Ask Onix
Rapid weight rebound after discontinuing weight-loss injections
Individuals who stop taking GLP-1 weight-loss drugs like Mounjaro or Wegovy regain lost weight at a rate four times faster than those who cease traditional dieting and exercise, according to new research published in the British Medical Journal.
Study findings and weight regain rates
The analysis, based on 37 studies involving over 9,000 patients, reveals that users of these injections typically lose about 20% of their body weight. However, once treatment stops, they regain an average of 0.8 kg per month, returning to their pre-treatment weight within approximately 18 months.
In contrast, individuals who lose weight through conventional dieting and exercise regain weight more gradually-around 0.1 kg per month-though results vary.
Expert warnings and biological mechanisms
Dr. Susan Jebb, an investigator from Oxford University, cautioned that the findings, derived from clinical trials rather than real-world data, underscore the need for further research into the long-term effects of these drugs. She emphasized that users should be aware of the risk of rapid weight regain after discontinuing treatment.
Dr. Adam Collins, a nutrition expert at the University of Surrey, explained that GLP-1 drugs mimic a natural hormone that regulates hunger. Prolonged use may suppress the body's natural production of GLP-1, reducing sensitivity to its effects. When the drugs are stopped, appetite surges, increasing the likelihood of overeating.
"It was like something opened up in my mind and said: 'Eat everything, go on, you deserve it because you haven't eaten anything for so long.'"
A woman who stopped taking the jabs
NHS guidelines and prescription criteria
The NHS prescribes these drugs only to individuals with obesity-related health risks, not for cosmetic weight loss. Lifestyle changes, including healthy eating and exercise, are recommended alongside treatment to help maintain weight loss.
Many experts argue that these drugs should be considered a lifelong treatment due to the high risk of relapse. However, NHS prescriptions are not automatically continued for patients who initially obtained the drugs privately. Mounjaro has no specified time limit under NHS guidelines, while Wegovy is limited to a maximum of two years.
Potential health benefits and future research
Professor Naveed Sattar from Glasgow University noted that even short-term use of these drugs could provide health benefits, such as reducing strain on joints, the heart, and kidneys. However, he stressed the need for larger, long-term studies to confirm these effects.
Pharmaceutical companies Eli Lilly (maker of Mounjaro) and Novo Nordisk (maker of Wegovy) both emphasized the chronic nature of obesity, comparing it to conditions like diabetes or hypertension, which require ongoing management.
"When treatment is stopped, weight can return, which reflects the biology of the condition rather than a lack of effort."
Eli Lilly spokeswoman
"These findings highlight the chronic nature of obesity and suggest that ongoing treatment is necessary to maintain improvements in weight and overall health."
Novo Nordisk statement
Usage trends in the UK
Recent estimates indicate that around 1.6 million UK adults used these injections in the past year, primarily through private prescriptions. An additional 3.3 million people expressed interest in trying them within the next year, according to Cancer Research UK surveys conducted in early 2025. Usage was twice as common among women and most prevalent in individuals in their 40s and 50s.
