A genome-wide association study of nearly 28,000 patients identified genetic variants in the GLP1R and GIPR genes that influence the efficacy and side effects of GLP-1 receptor agonists. A specific missense variant in GLP1R was linked to significantly greater weight loss, while variations in both GLP1R and GIPR were associated with the likelihood of experiencing nausea or vomiting. These findings suggest that genetic screening could help predict individual patient responses to popular obesity drugs like semaglutide and tirzepatide.