A new study published this week demonstrates just how powerful large-scale genetic research can be when it comes to predicting health traits—like body weight. By combining data from consented 23andMe research participants with the GIANT consortium, an international group of scientists have created the most predictive polygenic score for body mass index (BMI) to date. The study used genetic data from up to 5.1 million individuals from diverse backgrounds, helping push the science forward in important and inclusive ways.
What’s a Polygenic Score?
Think of a polygenic score (sometimes called a polygenic risk score or PRS) as a genetic summary. It adds up the small effects of many different genetic variants—often thousands or even millions—that are each linked to a trait, like BMI. The higher your score, the higher your predicted BMI. These scores are increasingly used in research, and even clinical settings, to better understand traits and potential health risks.
Why This Study Matters
One of the big takeaways from this research? The more data we include in building a polygenic score, the more accurate the predictions become. Thanks to the massive dataset, this new BMI polygenic score is one of the most accurate developed so far—and it’s also more applicable to people of diverse ancestries than previous versions.
Still, it’s important to note that while this polygenic score performs better across different populations, its accuracy is still highest in individuals of European descent. That’s because most genetic research to date has been heavily based on European-ancestry populations. Studies like this one help move the field toward more inclusive and equitable research.
What the Study Found
- Childhood weight gain: A higher BMI polygenic score was linked to faster weight gain starting from age 2.5 onwards and an earlier “adiposity rebound”—a key moment in childhood growth when BMI dips and then begins to increase again. This could help identify children at higher risk of becoming overweight before other warning signs appear.
- Adult weight change: Between ages 20 and 50, people with higher BMI polygenic scores were more likely to gain weight. Interestingly, this was especially true for those who started adulthood at a weight lower than what their genetics might predict. It suggests that individuals with a genetic predisposition to higher weight may eventually “catch up” to their genetic set point over time.
- Lifestyle changes: In lifestyle intervention studies (think: intensive diet and exercise programs), people with a higher genetic predisposition to obesity tended to lose more weight during the first year—but they were also more likely to regain it. This pattern fits with previous research showing that people who are genetically predisposed to obesity often respond more dramatically to environmental changes, both positive and negative.
What This Study Doesn’t Say
This research doesn’t mean that lifestyle doesn’t matter. In fact, it’s just the opposite. Even with a high genetic predisposition to obesity, lifestyle choices—like diet, physical activity, sleep, and stress management—still have a meaningful impact. What polygenic scores offer is insight into who may be at higher risk and might benefit most from early interventions or targeted prevention strategies.
Final Thoughts
Your genes are only one part of the story. While this research gives us a clearer picture of how genetics influence weight over time, it also highlights the importance of using that information wisely. At 23andMe, we believe that understanding your genetics can empower you to make informed health decisions—not define your destiny. As science continues to evolve, so do the tools we have to support healthier, more personalized approaches to wellness.
