New real-world analysis shows that more than half of individuals using weight loss injections regain at least some of the weight within a year of discontinuation. The findings, derived from a large national claims database, corroborate prior clinical studies on GLP-1 drugs, which consistently indicated that most people experience weight regain once treatment ceases, with some regaining all lost weight within twelve months.

Dr. Michael Weintraub, an endocrinologist at New York University Langone Health and lead author of the study, emphasized that while clinical trials demonstrated weight recurrence after stopping treatment, few real-world analyses had explored this effect. He advocated for personalized obesity treatments to maximize gastrointestinal tolerability, ensuring longer-term use and sustained weight loss benefits.

The study, presented at Obesity Week 2025 in Atlanta, highlighted that weight regain was most pronounced among those who had achieved the greatest weight loss on the drugs. Researchers examined data from 1,230,320 US adults between January 2010 and June 2024 taking GLP-1 drugs for obesity or type 2 diabetes. Among this cohort, 18,228 individuals had discontinued treatment after losing at least 5 percent of their body weight, many of whom also had type 2 diabetes.

Over half of the patients were using semaglutide, the active ingredient in Ozempic and Wegovy, which signals satiety to the brain and reduces appetite. The remaining 56 percent were prescribed either liraglutide or tirzepatide (Mounjaro), sometimes called the 'King Kong' of weight loss injections. On average, participants used these jabs for just over eight months before stopping, with all having a body mass index (BMI) of 39 or higher.

Among the cohort, more than half continued GLP-1 use after six months, with 38 percent still on the medication after a year. For those who stopped, weight gain progressively increased: 4.5 percent of total body weight regained at three months, nearly 6 percent at six months, and 7.5 percent after a year. Overall, 58 percent experienced weight regain following discontinuation.

Dr. Weintraub suggested future research focus on factors contributing to weight maintenance versus weight recurrence after stopping GLP-1 drugs. Professor John Apolzan of the Pennington Biomedical Research Center noted that obesity medications, like other chronic condition treatments, are often not meant to be discontinued, as cessation can lead to negative effects and long-term weight gain.

While over 40 percent of patients maintained their weight loss after stopping the jabs, researchers remain uncertain whether this was due to lifestyle changes or other weight loss medications not recorded in the data. Differences in weight regain could stem from the difficulty of maintaining diets and self-restraint without the drug's support.

Previous analyses indicate that even users of newer, potent jabs like Mounjaro tend to regain weight after discontinuation. While patients could expect to lose twice as much weight as older drugs (an average of 16kg), many regained almost 10kg within a year, suggesting full regain within two years.

These findings present challenges for health systems like the NHS, whose guidelines currently limit weight loss injections to two years. This contrasts with the drugs' proven ability to reduce risks of heart disease, dementia, and cancer. Leading medical professionals hailed a 'golden age in obesity treatment,' suggesting Mounjaro and Wegovy should be primary therapies 'in almost all cases,' according to new guidance from the European Association for the Study of Obesity.

In related developments, the UK government has introduced anti-obesity measures, banning 'buy one, get one free' deals on sweets, crisps, sugary drinks, and free refills in eateries. Further crackdowns are expected in January with bans on online advertising of unhealthy foods and TV ads before 9 pm. These policies address Britain’s escalating obesity crisis, which has fueled a 39 percent rise in type 2 diabetes among under-40s, affecting roughly 168,000 young adults, and links excess weight to at least 13 cancers.