Rosie O'Donnell credits Mounjaro for 'never felt better' at 64

Two weeks later, the scale delivered a scare. “Cut to two weeks later, I get on the scale. I call my doctor crying, I must have cancer. I've lost 12 pounds, and I haven't done anything,” she said. “I had never lost weight for no reason,” she added. Losing weight, she said, had always been difficult, even when she was actively trying.

The FDA approved Mounjaro for type 2 diabetes in 2022 and, a year later, cleared the same drug for chronic weight management under the brand name Zepbound. Its active ingredient is tirzepatide.

Tirzepatide activates receptors for GLP-1, a gut hormone that regulates blood sugar and appetite, and also for a second hormone, GIP. Semaglutide, the active ingredient in Ozempic and Wegovy, activates only the GLP-1 receptor. Nausea and diarrhea are the common side effects of both drugs.

O'Donnell is one of several celebrities to speak openly about GLP-1 medications. Eric Stonestreet, the “Modern Family” actor, told Business Insider in May 2025 that Mounjaro, prescribed for his diabetes, pushed him toward a healthier routine. He started moving 150 minutes a week. “All of a sudden, I felt like I needed to be accountable to it, because it's showing up every day to do something for me,” Stonestreet said.

Serena Williams said in August 2025 that she turned to a GLP-1 after struggling to lose weight following childbirth despite regular exercise and healthy eating. She said she lost more than 31 pounds. Oprah Winfrey said in January she regrets not trying GLP-1s sooner. “I think about the wasted years,” Winfrey said.