For the new study, weekly injections of tirzepatide were tested in more than 2,500 people without diabetes who had a body mass index (BMI) over 30 or who were over 27 BMI and had at least one weight-related health condition such as high blood pressure, high cholesterol or cardiovascular disease. A measure of a person's height-to-weight ratio, a BMI of 25 or higher is considered overweight in adults.
At the start of the study, the participants had an average weight of 231 pounds (104.8 kilograms) and average BMI of 38.
Adults in the study injected themselves with tirzepatide or a placebo once a week, using "a small penlike device with a tiny, tiny needle," Gabbay said. "The prick from that needle is less painful than, for example, people that prick their fingers to measure blood glucose."
People in the study also received counseling sessions to help them stay on a healthy diet with a daily 500-calorie deficit, as well as at least 150 minutes of physical activity each week. While that certainly helped, it does not explain the magnitude of the weight loss seen in the study, Gabbay said.
"The kind of weight loss that we see when people exercise and change their calorie intake is somewhere in the order of 5% to 7%," he said. "This study showed a profoundly greater weight loss, far above what we would imagine with lifestyle changes."
The most common side effects reported were nausea, diarrhea and constipation. Between 2.6% and 7.1% of the participants discontinued treatment due to adverse events.
Mounjaro carries a boxed warning about thyroid tumors and should not be used by people with a family history of certain thyroid conditions.
"Obesity should be treated like any other chronic disease -- with effective and safe approaches that target underlying (causes of) disease ... and these results underscore that tirzepatide may be doing just that," Jastreboff of the Yale Center for Weight Management said in an American Diabetes Association news release.
"These results are an important step forward in potentially expanding effective therapeutic options for people with obesity."