Weight-loss medications are becoming increasingly popular as tools to combat obesity, but the question remains: Are some more effective than others? This question was at the heart of a recent study published in The New England Journal of Medicine, which compared two such medications, tirzepatide (known as Zepbound) and semaglutide (known as Wegovy), over a 72-week period. The study, dubbed SURMOUNT-5, included 751 participants from the U.S. and Puerto Rico, all of whom were dealing with obesity but did not have type 2 diabetes.
Dr. Louis Aronne from Weill Cornell Medicine, who played a key role in the research, noted that people often ask which drug is more effective. This study provided a chance to directly compare them. The results mirrored what had been observed when these drugs were tested individually. The findings indicated that tirzepatide led to more significant weight loss, with participants losing around 50 pounds, which is about 20.2% of their body weight.
The trial showed that 32% of those taking tirzepatide lost at least a quarter of their body weight, while about 16% of semaglutide users achieved similar results. Participants on tirzepatide also experienced a greater reduction in waist size compared to those on semaglutide. Dr. Aronne attributed tirzepatide’s success to its “dual mechanism of action.”
Semaglutide works by activating receptors for a hormone called GLP-1, while tirzepatide also mimics another hormone called glucose-dependent insulinotropic peptide (GIP). Together, these actions help reduce hunger, lower blood sugar levels, and influence fat metabolism. Beyond weight loss, semaglutide has shown potential benefits for cardiovascular health and other conditions.
Notably, both medications had similar side effects, such as nausea and abdominal pain, affecting a significant number of participants. Dr. Ada Londono from PlushCare highlighted that while the results align with previous trials, the study was funded by Eli Lilly, the company behind Zepbound, which could raise questions about potential bias.
The study’s open-label design, where participants knew which medication they were taking, was acknowledged as a limitation that could introduce bias. Despite these concerns, Dr. Rekha Kumar from the weight care program Found emphasized the importance of choosing a weight-loss medication that aligns with a patient’s health needs and personal goals.
Dr. Kumar mentioned that both Wegovy and Zepbound have shown clinically significant weight reduction. For instance, in cases of fatty liver, the choice of medication might depend on which one is proven to work best for liver issues. Researchers are eager to explore new drugs, such as retatrutide, that mimic multiple hormones to further improve outcomes.
While current medications like tirzepatide and semaglutide are highly effective, Dr. Aronne acknowledged that not everyone responds to them. The goal is to continue improving and finding better solutions for those who need them. Novo Nordisk, the maker of Wegovy, stated that the comprehensive management of obesity involves more than just weight reduction.
