An expert calls these findings ‘the best seen so far with any anti-obesity medication.’ Diet and exercise changes also played key roles.
Tirzepatide, the active ingredient in the diabetes drug Mounjaro, helped people lose more than 60 pounds (lb), or at least one-quarter of their body weight, when used along with intensive lifestyle changes, according to a new study.
Researchers asked 806 obese or overweight participants without type 2 diabetes to dramatically overhaul their eating and exercise habits for three months. Aided by a low-calorie diet and frequent counseling sessions, a total of 579 people managed to reduce their body weight by at least 5 percent. Scientists then randomly assigned individuals in this group to take weekly injections of tirzepatide or a placebo for 72 weeks.
At the start of the study, people weighed an average of 241 lb. By the end, those on tirzepatide lost almost 27 percent of their total body weight on average, or about 64 pounds, according to the results, published in Nature Medicine. By comparison, participants who got placebo shots shed 9 lb, or about 4 percent of their weight.
“The results seen with tirzepatide are the best seen so far with any anti-obesity medication and are similar to results seen at one year with bariatric surgery,” says Adam Gilden, MD, an associate professor and the associate director of the weight management and wellness clinic at the University of Colorado School of Medicine in Aurora, who wasn’t involved in the new study.
What Is Tirzepatide?
Tirzepatide is the first drug in a new family of medicines that target two hormones — glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) — that are involved in maintaining healthy blood sugar levels and sending signals from the gut to the brain when people are full.
The U.S. Food and Drug Administration (FDA) approved tirzepatide as a type 2 diabetes treatment in May 2022. The FDA has not yet okayed the medication as a weight-loss treatment.
But Mounjaro's producer, Eli Lilly, which funded the new research, asked the FDA for this approval earlier this year on the basis of results from a different study involving people with obesity and type 2 diabetes.
Intensive Lifestyle Changes Played a Role in the Remarkable Weight Loss
Part of the dramatic weight loss results seen in the new study may be due to the intensive lifestyle changes people had to make before they could receive tirzepatide, says the lead author of the study, Thomas Wadden, PhD, a professor of psychology in psychiatry at the Perelman School of Medicine at the University of Pennsylvania in Philadelphia. Dr. Wadden serves on advisory boards for Novo Nordisk, a maker of the weight loss drug Wegovy (semaglutide), and WW, the company formerly known as Weight Watchers.
“The drug alone did not produce the full reduction in weight,” Wadden says. “You can’t eliminate the contribution of initial lifestyle counseling to the total weight loss achieved.”
But the study does suggest that tirzepatide helped participants continue weight loss that was kick-started by lifestyle changes, says Melanie Jay, MD, an associate professor and an obesity researcher at the New York University Grossman School of Medicine in New York City, who wasn’t involved in the new study.
“They were all responders to lifestyle-based therapy, and the medication not only prevented weight regain, but participants continued to lose weight,” says Dr. Jay, who has no financial ties to companies involved in weight loss interventions.
In a separate study published last year in the New England Journal of Medicine, people with overweight or obesity who took tirzepatide for 72 weeks without making any lifestyle changes lost an average of almost 21 percent of their body weight on the highest dose of the medicine.