Summary: While GLP-1 medications like Ozempic, Wegovy, and Zepbound have revolutionized obesity treatment, the results are famously inconsistent—some patients lose 20% of their body weight while others struggle to hit 5%.
A landmark study has identified the genetic basis for this “trial and error” reality. By analyzing nearly 28,000 individuals, researchers pinpointed specific variants in the GLP1R and GIPR genes that act as biological dials, determining both the speed of weight loss and the severity of side effects like nausea and vomiting.
Key Facts
- The “Super-Responder” Variant: A specific missense variant in the GLP1R gene (rs10305420) was linked to significantly higher weight loss—carriers lost about 0.76 kg (1.6 lbs) more per allele than non-carriers.
- Side Effect Signaling: The study identified that nausea and vomiting aren’t just “bad luck”; they are linked to variations in the very genes the drugs target.
- Tirzepatide Specificity: A variant in the GIPR gene was found to predict nausea specifically for users of tirzepatide (Mounjaro/Zepbound) but not semaglutide. This is because tirzepatide targets both GLP-1 and GIP receptors.
- Broad Spectrum of Risk: Depending on genetics and clinical factors, a patient’s chance of experiencing nausea or vomiting can range from a manageable 5% to a debilitating 78%.
- Precision Obesity Tool: 23andMe has integrated these findings into its Total Health service, allowing members to use an interactive tool to estimate their personal weight loss (6% to 20%) and side effect risk before starting treatment.
Source: 23andMe Research
GLP-1 receptor agonists, including semaglutide and tirzepatide, have transformed the clinical management of weight and obesity. However, patients experience substantial variability in both weight loss efficacy and the incidence of side effects.
Some individuals lose less than 5% of their body weight, whereas others lose more than 20%. Some individuals experience side effects such as nausea and vomiting, whereas others do not.
Published today in Nature, the study investigates the genetic basis of this variability. Researchers at 23andMe conducted a large-scale genome-wide association study (GWAS) utilizing data from 27,885 individuals who have used GLP-1 medications.
The findings provide direct evidence that variation in the genes targeted by GLP-1 medications contribute to why people respond differently to GLP-1 therapies.
“The study demonstrates the incredible power of our crowdsourced research community to advance scientific understanding of human genetic variation,” said Adam Auton, Vice President of Human Genetics at 23andMe Research Institute and an author of the study.
By analyzing both genetic markers and self-reported patient experiences, the research team uncovered several key insights into how human genetics influence the effects of these widely prescribed medications:
- Weight Loss: Researchers identified a missense variant, a small change in a gene sequence that alters the protein it makes, in the GLP1R gene that is significantly associated with increased efficacy of GLP-1 medications.
- Nausea and Vomiting: The study identified associations linking variation in both the GLP1R and GIPR genes to GLP-1 medication-related nausea or vomiting.
- Drug-Specific Effects: The association between the GIPR genetic variation and nausea and vomiting side effects is restricted specifically to individuals using tirzepatide (Mounjaro© and Zepbound©), and not semaglutide (Ozempic© and Wegovy©).
These discoveries lay the foundation for more personalized approaches in the treatment of obesity, suggesting a future where genetic testing could help guide treatment strategies.
The 23andMe research team successfully incorporated these findings into a broader model of GLP-1 medication response that includes demographic and clinical factors, demonstrating the ability to stratify patients by both weight loss efficacy and risk for certain side effects.
The organization has released a new report, called GLP-1 Medications Weight Loss and Nausea, to members of its Total Health service. The new report provides insight into weight loss and nausea risk when taking a GLP-1 medication based on these new findings from 23andMe research.
This new report includes an interactive tool that allows individuals to explore how genetics and other factors like age and certain medical conditions may impact weight loss and nausea on GLP-1 medications. Together, these factors can predict significant variability in an individual’s likelihood of weight loss or side effects.
Among 23andMe research participants, weight loss estimates vary between 6% and 20% of starting weight, and the chances of nausea or vomiting range from 5% to 78%, depending on genetics and other factors.
The new GLP-1 Medications: Weight Loss and Nausea report is exclusively available through 23andMe’s Total Health service, which includes clinician guidance. Total Health Reports are reviewed by clinicians and intended for use in a supervised clinical context.
“While there is high interest in GLP-1 medications, there is significant variation in how well they work for different people. The market is crowded with weight loss support and medications, but the approach to weight management is typically one of trial and error. This can lead people to leap into treatment with a high degree of uncertainty and unrealistic expectations about efficacy and possible side effects, said Dr. Noura Abul-Husn, MD, PhD, Chief Medical Officer at the 23andMe Research Institute.
“We believe these reports are a step forward in meeting an unmet need for a more informed and personalized approach to weight management.”
“The new GLP-1 report is a part of our Total Health service, where a clinician is part of the conversation,” continued Abul-Husn.
“GLP-1 treatment decisions are complex and having access to clinical expertise to help contextualize your genetic results alongside your full health picture is exactly the kind of guidance this report is designed to support.”
Key Questions Answered:
A: Not exactly. While the GLP1R variant increases your “efficiency,” genetics is only one part of the puzzle. Factors like your starting weight, age, diet, and drug dose still play the dominant role. Think of the gene as a “tailwind”—it makes the journey easier, but you still have to steer the ship.
A: Semaglutide (Ozempic/Wegovy) is a “monotherapy” that only targets the GLP-1 receptor. Tirzepatide (Zepbound/Mounjaro) is a “dual-agonist” that targets both GLP-1 and GIP. Because it’s hitting that second target, variations in the GIP receptor gene directly impact how the body reacts to that specific drug.
A: It can’t make a “yes/no” decision, but it can provide a “heads up.” If your genetics put you in the 78% risk category for vomiting, you and your doctor might choose to start at an ultra-low dose or prioritize a different weight-management strategy to avoid a miserable experience.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this genetics and weight loss research news
Author: Catherine Afarian
Source: 23andMe Research
Contact: Catherine Afarian – 23andMe Research
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Genetic predictors of GLP1 receptor agonist weight loss and side effects” by Qiaojuan Jane Su, James R. Ashenhurst, Wanwan Xu, Vinh Tran, R. Ryanne Wu, Catherine H. Weldon, Jingchunzi Shi, Barry Hicks, 23andMe Research Team, Noura S. Abul-Husn, Stella Aslibekyan, Michael V. Holmes, Bertram L. Koelsch & Adam Auton. Nature
DOI:10.1038/s41586-026-10330-z
Abstract
Genetic predictors of GLP1 receptor agonist weight loss and side effects
The development of glucagon-like peptide 1 (GLP1) receptor agonists, including semaglutide and tirzepatide, has transformed the clinical management of overweight and obesity. However, substantial inter-person variability exists in both weight loss efficacy and the incidence of side effects.
To investigate the genetic basis of this variability, here we conduct a genome-wide association study of self-reported weight loss and treatment-related side effects in 27,885 people following GLP1 receptor agonist therapy.
We identify a missense variant in GLP1R that is associated significantly with increased efficacy of GLP1 medications (P = 2.9 × 10−10), with an additional −0.76 kg of weight loss expected per copy of the effect allele.
Furthermore, we identify associations linking variation in both GLP1R and GIPR to GLP1 medication-related nausea or vomiting, with the GIPR association being restricted to people using tirzepatide.
We incorporate these findings into a broader model of GLP1 medication response, and demonstrate the ability to stratify patients by efficacy and side effect risk.
These findings provide direct genetic evidence that variation in the drug target genes contributes to inter-person variability in response and lay the foundation for precision medicine approaches in the treatment of obesity.
