Overweight people lost 35 to 52 pounds on newly approved diabetes drug, study says

In this file photo, a waist is measured during an obesity prevention study at Rush University Medical Center in Chicago. (THE CANADIAN PRESS/AP-M. Spencer Green)

This story has been updated to show the latest news on the weight loss drug Tirzepatide.

A weekly dose of a medication recently approved by the U.S. Food and Drug Administration to treat type 2 diabetes may help adults without diabetes lose weight as well, a new study found.

Tirzepatide, which is sold under the brand name Mounjaro, was studied in people without diabetes in three dosages: 5, 10 and 15 milligrams. Participants with obesity or who were overweight and took the 5-milligram dose lost an average of 35 pounds (16 killograms), those on the 10-milligram dose lost an average of 49 pounds (22 kilograms), and participants on the 15-milligram dose lost an average of 52 pounds (23.6 kilograms).

"Almost 40% of individuals lost a quarter of their body weight," said coauthor Dr. Ania Jastreboff, codirector of the Yale Center for Weight Management in a briefing for the media.

"The data was quite impressive," said Dr. Robert Gabbay, chief medical officer of the American Diabetes Association, who spoke to CNN from the ADA's 82nd Scientific Sessions in New Orleans, where the study results were presented.

"The weight loss that they got in this study was even greater than what had been seen in the previous studies of people with diabetes," Gabbay, who was not involved with the study, said.

"The middle range of weight loss for people in this new study was 49 pounds -- 49 pounds is a lot," he said. "It's the range of weight loss that we typically think only possible through surgery."

All in all, people without diabetes lost an average of 15% to 20.9% of their starting body weight over the course of the 72-week double-blinded, randomized clinical trial, which was published Saturday in The New England Journal of Medicine. Participants who got a placebo lost between 2.4% and 3.1% of their body weight, on average.

In comparison, studies on people with diabetes who used tirzepatide found they lost an average of 15% of their starting body weight, Gabbay said.

"This is a not uncommon observation," he said. "The impact of previous weight loss medications are less effective in people with diabetes, and we honestly don't know exactly why."

However, the impact of tirzepatide on people with diabetes is still "profound," Gabbay said, "providing much more than other tools that we've had."

Self-injected dose

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."