More gym time for kids, less obesity
The prevalence of obese elementary school kids quadrupled from 1965 to 2000, and in 2009-10, a third of children ages 6 to 11 were overweight.
More physical education in kindergarten through fifth grade means less chance of obesity, especially for boys, said researchers writing in the Journal of Health Economics. Their study provides some of the first evidence of a causal effect between a lack of gym time and childhood obesity.
A number of health organizations, including the Centers for Disease Control and Prevention, have advocated for more gym time as one response to the dramatic rise in childhood overweight and obesity. But there has not been much known about the effect of such classes, the researchers said.
They took information from a national registry, the Early Childhood Longitudinal Study, and from states that require minutes spent in physical education to determine the effects. More gym time reduces the probability of obesity among fifth-graders — more so among boys than girls, the study found. And it found that the rise in gym time did not replace academic time or harm test scores.
So what's the result? An additional hour of gym time lowers the body mass index (BMI) by 0.5 for all children, but 0.9 for boys. (BMI is a measure based on height and weight. A score over 25 indicates that a person is overweight.) Put another way, those extra 60 minutes reduce the probability that a fifth-grader is obese by 4.8 percentage points.
The researchers found that the additional physical education time has a negligible effect for girls. One explanation is that gym complements boys' participation in organized sports and other structured activity, but for girls gym is a substitute for those other activities, said lead researcher John Cawley, a Cornell University professor of policy analysis and management.
Overall, that compares with other comprehensive interventions of diet and activity that resulted in a reduction of 1.9 to 3.3 BMI units after a year.
The researchers measured children who went to kindergarten in fall 1998. Data were collected about them at several points through fifth grade, including gender, height and weight, as well as measures of their activity in and out of school and time watching TV.
The surgeon general urged all school systems to require 150 minutes per week of physical education; as of 2006, only 3.8 percent of elementary schools had done so.
Los Angeles Times