November 8, 2010

Overweight American children, adolescents becoming fatter

Overweight American children and adolescents have become fatter over the last decade, according to researchers at the Johns Hopkins Bloomberg School of Public Health and the National Institute on Aging.

Examining adiposity shifts across sociodemographic groups over time, they found that U.S. children and adolescents had significantly increased adiposity measures such as body mass index, waist circumference and triceps skinfold thickness.

The increases in adiposity were more pronounced in some sex-ethnic groups, such as black girls. In addition, these groups gained more abdominal fat over time, which was indicated by waist size and which posed greater health risks than elevated BMI. The researchers’ results are featured in the August issue of the International Journal of Pediatric Obesity.

“Our analysis shows that the increase in adiposity among U.S. children and adolescents was unequally distributed across sociodemographic groups and across the spectrum of BMI, waist circumference and triceps skinfold thickness measures,” said Youfa Wang, senior author of the study and an associate professor in the Bloomberg School’s Department of International Health. “Heavier children and adolescents gained more adiposity, especially waist size, and these findings were most significant among children ages 6 to 11.

“Ethnic disparities in mean BMI have also increased substantially when comparing black girls with their white counterparts for all ages combined,” he said. “Solely examining the changes in the prevalence of overweight and obesity based on fixed BMI cut points could not gain such important insights regarding shifts in the obesity epidemic.”

To examine these changes over time, researchers conducted a comprehensive analysis of nationally representative survey data collected from the National Health and Nutrition Examination Survey since the late 1980s. They examined the changes in American boys and girls ages 2 to 19, as well as by ethnic groups at the population level.

“Our research suggests that U.S. young people may be at greater obesity-related risks than what was revealed by increases in BMI, as waist circumference is a better predictor of future health risks, such as for type 2 diabetes and heart disease in adults,” said May A. Beydoun, a staff scientist with the National Institute on Aging’s Intramural Research Program and a former postdoctoral fellow in the Bloomberg School’s Department of International Health. “More vigorous efforts should be made to understand the underlying causes. Moving forward, this could help guide future population-based interventions, including those focusing on the total population and those targeting vulnerable or genetically susceptible groups,” she said.

The study was written by Beydoun and Wang.

The research was supported by the National Institute of Diabetes and Digestive and Kidney Diseases and by the National Institute on Aging.