Málaga, Spain: In the first direct comparison between two blockbuster weight-loss drugs, Mounjaro (tirzepatide) has proven more effective than Wegovy (semaglutide), delivering significantly greater weight reduction over 72 weeks.
According to findings presented at the European Congress on Obesity in Malaga and published in the New England Journal of Medicine, participants using Mounjaro lost an average of 20 percent of their body weight, compared to 14 percent for those on Wegovy.
Head-head weight-loss trial
The trial, sponsored by Mounjaro’s manufacturer Eli Lilly, involved 750 obese adults with an average weight of 113kg (approximately 18 stone). Participants were given the highest dose of the drug they could tolerate. Results showed that 32 percent of Mounjaro users lost a quarter of their body weight, double the 16 percent recorded among Wegovy users.
Additionally, Mounjaro led to greater average waistline reductions (18cm vs. 13cm) and showed superior results in improving blood pressure, cholesterol, and blood sugar levels. Side effects were similar between the two drugs, and women in general lost more weight than men.
The difference in effectiveness lies in how the drugs operate. Wegovy mimics a natural hormone that activates one appetite-control mechanism in the brain after eating, while Mounjaro activates two, leading to enhanced fat burning and reduced food intake.
Dr. Louis Aronne, who led the study at the Comprehensive Weight Control Center at Weill Cornell Medicine, stated that most obese patients would benefit from semaglutide (Wegovy), but those needing more significant weight loss might do better with tirzepatide (Mounjaro).
In the UK, both drugs are available through specialist weight-management services and private sales.
Prof Naveed Sattar of the University of Glasgow noted that private sales of tirzepatide in the UK now exceed those of semaglutide and predicted the study will likely widen that gap. He acknowledged that while many patients are satisfied with 15 percent weight loss, others aim for more aggressive results.
However, Wegovy has been approved for additional uses, such as reducing the risk of heart attacks, whereas Mounjaro has not yet completed the equivalent cardiovascular trials.
The weight-loss drug landscape is evolving rapidly, with researchers testing higher doses, new delivery methods like oral pills, and novel compounds that target the body differently.
According to Prof Sattar, the scale of ongoing research suggests that obesity prevention through medication may become possible, though he emphasized the importance of societal health reforms to reduce obesity rates without pharmaceutical dependence.
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