A new study from the University of Cambridge suggests that people using weight loss injections, often called “obesity jabs,” regain the majority of the weight they lose within a year of stopping treatment. Researchers found that, on average, participants regained 60% of their lost weight within 52 weeks.
Experts warn that if the regained weight is primarily fat, patients could end up in a worse body composition than before starting the treatment, potentially affecting long-term health.
How Weight Loss Jabs Work
These injections belong to a class of drugs known as GLP-1 receptor agonists. They mimic the hormone GLP-1, which regulates blood sugar and insulin levels. Originally developed for type 2 diabetes, drugs like semaglutide (Wegovy) and tirzepatide (Mounjaro) are now approved in the NHS for obesity management.
Beyond weight loss, a separate U.S. study suggests these drugs may help prevent and treat addictions, including alcohol, nicotine, cannabis, cocaine, and opioids. Researchers believe GLP-1 receptor agonists influence the brain’s reward pathway, reducing cravings. The study, involving more than 600,000 U.S. veterans, found reduced risk of substance misuse in those without prior addictions and fewer emergency visits and overdoses in those already addicted.
Key Findings on Weight Regain
Published in eClinicalMedicine, the Cambridge study analyzed six trials with over 3,200 participants. It found that although most weight is regained after stopping the jabs, the regain tends to plateau around 75% of the initial weight lost by 60 weeks, meaning about 25% of the loss could be maintained long-term.
Brajan Budini, a medical student at Cambridge, explained:“Even though people regain most of the weight they have lost, some weight loss is maintained. However, we don’t yet know whether lean mass is preserved. If the regained weight is disproportionately fat, individuals may be worse off in their fat-to-lean ratio, which could negatively affect health.”
The researchers emphasized the need for further studies to explore how these drugs impact body composition during and after treatment.
Implications for Addiction Prevention
The U.S. study, published in the British Medical Journal, followed veterans for up to three years. Those without a history of substance abuse experienced a 14% lower risk of substance use disorders, including reductions of 18% for alcohol, 14% for cannabis, 20% for cocaine and nicotine, and 25% for opioids.
Among participants with existing substance use disorders, starting the jabs was associated with a 31% lower risk of emergency department visits, hospitalizations, overdoses, and drug-related deaths. While the study mainly involved older men, the results were similar for women.
These findings highlight both the potential benefits and limitations of GLP-1 receptor agonists, emphasizing the importance of long-term monitoring and further research into their effects on body composition and addiction prevention.
