As weight loss injections continue to gain more popularity, researchers are getting more opportunities to study their effects. Now, the first head-to-head study between two of the most well-known medications is providing some insight on the question: Which one is best?
What are the details of the study?
Researchers studied results for those taking Zepbound and Wegovy. They found Zepound users lost nearly 50% more weight than Wegovy users.
The study, which was funded by Zepbound maker Eli Lilly, was conducted by the Comprehensive Weight Control Center at Weill Cornell Medicine and published in The New England Journal of Medicine on Sunday, May 11.
The trial included 751 people from across the U.S. who were overweight or had obesity and at least one other weight-related health problem, but not diabetes.
Zepbound vs. Wegovy
Though similar, Zepbound and Wegovy have different active ingredients. Zepbound is tirzepatide-based, while Wegovy uses semaglutide.
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More than 40% of U.S. adults have obesity, with that number tripling since 1975.
Both drugs work similarly, mimicking hormones in the gut and brain that regulate appetite and feelings of fullness. However, while both drugs target the hormone known as GLP-1, tirzepatide also targets a second hormone called GIP.
GLP-1 stimulates insulin secretion and suppresses glucagon, while also impacting appetite and slowing gastric emptying. GIP also stimulates insulin, but can enhance glucagon secretion and impact how the body stores fat.
What were the results?
By the end of the trial, researchers say those who took Zepbound lost about 20% of their body weight on average, while Wegovy users lost nearly 14% of theirs.
More than three-quarters of patients in the study reported at least one side effect, mostly mild to moderate gastrointestinal issues. About 6% of those taking tirzepatide left the trial because of the side effects, compared to 8% of those taking semaglutide.
What’s the bottom line?
Dr. Louis Aronne, who led the study, said that while it may appear one drug is more effective than the other, both are important tools for treating obesity, a disease that affects about 40% of American adults.
“The point of these medications is to improve health,” Dr. Aronna said as he presented the findings Sunday at the European Congress on Obesity in Spain. “The majority of people won’t need the most effective medication.”
At least 1 in 8 U.S. adults have reported using some type of GLP-1 drug, according to a 2024 survey by KFF.
contributed to this report.
