Why Some People Lose More Weight Than Others on GLP-1 Medications: The Role of Genetics
Glucagon-like peptide 1 (GLP-1) receptor agonists, including popular medications like semaglutide (Wegovy, Ozempic) and tirzepatide (Zepbound, Mounjaro), have fundamentally changed how we treat overweight and obesity. However, the experience isn’t universal. While many see dramatic results, nearly one in four people don’t respond to the treatment, losing little to no weight.
New research suggests that the secret to this variability may be written in our DNA. A large-scale study has identified specific genetic variants that can predict both how much weight a patient will lose and whether they will experience common side effects like nausea.
The Genetic Link to Weight Loss Efficacy
A genome-wide association study involving 27,885 people found that variations in the GLP1R gene—which encodes the receptor these drugs target to increase feelings of fullness—play a significant role in treatment success. Specifically, researchers identified a missense variant known as rs10305420 that is associated with increased efficacy.
The impact of this variant is cumulative:
- One copy of the variant: Patients lost an average of about 1.7 pounds more than those without it.
- Two copies of the variant: Patients lost more than three pounds more than those without any copies.
According to a study published in Nature, each copy of the effect allele is expected to result in an additional -0.76 kg of weight loss.
Understanding Side Effects and Medication Response
Beyond weight loss, genetics also influence how patients tolerate these medications. The research identified associations between variations in both the GLP1R and GIPR genes and the incidence of nausea or vomiting.
Interestingly, the association with the GIPR gene was restricted specifically to people using tirzepatide. This distinction is biologically significant because tirzepatide is a dual agonist, targeting both the GLP-1 and GIP receptors, whereas semaglutide targets only the GLP-1 receptor.
The Path Toward Precision Medicine
These findings move the medical community closer to a “precision medicine” approach for obesity. Rather than a one-size-fits-all prescription, doctors may eventually use genetic stratification to:
- Predict which patients are most likely to achieve significant weight loss.
- Identify those at a higher risk for gastrointestinal side effects.
- Determine the most effective medication (e.g., a GLP-1 agonist vs. A dual GLP-1/GIP agonist) based on a patient’s genetic profile.
- Genetic Variability: Variation in drug target genes contributes to why some people lose more weight than others.
- The GLP1R Gene: The rs10305420 variant is linked to significantly higher weight loss efficacy.
- Side Effect Predictors: Variants in GLP1R and GIPR can predict nausea, with GIPR specifically impacting tirzepatide users.
- Clinical Impact: This research lays the foundation for using genetic data to personalize obesity treatment.
Frequently Asked Questions
Does this mean GLP-1 drugs won’t work if I don’t have the variant?
No. While these genetic variants explain some of the variability in weight loss, they cannot fully explain why some people lose more weight than others. Many people without these specific variants still experience significant weight loss.
Can I obtain tested for these variants now?
While the research (conducted in part by the 23andMe Research Institute) identifies these markers, they are currently used for research to understand drug response. You should consult your healthcare provider regarding the clinical availability of pharmacogenomic testing.
Why do some people experience more nausea than others?
Nausea is a common side effect of GLP-1 medications. The research indicates that genetic variations in the receptors the drugs activate (GLP1R and GIPR) can make some individuals more susceptible to these gastrointestinal issues.
As our understanding of the pharmacogenomics of obesity grows, the transition from general prescribing to personalized, genetically-informed care will likely improve both the efficacy and the safety of weight management therapies.