Diabetes drugs Ozempic and Mounjaro are both widely prescribed for off-label use as weight loss drugs. However, a new study suggests that Mounjaro is a better option for people looking to lose weight quickly and efficiently.

The study by Truveta Research, a collective of more than 30 health care systems across the U.S., has yet to be peer-reviewed but has appeared in a preprint on medRxiv

“We’ve been able to compare the head-to-head efficacy of these two important medications for weight loss in advance of randomized clinical trials,” Dr. Nick Stucky, vice president of Truveta Research and a study co-author, said in a statement. “This study can help inform patient care and outcomes today, not months from now.”

Neither Ozempic manufacturer Novo Nordisk nor Mounjaro maker Eli Lilly was involved in the study. A spokesperson for Eli Lilly emphasized that the company did not recommend its product for off-label use.

According to Sarah McBane, founding associate dean of pharmacy education at UC Irvine School of Pharmacy and Pharmaceutical Sciences, the study’s findings are likely to spur conversations between patients and their health care providers.

“This study may also influence the first medication prescribed with weight loss in mind, prompting prescribers to favor tirzepatide (Mounjaro) over semaglutide (Ozempic),” McBane told Drugwatch.

Real-World Insights: What Researchers Report

The study, which claims to be the first of its kind conducted in real-world settings, compared the weight loss effectiveness of Mounjaro and Ozempic in adults who are overweight or obese. It was based on electronic health records of 41,223 patients.

The study found that Mounjaro was more effective than Ozempic in helping patients achieve significant weight loss within one year of treatment. Patients who took Mounjaro had higher success rates in achieving weight loss of 5%, 10%, and 15% compared to Ozempic users. 

Also, patients who took Mounjaro experienced “significantly larger reductions” in weight at three, six, and 12 months of treatment. At 12 months, for instance, patients taking Mounjaro lost 15.2% of their weight compared to 7.9% for those taking Ozempic.

Researchers found greater weight loss for patients without Type 2 diabetes compared to those with evidence of Type 2 diabetes — with similar effectiveness between Mounjaro and Ozempic.

Researchers said the study results are promising and suggest that Mounjaro may be a more effective option for weight loss, with consistent results across different patient populations.

How Significant Is the Study?

The study has not been peer-reviewed nor published as of December 2023. 

“The peer review process is an essential step for assuring that anything published in the scientific literature draws appropriate conclusions from the study,” McBane said.

Typically, research articles are not made public before being peer-reviewed.

“The fact that this study has been made available ahead of peer review is likely a commentary on the timeliness of the content, but we should not confuse that with thinking that it is a better study,” McBane said. “A pharmacist or physician should be prepared to let patients know that the interpretation of this information may change a little bit after the peer review process.”

She said that while the study’s results may “seem exciting,” someone using either of these drugs could experience different results. 

The researchers themselves pointed out that although both drugs are primarily intended for people with Type 2 diabetes, half of the participants used them only for weight loss. This factor might have influenced the outcomes. 

Truveta researchers found greater weight loss for patients without Type 2 diabetes compared to those with evidence of Type 2 diabetes, with similar effectiveness between Mounjaro and Ozempic.

Two related weight loss drugs — Eli Lilly’s Zepbound and Novo Nordisk’s Wegovy — are currently in a head-to-head clinical trial in obese and overweight patients. Eli Lilly is funding the study, and results are not expected until 2025.