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Certain genes influence people’s risk of obesity, but many aspects of their lives interact with those genes, and these interactions over a lifetime can drive people’s body mass index (BMI) further up or down. That’s according to a new study published in the International Journal of Obesity by public health researchers at the University of Hawaiʻi at Mānoa Office of Public Health Studies in the Myron. B. Thompson School of Social Work.

For the study, researchers led by Mika Thompson, a UH Mānoa public health graduate research assistant, used data from about 6,700 participants in the ongoing Health and Retirement Study, which includes samples of black and white men and women in the U.S. who are older than age 50.

Thompson and his co-authors looked at certain factors of people’s lives that they can control, such as alcohol use, smoking and physical activity, and factors that they could not control, such as the income level of their family during their childhood. In addition, saliva samples were collected from participants to test their DNA.

“Our findings reinforce the importance of physical activity among people with an elevated genetic risk for obesity,” Thompson said.

Among white women who had the highest genetic risk for obesity, the BMI of those who engaged in vigorous physical activity was 1.66 points (about 10 pounds) lower, on average, compared with those who did not engage in physical activity. The effect was less pronounced among white women with lower genetic risk.

“The association found in this study by Thompson further supports the statement that your zip code is a greater predictor of your health outcome than your genetic code,” said Lola Irvin, administrator of the Chronic Disease Prevention and Health Promotion Division in the Hawaiʻi State Department of Health, who was not involved in conducting the study. “The opportunities and choices in one’s community for physical activity, such as sidewalks, bike lanes and recreational facilities, are not determined by individual choice, but by policies and systems decisions.”

Genetic risk score

Researchers have identified thousands of genetic variations that have been linked to BMI, however, these individual variations explain only a small amount of people’s obesity risk. In the new study, the researchers took a different approach and used a calculation to create a genetic risk score based on many genetic variations that increase or decrease a person’s obesity risk. They broke down their results by race, sex and age.

Factors such as diet and exercise influence obesity risk. Moreover, research shows that these genes interact with factors in a person’s environment.

“The association between people’s genetic risk for obesity and their BMI became weaker as people aged,” said Catherine Pirkle, an associate professor with the Office of Public Health Studies and a co-author on the paper. “This suggests genetic risk for obesity becomes less influential in older adulthood.”

Other findings suggest links between BMI and alcohol consumption, and BMI and childhood socioeconomic status. The researchers will further investigate these results in future research.

Most research to date on the genes linked to obesity have come from studies of people in Europe. More research is needed to better measure genetic risk in diverse samples from the U.S. and other world regions.

“The new findings may help to improve approaches to helping people to lower their BMI during their older adulthood years,” Pirkle said.

Thompson and Pirkle’s co-authors on the paper include Office of Public Health Studies Fadi Youkhana, a graduate assistant, and Yan Yan Wu, an associate professor.

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