As childhood obesity has increased, many states are increasing their physical education (PE) requirements. Yet, increasing time spent in gym class does not appear to increase overall physical activity or prevent childhood obesity, according to a new Cornell study.

"Higher state PE requirements have no impact on weight or the probability of being overweight for either boys or girls," said John Cawley, an economist and associate professor of policy analysis and management at Cornell. "Higher PE requirements are associated with more days with vigorous exercise for girls, but also with fewer days with light physical activity. This may be due to girls reducing physical activity out of school when compelled to take more PE at school. The data suggest this is most common among girls who are less active in the first place. … Public health officials and educators should consider ways to reduce or eliminate such offsetting behavior."

The study, conducted with Chad Meyerhoefer of the Agency for Healthcare Research and Quality and David Newhouse of the International Monetary Fund, is published in the fall issue of the peer-reviewed journal Education Next.