One in eight children in the U.S. is obese when they enter kindergarten, with the ratio increasing through the elementary school years, a nationwide study found.
By eighth grade, 1 in 5 U.S. students is obese and another 17 percent are overweight, according to the study released Thursday by the New England Journal of Medicine. Most of the increase takes place before fifth grade, giving researchers key information about the obesity epidemic among American children and the ages at which they are most vulnerable.
Obesity more than doubled in children and tripled in adolescents from the early 1980s, though researchers say the rates may now have plateaued.
The study found that 5-year-olds carrying extra weight for their age were four times more likely to become obese during the elementary school years. Almost half of those who developed obesity were overweight when school started.
The findings suggest obesity develops mainly in children who are already overweight and tapers off over time, as the pool of susceptible students is exhausted, the researchers said.
The study was funded by the National Institute of Child Health and Human Development. The researchers analyzed data from 21,260 kindergartners enrolled in the Early Childhood Longitudinal Study in 1998. More than 9,000 were followed through the eighth grade.
It’s also not clear if similar patterns were seen among U.S. children who entered school in subsequent years, they said. In the study, a child was considered overweight if they were above the 85th percentile for weight and obese if they were above the 95th percentile as calculated by the U.S. Centers for Disease Control and Prevention.
Previous research suggests obesity develops in the U.S. at a rate of 2.5 percent a year from adolescence to adulthood.