physical education in kindergarten through fifth grade means
less chance of obesity, especially for boys, researchers say.
study provides some of the first evidence of a causal effect
between gym and childhood obesity. It is to be published in
the Journal of Health Economics.
of health organizations, including the Centers for Disease
Control and Prevention, have advocated for increased gym class
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.
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 increase in gym time did not replace academic time or
harm test scores.
the result? An additional hour of gym time lowers the body
mass index 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 overweight.) Put another way, those extra 60 minutes
reduce the probability that a fifth-grader is obese by 4.8
researchers found that the additional PE 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, says lead researcher John Cawley, a Cornell
University professor of policy analysis and management.
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 wrote.
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. The researchers, from Cornell, Emory and
Lehigh universities, measured children who went to
kindergarten in fall of 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.
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.
the five years after implementation of No Child Left Behind
law, evidence shows that 9 percent of school districts
decreased gym time.
confounding factors could include that physical fit children
are more likely to take part in gym class, and wealthier
schools may be more likely to offer it. The researchers said
they accounted for these possibilities. In addition, even in
schools with a gym mandate, there’s often poor compliance,
the researchers said.