluded: ‘Further areas of analysis would be to determine the differential factors in those who maintained their weight loss and those who experienced weight recurrence following the discontinuation of a GLP-1.

‘Ultimately, more strategies are needed to enhance treatment persistence to attain sustained weight loss and optimal patient outcomes.’

Asked to comment on the findings, session moderator Professor John Apolzan, expert in nutrition at the Pennington Biomedical Research Center, said: ‘I think this is a continuation of what we’re realising, that these obesity classes of drugs can’t be discontinued, as it can have negative effects and cause long-term weight regain.

‘It’s like many other prescription medications that people go on, be it hypertensives or anything like that. Once you’re on them, you tend to stay on them and you don’t go off them.’

Whilst over 40 per cent of patients were able to maintain their weight loss after stopping the jabs, researchers are not yet clear whether this was a result of lifestyle changes, or using another weight loss drug that was not captured in the claims data. 

But, researchers have speculated that the difference in how fast people put weight back on could be due to the fact that diets are harder for some people to maintain, and people looking to lose weight have to practice restraint they didn’t need on the drugs.  

Previous analysis into the efficacy of different weight loss drugs—thought to now be used by more than 2.5 million people in the UK—found that even for those taking newer more powerful jabs like Mounjaro, users put weight back on once they stopped treatment. 

Whilst patients using these drugs could expect to lose double the weight compared  with people using older jabs—around 16kg on average—they put on almost 10kg back on within a year, meaning they could expect to regain all 16kg in less than two years. 

The findings raise issues for the NHS, with guidelines stating that patients should not be on weight loss injections for more than two years. 

But the revolutionary drugs have been found to reduce the risk of a host of serious diseases, including heart disease, dementia and even cancer. 

Hailing a golden age in obesity treatment, in October 2025, leading doctors said Mounjaro and Wegovy are so effective they should be the number one treatment for obesity ‘in almost all cases’. 

In new guidance to medics, the European Association for the Study of Obesity praised the drugs’ effectiveness and significant health benefits, describing them as powerful slimming aids that can reduce the risk of associated complications, such as high blood pressure and type 2 diabetes.

It comes as a raft of long-awaited anti-obesity measures came into force earlier this month.

Under new Government laws, buy one, get one free deals on sweets, crisps, sugary drinks and other snacks have been outlawed in England, along with free refills of fizzy drinks in restaurants and cafés.

The crackdown will be followed in January by a ban on online adverts for unhealthy food and drink, and restrictions on TV advertising before 9 pm.

Ministers say the policies are designed to curb Britain’s growing obesity crisis.

A sobering report last year warned that Britain’s spiralling weight problem has fuelled a 39 per cent rise in type 2 diabetes among under-40s, with around 168,000 young adults now living with the disease.

Excess weight has also been linked to at least 13 types of cancer and is the second-biggest preventable cause of the disease in the UK, according to Cancer Research UK.