Mounjaro Outperforms Wegovy in First Direct Weight-Loss Drug Trial—But Is It Too Good to Be True?
In a landmark head-to-head clinical trial, the weight-loss drug Mounjaro (tirzepatide) has outperformed its main rival Wegovy (semaglutide), offering greater average weight loss and improvements in several health markers. While both medications were effective, Mounjaro helped participants lose significantly more weight, deepening the debate around the future of pharmaceutical weight-loss treatment.
The trial, presented at the European Congress on Obesity in Malaga and published in the New England Journal of Medicine, tracked 750 obese adults with an average starting weight of 113kg (nearly 18 stone) over 72 weeks. Participants received the highest dose they could tolerate of either Mounjaro or Wegovy.
According to the data:
-
Mounjaro users lost an average of 20% of their body weight, compared to 14% with Wegovy.
-
32% of those on Mounjaro shed a quarter of their body weight, while only 16% reached that milestone on Wegovy.
-
Waistlines shrank by 18cm on Mounjaro, versus 13cm with Wegovy.
-
Mounjaro users also saw greater improvements in blood pressure, blood sugar, and cholesterol.
Both drugs work by mimicking natural hormones to suppress appetite and promote fat burning, but Mounjaro appears to go further—activating two appetite-related brain pathways, compared to one with Wegovy. That dual mechanism may explain its superior results.
RELATED: WeightWatchers Files for Bankruptcy Amid Rise of Weight-Loss Jabs.
Dr. Louis Aronne, who led the trial at the Comprehensive Weight Control Center at Weill Cornell Medicine in New York, highlighted the potential differences in patient needs:
“The majority of people with obesity will do just fine with semaglutide (Wegovy), those at the higher end may ultimately do better with tirzepatide (Mounjaro).”
Notably, the study was funded by Eli Lilly, the manufacturer of Mounjaro, and comes at a time of soaring demand for both drugs globally. In the UK, both are available through specialist clinics and private prescriptions. And as Prof Naveed Sattar of the University of Glasgow observed:
“In the UK, tirzepatide sales privately are now well ahead of semaglutide – that's just a reality – and this paper will accelerate that I imagine.”
Sattar also emphasized patient expectations:
“Many will be satisfied with 15% weight loss… many want as much weight loss as possible.”
Despite Mounjaro’s edge in weight loss and health outcomes, both drugs had similar side-effect profiles. Interestingly, women tended to lose more weight than men in both treatment groups.
Still, Wegovy may retain an important advantage: it’s already approved for use in cardiovascular protection, including preventing heart attacks. Mounjaro is not yet licensed for that, as equivalent trials are still underway.
RELATED: Pharmacists Warn Against Unregulated Sales of Weight-Loss Jabs.
Meanwhile, the race in obesity treatment is far from over. Researchers are testing higher doses, oral formulations, and next-generation drugs targeting different pathways. According to Prof Sattar, the field is moving so fast that:
“Obesity prevention may also be possible soon.”
That said, he cautions that focusing on medications should not distract from broader health solutions:
“It would be far better to make our society healthier to prevent more people developing obesity.”
There’s no denying the power and promise of these new weight-loss drugs. For people who’ve struggled with obesity for years, the possibility of a 15–20% weight reduction, improved health markers, and minimal side effects is understandably exciting. I’m hopeful that these medications can continue to help people lose weight safely and sustainably.
But it’s hard to shake the feeling that it all seems a little too good to be true. The funding sources, market hype, and rapid private uptake raise questions. Are we witnessing a breakthrough—or just another pharmaceutical gold rush? Only time—and long-term data—will tell.
