Zepbound vs. Wegovy: New clinical trial says this weight-loss medication sheds more pounds

After injecting the medications weekly for nearly 17 months, patients who took Zepbound lost 20.2% of their body weight (50.3 pounds) on average, while Wegovy patients lost 13.7% (33.1 pounds), Lilly announced in a Dec. 4 news release. In addition, Zepbound yielded a 47% greater relative weight loss over its rival, and 31.6% of Zepbound patients lost at least 25% of their body weight, compared to 16.1% of Wegovy users.

“Given the increased interest around obesity medications, we conducted this study to help health care providers and patients make informed decisions about treatment choice,” Dr. Leonard Glass, senior vice president of global medical affairs at Lilly Cardiometabolic Health, said in the news release. “Zepbound is in a class of its own as the only FDA-approved dual GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1) receptor agonist obesity medication, and it’s changing how millions of people manage this chronic disease.”

The trial involved 751 U.S. adults 18 and older who had either obesity or overweight with at least one of the following medical conditions: heart disease, high blood pressure, high cholesterol, or obstructive sleep apnea. They received the maximum tolerated dose of Zepbound (10 mg or 15 mg) or Wegovy (1.7 mg or 2.4 mg) for 72 weeks. (No participant had diabetes; Lilly markets tirzepatide as Mounjaro to people with Type 2 diabetes, while Novo Nordisk does the same for semaglutide as Ozempic.)

The results have not yet been peer-reviewed. However, Lilly indicated they would in 2025 be published in a peer-reviewed journal and presented at an unspecified medical meeting.

Lilly sponsored the clinical trial, the goal of which, the company said, “was to demonstrate Zepbound’s superiority in percent change from baseline in body weight at 72 weeks compared to Wegovy.” This shouldn’t necessarily raise eyebrows, says Dr. W. Scott Butsch, director of obesity medicine at Cleveland Clinic’s Bariatric and Metabolic Institute.

“We should always look at the funding source as a potential bias of the study,” Butsch tells Fortune via email. “But this study was well-designed, and we should believe the data.”

It’s not uncommon for pharmaceutical companies to spearhead such research, says Dr. Nisha Patel, medical director of the Obesity Medicine and Metabolic Health Program within the transplant department at California Pacific Medical Center in San Francisco.

“These trials are usually conducted with the utmost scientific rigor,” Patel tells Fortune via email.

What’s more, the trial results are similar to those of a study—not financed by Lilly—published earlier this year in the journal JAMA Internal Medicine, Dr. Holly Lofton, director of the NYU Langone Health Weight Management Program, points out to Fortune. That research showed that 42.3% of people taking tirzepatide, the generic name for Zepbound, lost at least 15% of their body weight within a year, compared to 18.1% of people taking semaglutide, the generic name for Wegovy.

Should I take Zepbound instead of Wegovy?

Both Zepbound and Wegovy are prescription medications, so you must consult your health care provider if you have concerns about taking one over the other. Not to mention, Patel says, “it’s still important to understand that we have multiple therapy options for the treatment of obesity.” Your doctor can help you determine which may be appropriate for you, given your weight-loss goals and medical history.

And while the results of Lilly’s trial are promising, they shouldn’t be your only consideration in requesting a weight-loss medication, Lofton says.

“Both drugs demonstrate meaningful weight loss of over 10%, which can improve or ameliorate many weight-related medical conditions,” Lofton tells Fortune via email. “Prescribers and patients should always consider safety, efficacy, and accessibility of the medication when deciding which drug is best for the patient.”

Butsch echoes, “From the patient’s perspective, I don’t think that these study results will change the public demand for tirzepatide, nor result in switching medications. It reinforces that there are currently two highly effective medications, but so many factors—cost, coverage, et cetera—that are barriers to appropriate access.”

For more on weight management:

• Hims & Hers Super Bowl ad slams pricey pharma industry—and fumbles FDA warnings on compounded GLP-1 drugs
• Most Americans who want to lose weight don’t want to take GLP-1 drugs like Wegovy and Zepbound, new survey says
• The 5 biggest weight loss myths that ‘need to die,’ according to an obesity doctor
• GLP-1 drugs like Wegovy are all the rage—but people are quitting them too fast to achieve meaningful weight loss, finds 170,000-patient study
• This is the best time of day to exercise for people living with obesity, new study shows