New Genetic Study Identifies Why GLP-1 Weight Loss Efficacy and Side Effects Vary Between Patients

A new 23andMe study identifies DNA variants that predict GLP-1 efficacy and nausea risk, enabling a more personalized approach to obesity treatment.

By: AXL Media

Published: Apr 8, 2026, 11:39 AM EDT

Source: Information for this report was sourced from EurekAlert!

Investigating the Genetic Basis of Medication Response

As GLP-1 receptor agonists like semaglutide and tirzepatide become standard in obesity management, clinicians have observed vast differences in patient outcomes. While some individuals lose over 20% of their body weight, others see minimal results or experience debilitating side effects. A new study from the 23andMe Research Institute, involving nearly 28,000 participants, provides the first direct evidence that human genetic variation in the target genes of these drugs is responsible for this inconsistency. By analyzing crowdsourced data, researchers have moved a step closer to understanding the biological blueprints that dictate drug efficacy.

Identifying Key Variants in Weight Loss Efficacy

The research team identified a specific "missense variant"—a small but impactful change in the DNA sequence—within the GLP1R gene. This variant is significantly associated with increased weight loss efficacy, explaining why some patients respond more robustly to the medication than others. According to Adam Auton, Vice President of Human Genetics at the 23andMe Research Institute, this study demonstrates the power of large-scale genetic data to uncover hidden patterns in how the body processes modern therapies, turning patient experiences into actionable scientific insights.

Decoding the Genetics of Nausea and Vomiting

Side effects such as nausea and vomiting are the most common reasons patients discontinue GLP-1 therapy. The study pinpointed associations in both the GLP1R and GIPR genes that correlate with a higher risk of these gastrointestinal issues. Interestingly, the research found drug-specific genetic effects: variations in the GIPR gene were linked to nausea and vomiting only in patients using tirzepatide, and not in those using semaglutide. This distinction suggests that genetic profiles could eventually be used to determine which specific brand of GLP-1 medication is best suited for an individual’s unique biology.