Overweight and obese adults who took the injected medication Mounjaro lost more weight and were more likely to meet specific weight loss targets than people on a similar competitor, Ozempic, according to a new study of people taking the drugs in the real world.
Both Ozempic, or semaglutide, and Mounjaro, or tirzepatide, 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 boost its effects.
The drugs are prescribed to treat type 2 diabetes but have gained new popularity because they may also help people lose substantial amounts of weight.
The new study is a preprint that has not been peer-reviewed or published in a professional journal. Its results are in line with observations from clinical trials, and many doctors had suspected that tirzepatide might be more potent after seeing the results in their diabetes patients. But so far, there haven’t been many studies that have compared the drugs head-to-head, especially in people who don’t have diabetes. One such investigation is underway, but results aren’t expected for more than a year.
“Over 70% of American adults have overweight or obesity, and so there’s this huge potential for these medications to be used and [there’s] really a lack of information,” said lead study author Dr. Patricia Rodriguez, a senior applied scientist at Truveta Research.
The study wasn’t sponsored by either of the drugs’ manufacturers. Instead, it was initiated by Truveta, a data analytics company owned and operated by 30 US health care systems. Truveta combines anonymous patient records from these hospitals and uses them to answer research questions.
Comparing weight loss medications
Because of their weight-loss benefits, the US Food and Drug Administration has approved higher doses of both tirzepatide and semaglutide for weight loss under the names Zepbound and Wegovy, respectively. The new study looked only at the doses approved to treat type 2 diabetes, which may limit its conclusions. The records spanned the period between May 2022 and September 2023.
Rodriguez and her team combed through thousands of patient records to find overweight and obese adults on Mounjaro or Ozempic.
Of the more than 18,000 people included in the study, just over half – 52% – had type 2 diabetes. The other 48% had no history of diabetes documented in their medical records, so researchers reasoned that this group of more than 9,000 people was probably taking the medications off-label at their doctor’s discretion, solely for weight loss.
People lost more weight the longer they stayed on the medication, but many did not continue taking these drugs. Roughly half of people included in the study discontinued them during the study period.
The authors note that it’s hard to say why people stopped filling their prescriptions. Both medications in the study were in shortage, and so they may have been difficult to find.