Weight-loss medications have reshaped how obesity is managed, offering real results for many patients. Yet the outcomes vary widely. Some individuals lose less than 5% of their body weight, while others see reductions exceeding 20%. A recent study sheds light on this gap, pointing to genetics as a key factor behind these different responses.
Medications such as Ozempic, Mounjaro, and Zepbound belong to a group called GLP-1 receptor agonists. These drugs mimic a naturally occurring hormone in the body that helps regulate appetite and blood sugar levels. By slowing digestion and increasing the feeling of fullness, they support reduced calorie intake over time.
This mechanism has made them widely used in weight management. However, the results are not consistent across all users, raising questions about what drives these differences.
Study Highlights the Role of Genetics
Research conducted by the 23andMe Research Institute and published in the journal “Nature” explored how genetic variation may influence the effectiveness of these medications. The study examined genetic markers alongside patient-reported experiences with GLP-1 drugs.
The dataset included nearly 28,000 participants who had used at least one of these medications, with a median treatment duration of 8.3 months. This large sample provided a detailed look at how individuals respond over time.
Researchers identified specific genetic variants that appear to impact both effectiveness and side effects.
Key Genetic Findings from the Research
One notable discovery involved a variant in the GLP1R gene. Individuals carrying a single copy of the variant known as rs10305420 lost an average of 0.76 kilograms more over approximately eight months compared to those without it.
Another finding focused on a variant in the Gastric Inhibitory Polypeptide Receptor (GIPR). This variation was linked to side effects such as nausea and vomiting in patients taking medications like tirzepatide, including Mounjaro and Zepbound. Interestingly, this variant did not influence the amount of weight lost.
These findings suggest that genetics may shape both how well the drugs work and how the body tolerates them.
Experts Weigh In on the Findings
Noura Abul-Husn, chief medical officer at the 23andMe Research Institute, pointed out a common challenge in current treatment approaches. Weight management often relies on trial and error, which can lead to uncertainty and unrealistic expectations about results and side effects.
Marie Spreckley, research program manager at the University of Cambridge, who was not involved in the study, described the results as biologically plausible. She noted that genetic differences likely contribute to varied responses, though their overall clinical impact appears limited.
Typical weight loss in clinical trials ranges from 10% to 15%. In comparison, a difference of less than one kilogram per genetic variant remains relatively small.
Cristóbal Morales, head of the metabolic health, diabetes, and obesity unit at Vithas Hospital in Seville and a member of the Spanish Society for the Study of Obesity, emphasized the future potential of these findings. He highlighted pharmacogenomics—the study of how genes affect drug response—as an important step toward more precise treatment strategies.
Other Factors That Matter
While genetics play a role, they are only part of the picture. Factors such as sex, type of medication, dosage, and duration of treatment appear to explain a larger share of the differences in outcomes.
This means two individuals with similar genetic profiles may still experience different results based on how the treatment is administered and how their bodies respond over time.
The findings point toward more personalized strategies in obesity care, where treatment plans can be adjusted based on how individuals are likely to respond and their risk of side effects. This approach could improve accuracy in prescribing these medications.
At the same time, experts note that genetic insights alone are not enough for routine clinical use. Additional research is still required to validate these findings and integrate them into everyday treatment decisions.
While weight-loss drugs continue to play a major role in managing obesity, results vary due to a mix of genetic and clinical factors. Understanding these differences may support more precise and effective treatment outcomes over time.
