Mounjaro is better than Ozempic and Wegovy for weight loss, study says

People who have taken injections of tirzepatide — a component of Eli Lilly’s Monjauro drug — lost more weight and were more likely to achieve specific weight-loss goals than those who took semaglutide — a molecule found in drugs such as Novo Nordisk’s Ozempic and Wegovy — according to a new study.

Researchers at Truveta, a health data analytics company, analyzed electronic health records of more than 18,000 adults, all overweight or obese, who were using these drugs in the real world between May 2022 and September 2023. The findings were published Monday in the medical journal JAMA Internal Medicine.

Both drugs were effective: the vast majority of people taking either tirzepatide or semaglutide lost at least 5% of their starting weight after a year of use. But 82% of people taking tirzepatide achieved this important clinical milestone, compared with about 67% of those taking semaglutide.

Additionally, people taking tirzepatide were more than twice as likely to lose at least 15% of their initial weight than those taking semaglutide: about 42% compared with 18% after one year of use.

Average weight loss was also consistently greater among those taking tirzepatide over time. After three months, people taking tirzepatide had lost about 6% of their body weight on average, compared with an average loss of less than 4% among those taking semaglutide.

At six months, average weight loss was 10% with tirzepatide and about 6% with semaglutide. After one year, average weight loss was almost double for those taking tirzepatide: more than 15%, compared with about 8% for those taking semaglutide.

Tirzepatide and semaglutide mimic the effects of the gut hormone GLP-1, which stimulates the body’s production of insulin and slows the passage of food through the stomach. GLP-1 also signals the brain to help control appetite. Tirzepatide also stimulates a second gut hormone, called GIP, which may help enhance its effects.

The FDA has approved higher doses of tirzepatide and semaglutide to treat weight loss, but the new study only looked at doses to treat type 2 diabetes.

About half of the people included in this study had type 2 diabetes, while the other half had no indication of a diabetes diagnosis in their health records and were likely using these medications off-label for weight control at the discretion of their doctors.

When the results of this study were first released in a preprint last year, Novo Nordisk told CNN which was not a fair comparison.

“The semaglutide doses evaluated in this analysis have not been investigated for chronic weight management, and there are no reported comparative trials evaluating Wegovy and tirzepatide,” a spokesperson said in a statement.

According to the new study, individuals with type 2 diabetes had less significant weight loss than those without a diagnosis — but average weight loss was still greater among those taking tirzepatide.

The researchers did not track mild gastrointestinal side effects, such as nausea and vomiting, noting that these types of complaints may not be consistently captured in patient records. But the risk of more serious adverse outcomes — such as bowel obstruction, gastroparesis or pancreatitis — was found to be similar between those taking tirzepatide and semaglutide.

Along with side effects, people who didn’t lose weight while taking these drugs may be more likely to stop or switch medications, the researchers say. Discontinuation was common — more than half of patients stopped treatment before the end of the study — but rates were similar between those taking tirzepatide and those taking semaglutide.

The results of this study are in line with results from clinical trials, but the study authors note that more research is needed to compare the effects that tirzepatide and semaglutide have on other key health outcomes, such as heart-related events.

*CNN’s Brenda Goodman contributed to this report.