The medical community has long observed a significant disparity in how individuals respond to glucagon-like peptide 1 (GLP-1) receptor agonists, such as semaglutide and tirzepatide. While these weight-loss jabs have revolutionized obesity treatment for millions, the underlying reasons for varying efficacy and side-effect profiles have remained largely speculative.
On April 8, 2026, Nature published a study that identified specific genetic markers that may dictate a patient’s journey with these medications. Analyzing a massive dataset involving nearly 28,000 patients, the investigation focused on how variations in genes related to gut hormone pathways—the systems responsible for managing appetite, insulin production and the speed of digestion—impact drug performance.
GLP-1
Two primary genetic variants of interest were identified. The first, a GLP-1 receptor variant labeled rs10305420, was linked to enhanced weight reduction. Individuals carrying this specific variant tended to lose more weight than those without it. The second variant, rs1800437, was specifically associated with adverse reactions, such as nausea and vomiting, particularly in patients utilizing tirzepatide. Interestingly, this second variant did not seem to influence the actual amount of weight lost, suggesting that the mechanisms for drug efficacy and drug intolerance may be genetically distinct.
Despite these breakthroughs, experts caution against viewing genetics as the sole determinant of success. Marie Spreckley, an obesity specialist from the University of Cambridge, noted that while the findings provide “plausible evidence” for genetic influence, the actual clinical impact is relatively minor. In fact, the research indicates that non-genetic variables—including biological sex, the specific type of medication prescribed, the dosage, and the length of the treatment—play a far more dominant role in determining outcomes.
Ultimately, while this study marks a pivotal step toward precision medicine in obesity care, the current evidence suggests that genetics is merely one piece of a complex puzzle. Behavioral habits and clinical factors remain the primary drivers of weight loss. For now, the data is not robust enough to justify using genetic testing as a standard tool for guiding treatment decisions in everyday clinical practice, though it opens the door for more personalized therapeutic strategies in the future.
Adam Auton, Barry Hicks, Bertram L. Koelsch, Catherine H. Weldon, James R. Ashenhurst, Jingchunzi Shi, Michael V. Holmes, Noura S. Abul-Husn, Qiaojuan Jane Su, R. Ryanne Wu, Stella Aslibekyan, Vinh Tran and Wanwan Xu authored the research. It was spearheaded by 23andMe in collaboration with various medical institutes.
Based in San Francisco, California, United States, 23andMe is a personal genomics and biotechnology company founded in 2006 by Linda Avey, Paul Cusenza and Anne Wojcicki. The company was bought in 2025 by TTAM Research Institute, a non-profit founded by Wojcicki.
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