Let’s Get Physical

Between 1965 and 2000 obesity rates in the United States quadrupled, and in 2009 nearly 32 percent of American children between the ages of six and eleven were overweight. The adverse health outcomes associated with childhood obesity such as cardio-vascular disease and Type-2 diabetes cause lasting harm to children and impose significant costs on society. The American Academy of Pediatrics and Institute of Medicine blame the lack of physical activity in part for the troubling incidence of obesity and have called for school systems to mandate at least 150 minutes of physical education (PE) a week. Several states instituted PE mandates in the early 2000s, but few studies established a causal relationship between minutes spent in gym class and lower bodyweight. In “The Impact of Physical Education on Obesity Among Elementary School Children”, Cawley, Frisvold, and Meyerhoefer studied the implementation of state PE mandates to see if increasing the amount of time spent in PE class caused significant weight loss in overweight children.

The researchers used a data set of over 8,000 children from the Early Childhood Longitudinal Study whose parents and teachers were interviewed about a variety of topics between 1998 and 2004. The authors followed cohorts of children over time and studied the effect of time spent in PE classes on bodyweight. The detailed data allowed researchers to control for factors such as parents’ income or average education levels, which correlate with both lower rates of obesity and minutes spent in PE.

Concerned that children who are already in shape might voluntarily choose to spend more time in PE classes, the authors used state PE mandates to isolate the effect of PE time on BMI. Since PE mandates increase the time all children spend in PE classes, by comparing children in states with mandates and children in states without mandates, the authors are able to isolate part of the effect of PE time on children’s BMI, independent of children’s attitudes toward PE.

The researchers found by increasing PE time by 50 minutes, the probability that a child in fifth grade would be obese decreased by four percent, which was an 18 percent reduction compared to the control group’s obesity rates. Fifty minutes of additional exercise in school lowered body mass indexes by eight percent of a standard deviation from the mean BMI for children’s age range.

Although separate estimates found a statistically significant impact for boys, PE mandates had no statistically significant impact on girls’ bodyweight. The researchers speculated that boys might be taking more advantage of the rigorous aspects of gym class or that gym teachers might not push girls to participate. They suggest therefore suggested more research to investigate this discrepancy.

Some health activists expressed concern that time spent in gym class could “crowd out” other physical activities during a child’s day and make little inroads in sedentary lifestyles; however, the researchers found that additional PE was associated with statistically significant increases in weekly physical activity and structured sports, with some drop off in dance classes or playground activity.

This study is encouraging for those who believe that increased physical activity can help combat the rise of childhood obesity. While in some contexts, increasing PE time in schools might detract from time spent on academics, the authors note that, in most states with PE mandates, policymakers also increased the length of the school day to compensate for time in gym class. Moreover, in states with PE mandates, schools did not fully comply with the law. The researchers found that on average, 100 extra minutes of mandated PE would only translate to an additional 40 minutes spent in gym class each week. Extending PE mandates to other states and enforcing existing laws could provide a viable way to further improve the health of America’s children.

Feature Photo: cc/(wajakemek|rashdanothma)