Your Genetic Risk For Obesity Reveals How Many Steps You Need To Stay Fit

NASHVILLE, Tenn. — Life is rarely fair, and new research finds that old sentiment rings especially true in the gym. Scientists from the Vanderbilt University Medical Center (VUMC) have found that people with a higher genetic risk of becoming obese really do need to exercise harder than others with a moderate or low genetic risk of gaining excess weight.

To reach this conclusion, the research team used activity, clinical, and genetic data originally gathered by the National Institutes of Health’s All of Us Research Program in an effort to explore any and all associations between the genetic risk of higher body mass index and levels of physical activity necessary to reduce obesity.

“Physical activity guidelines do not account for individual differences,” says senior author Douglas Ruderfer, PhD, associate professor of Medicine, Division of Genetic Medicine, and director of the Center for Digital Genomic Medicine at VUMC, in a media release. “Genetic background contributes to the amount of physical activity needed to mitigate obesity. The higher the genetic risk, the more steps needed per day.”

“I think an important component to this result is that individuals can be active enough to account for their genetic background, or their genetic risk for obesity, regardless of how high that risk might be,” Dr. Ruderfer adds. “And there are many other contributors that play a role including diet and environmental factors.”

The study included 3,124 middle-aged participants without obesity who owned a Fitbit device and usually walked an average of 8,326 steps daily for an average of over five years. Obesity incidence during that period increased from 13 percent to 43 percent among the lowest and highest polygenic risk score groups, respectively.

Individuals displaying a polygenic risk score in the 75^th percentile needed to walk an average of 2,280 more steps per day (a total of 11,020 steps per day) in comparison to those in the 50^th percentile in order to reach a comparable obesity risk level.

Those with a baseline BMI of 22, 24, 26, and 28 who also placed in the 75^th percentile of polygenic risk score for obesity would have to walk an additional 3,460, 4,430, 5,380, and 6,350 steps per day, respectively, to reach a comparable obesity risk level as those in the 25^th percentile.

“I think it is intuitive that individuals who have a higher genetic risk of obesity might need to have more physical activity to reduce that risk, but what is new and important from this study is that we were able to put a number on the amount of activity needed to reduce the risk,” explains lead author Evan Brittain, MD, associate professor of Medicine in the Division of Cardiovascular Medicine at VUMC and lead investigator in Digital Health for the All of Us Research Program Data and Research Center.

“It is becoming more commonplace to know you have a genetic risk for obesity in the genomic era when genetic results are being returned directly to patients. And you can imagine a future in which that data could be integrated with someone’s electronic health record and could form the basis of an individual’s physical activity recommendation from their doctor.”

Study authors note they now want to ascertain if the findings are generalizable to more representative and diverse populations. This will help determine if providing information for individual activity recommendations may result in improved health and a lower likelihood of obesity.

“We would like to test whether knowledge of one’s genetic risk for obesity actually has an impact on their behavior,” Dr. Brittain adds. “I think these findings could be empowering for patients because the current physical activity guidelines take a one-size-fits-all approach, and what we learned is that depending on your genetic risk, the guidelines may underestimate the amount of activity needed to reduce your risk of obesity.”

“Most importantly, I would like for patients to know that your genetic risk doesn’t determine your overall risk of obesity, and you can actually overcome that risk by being more active,” the doctor concludes.

The study is published in JAMA Network Open.