Obesity is twice as common in young American Indian/Native Alaskan children as it is in white and Asian children, according to new research offering the first nationally representative analysis of obesity prevalence among preschool-aged kids in five major racial/ethnic groups.
The analysis also shows that obesity prevalence is higher in Hispanic and black children than it is in whites and Asians.
The research offers evidence that obesity prevalence differs among racial and ethnic groups in the United States in children as young as age 4. This is the first study to include national estimates of obesity prevalence among preschool children who are American Indian/Native Alaskan and Asian.
Overall, an estimated 18.4 percent of 4-year-olds in the United States are considered obese based on measures of their weight relative to their height, according to the study.
The data indicated there are three tiers of obesity prevalence among young children of different racial and ethnic backgrounds. Based on body mass index measures, obesity prevalence was estimated at 31.2 percent among American Indian/Native Alaskan children, 22 percent for Hispanics, 20.8 percent in blacks, 15.9 percent of whites and 12.8 percent in Asians.
"The implications are that childhood obesity prevention efforts must begin early in life. And these efforts might benefit from better understanding of how differences in obesity risk between racial and ethnic groups emerge so early," said Sarah Anderson, assistant professor of epidemiology at Ohio State University and lead author of the study.
Anderson conducted the analysis with Robert Whitaker of Temple University. The research is published in the April issue of Archives of Pediatrics & Adolescent Medicine .
Anderson and Whitaker analyzed height and weight data collected in 2005 on 8,550 children who were born in the United States in 2001. The data were collected as part of the Early Childhood Longitudinal Study, Birth Cohort, which is an ongoing study conducted by the National Center for Education Statistics to provide information about learning environments, health and development of young U.S. children.
The researchers calculated the body mass index (BMI) of the children using the measured heights and weights of the children. BMI is derived by dividing weight in kilograms by height in meters squared.
BMI measures for adults use set numbers to define overweight or obesity, but those numbers do not apply in growing children whose bodies are constantly changing, Anderson explained. In this study of preschool children, BMI measures were converted into percentiles for age and sex based on growth charts developed by the Centers for Disease Control and Prevention in 2000.
Children whose BMI scores were at or above the 95th percentile on those charts were referred to as obese for the purposes of this analysis. Because obesity rates based on BMI have been increasing steadily for adults and children in the United States over the years, a total of 18.4 percent of the 4-year-olds studied now rank in what used to represent just the top 5 percent of BMI scores among children of the same age.
The children's race and ethnicity were defined in part by what their mothers chose using categories established for the U.S. census. The researchers placed each child in one of five mutually exclusive categories: American Indian/Native Alaskan, Hispanic, non-Hispanic black, Asian and non-Hispanic white.