Research suggests that people carrying variations in two genes linked to appetite and digestion can lose more weight when using medications such as Wegovy and Mounjaro. The findings, detailed in the journal Nature, could explain the disparity in weight loss results among users and why some experience debilitating side effects like nausea and vomiting.

The study utilized data from 15,000 individuals who had undergone 23andMe genetic testing. Researchers identified a genetic pattern suggesting that a specific variant—carried by 64% of people with European ancestry but only 7% of African Americans—leads to an average of 0.76kg in extra weight loss. Those with two copies of the gene can double that amount. Conversely, another variant was linked to a nearly 15-fold increase in the likelihood of severe vomiting for Mounjaro users.

However, experts like Dr. Marie Spreckley from the University of Cambridge remind us that genetics is only one piece of a complex puzzle. Clinical outcomes are also driven by sex (women are twice as likely to see significant results), age, and behavioral factors such as diet and exercise. While the genetic effect is "not trivial," lifestyle remains a primary driver of long-term success.