New Genetic Study Identifies Why Some GLP-1 Users Lose More Weight and Face Higher Side Effect Risks

New 23andMe study in Nature identifies genetic variants in GLP1R and GIPR that predict weight loss efficacy and nausea risk for GLP-1 drug users.

By: AXL Media

Published: Apr 10, 2026, 4:03 AM EDT

Source: Information for this report was sourced from Nature

The Biological Basis of Incretin Variability

While the introduction of GLP-1 receptor agonists like semaglutide and tirzepatide has revolutionized obesity treatment, clinical outcomes remain highly unpredictable between individuals. On average, patients achieve a 10.2% reduction in body weight, yet a significant portion fails to lose even 5%, while others exceed 25% weight loss. Researchers at 23andMe and their collaborators sought to determine if inherited genetic factors could explain this spectrum of success. By conducting a massive genetic survey, the team identified that specific mutations in the very receptors these drugs target directly dictate how well the medication "sticks" and how the body reacts to the hormonal mimicry.

Identifying the "Weight Loss Allele" on Chromosome 6

The study identified a robust genetic signal at the GLP1R locus on chromosome 6, specifically a missense variant known as p.Pro7Leu. Each copy of this effect allele was found to confer an additional 0.641% reduction in Body Mass Index (BMI), which translated to roughly 0.76 kg of additional weight loss in the sample cohort. Interestingly, the frequency of this variant varies significantly by ancestry; it is found in 40% of individuals of European descent but only 7% of those with African ancestry. This discovery provides a biological explanation for why certain demographic groups may experience different baseline efficacy rates when starting incretin therapy.

The Genetic Link Between Efficacy and Nausea

For many patients, the benefits of GLP-1 drugs are hampered by severe gastrointestinal side effects, including nausea and vomiting. The GWAS data suggests these side effects are not merely accidental but are genetically linked to the drug's efficacy. Co-localization analysis revealed that the same genetic signals driving weight loss are also responsible for increased susceptibility to nausea. This implies a biological "trade-off" where the variant that makes the GLP-1 receptor more sensitive to the drug—leading to more weight loss—also makes the brain’s nausea centers more responsive, suggesting that for some, the most effective dose may also be the most difficult to tolerate.