Studies: Gym Class, Recess Reduce Likelihood of Obesity - Big gains in keeping kids active during school

September 5, 2013

Originally published June 3, 2013

It's no secret that physical activity is a key part of keeping kids healthy, but two new studies add hard evidence to what seems to be common sense: exercising in school has an important impact on students' health.

One study of kindergarteners to fifth graders across the U.S. found that physical education (PE) classes lowered body mass index (BMI) scores and reduced the probability of obesity among fifth graders. An additional hour of gym time lowered BMI for all children in the study by 0.5.

Although the U.S. Centers for Disease Control and Prevention (CDC), the American Academy of Pediatrics and other major groups have previously urged regular school PE time as a method for fighting childhood obesity, this study provides some of the first evidence of a causal link between gym classes and weight in elementary schools.

"The hope with physical education is that it influences behavior in school, but also out of school," leading to an overall more active lifestyle, said David Frisvold, Ph.D., assistant professor of economics at Emory University and one of the study's authors.

That may have been the case for the boys in the study, the authors said. The results showed that PE's effect on lowering BMI was especially true for boys, and Frisvold and his colleagues suggest that the difference is because PE is often a complement to additional physical activities, like sports teams, for boys. Girls more often use PE as a substitute for other physical activity.

The researchers studied data on schoolchildren in kindergarten through fifth grade collected by the U.S. Department of Education, including height, weight and how much time they spent each week in PE, a factor largely influenced by state laws.

States have varying regulations regarding physical education requirements for students. Some states have no PE mandate, and some states' laws require that PE be offered to students, but do not require them to enroll in it. Other states, like Georgia, mandate a specific amount of time that school children must participate in PE. Frisvold said these state laws are the ones that seemed to make the biggest difference.

"We found that state laws mattered when there were a minimum number of minutes required per week," he said. "That affected the amount of time students spent in physical education, and that in turn reduced obesity."

Georgia introduced its physical education requirement for elementary schools in 1990. The state requires that children spend 90 hours per year in PE classes, which averages out to 150 minutes per week if the PE time is evenly distributed throughout the school year. The Georgia Departments of Education and Public Health also want to increase the amount of time that kids are active through the Power Up for 30 program, which encourages all schools to add 30 additional minutes of physical activity before, during or after school.

A second study focused on another time-honored form of physical activity in schools: recess. Playworks, a national organization advocating for more recess and physical activity time in schools, released a study of its popular recess program, which focuses on increasing physical activity and nurturing leadership development on the playground. Researchers studied 29 schools who were interested in adopting the Playworks recess program for their students, randomly assigning the schools to participate in the program for two years. The results showed that schools that used the program had reduced bullying during recess, increased students' feelings of safety at school, increased the amount of vigorous physical activity during recess and provided more time for teaching and learning when kids returned to the classroom.

Playworks said the findings suggest that recess plays a more important role in creating a school's environment than simply giving kids time to blow off some steam.

"These findings tell us there is much more to recess than meets the eye," said Nancy Barrand, senior program officer for the Robert Wood Johnson Foundation, which sponsored the research trial.

Many public health and policy experts have urged schools to not turn away from PE and recess, citing their importance in combating high rates of obesity and sedentary lifestyles in children. But increased pressure to improve test scores and fit more lessons into the school day have squeezed PE and recess out of the schedule for many schools. The U.S. Surgeon General urged schools to require 150 minutes of PE each week, but as of 2006, only 3.8 percent of elementary schools did so. 

Frisvold said recognizing the importance of PE and recess is a key part of the solution to childhood obesity, but it's not the only part.

"It's important to recognize that one change or one program doesn't reduce obesity completely. We can't just say, we've tweaked the school day, so we're done," he said.

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