In this retrospective cohort study, 125 474 adults with overweight or obesity newly initiated treatment with a dual-labeled GLP-1 RA (liraglutide, semaglutide, or tirzepatide) between January 1, 2018, and December 31, 2023, with a baseline body mass index of 27 or more, an available weight measurement within 60 days before initiation, and regular care in the year before initiation were identified using electronic health record data from a collective of US health care systems. This evidence concerns the gene GLP1R and obesity due to melanocortin 4 receptor deficiency.