(WGN Radio) – A new version of the diabetes drug Mounjaro – which people have been seeking out as a weight loss drug all year – is now officially approved by the FDA to help patients do just that.

The drug, made by Eli Lilly, is marketed as Zepbound. Also known as tirzepatide, it has helped dieters lose as much as 40 to 60 pounds in testing.

The weekly injection of Zepbound works by mimicking the hormones that kick in after you eat, which regulate appetite and give you a feeling of fullness. In addition to suppressing appetite, it also slows down the rate your stomach empties, making you feel full longer, explained Dr. Cecilia Low Wang, with UCHealth’s Diabetes and Endocrinology Clinic.

The drug’s ingredients work much like semaglutide, which can be found in Wegovy and Ozempic.

“This would be the most highly efficacious drug ever approved for the treatment of obesity,” said Dr. Fatima Cody Stanford, an obesity medicine expert at Massachusetts General Hospital in Boston.

Dr. Veronica Johnson, an obesity medicine specialist at the Northwestern Medicine Center for Lifestyle Medicine, said the drug was just about as effective as metabolic and bariatric surgery. It gives patients an alternative to going under the knife to treat obesity, and all the medical conditions that come with excess weight.

Dr. Johnson encouraged people to think of Zepbound as a potential solution to the complex condition of obesity.

“Obesity is far more complicated than just eat less, move more,” she said. “We have clear hormones in our body and other determinants and contributors that make it harder for us to manage our weight with just lifestyle modifications.”

The drug, while FDA-approved, may not be easier to access. A month’s supply costs about $1,000 a month out of pocket. Tirzepatide is also still in short supply, according to FDA tracking.

Another challenge is that patients may need to be paying that price for a long time, if not forever.

“At the moment, the understanding is that tirzepatide and semaglutide need to be taken for a lifetime,” Dr. Leana Wen, a professor of health policy and management at George Washington University, told CNN. “If they are stopped, much of the weight loss is reversed.”

Hear more about Zepbound from Dr. Johnson in an interview with WGN Radio below:

Zepbound is the latest diabetes drug approved for chronic weight management, joining Novo Nordisk’s Wegovy, a high-dose version of its diabetes treatment Ozempic. Both are weekly injections.

Side effects of the new weight-loss drug include vomiting, nausea, diarrhea, constipation and other gastrointestinal problems. In the most recent published trial, about 10% of people taking tirzepatide dropped out of the study because of such problems, compared to about 2% of people taking dummy shots.

The Associated Press contributed to this report.