Background: Being overweight in adolescence is the strongest predictor of becoming overweight in adulthood; 85 percent of adolescents who are obese become obese in adulthood. No specific intervention has been proven to reduce this likelihood. Increased physical activity, such as daily physical education (PE), has been associated with lower body weight; however, the number of high schools requiring PE has declined. Among U.S. high schools, only 13.3 and 5.4 percent require PE for freshmen and seniors, respectively, and 44 percent of high school students are not enrolled in PE. Extracurricular physical activity may also protect against overweight during adolescence, but no study has examined the relationship between school-associated and extracurricular physical activities and the potential effect on subsequent adult weight. Menschik and colleagues examined how increased physical activity (curricular and extracurricular) in adolescence affected weight in adulthood.

The Study: The authors surveyed adolescents in seventh through 12th grades about the number of times in the previous week they had participated in PE or extracurricular physical activity; there were no survey data on duration, intensity, or location of exercise. Extracurricular activities were grouped into three types: rollerblading, roller-skating, skateboarding, and bicycling (type 1); baseball, softball, basketball, soccer, swimming, and football (type 2); and jogging, walking, karate, jumping rope, gymnastics, and dancing (type 3). Body mass index (BMI) was calculated based on self-reported anthropometric data. Respondents were surveyed again five years later, with an age range of 18 to 26 years. A BMI of 25 kg per m2 or greater was considered overweight. Respondents were excluded if they were pregnant, had a physical disability, or had extreme morbid obesity.

Results: Initially and at the five-year follow-up, 3,345 adolescents were surveyed. The percentage of respondents who were overweight increased from 28.1 percent initially to 50.6 percent at the five-year follow-up. Of the 941 adolescents who were overweight, only 10.9 percent transitioned to a normal weight as adults, whereas 35.6 percent of normal-weight adolescents became overweight in adulthood. Adolescents who engaged in type 1 activities more than four times per week or type 2 activities three to four times per week were significantly less likely to become overweight after five years (odds ratios [OR] = 0.52 and 0.80, respectively). Those who participated in these activities less often and those engaging in type 3 activities showed no decrease in likelihood of becoming overweight. The authors noted that type 3 activities may specifically select for adolescents with increased muscle mass, which may lead to overweight misclassifications.

School-based PE was also associated with a reduced likelihood of becoming overweight. Each day that normal-weight adolescents participated in PE reduced the chance of becoming overweight by 5 percent, with the greatest effect occurring in those participating in PE five days a week (OR = 0.75). However, this protective effect did not occur in adolescents who were initially overweight.

Conclusion: Evidence from this study indicates that engaging in extracurricular or school-based physical activities may be a factor in preventing adulthood overweight. This protective effect seems to occur in normal-weight adolescents; therefore, the authors suggest an emphasis on prevention rather than intervention. These results may have implications for policy makers who make funding decisions for adolescent physical activity programs both in and out of schools.