Am Fam Physician. 2009 Feb 1;79(3) Online.
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.
Source: Menschik D, et al. Adolescent physical activities as predictors of young adult weight. Arch Pediatr Adolesc Med. January 2008;162(1):29-33.
EDITOR'S NOTE: A BMI of 25 kg per m2 is often accepted as the line between normal and overweight for adults; however, age, sex, and pubertal stage make this cutoff somewhat arbitrary in children. An international cross-sectional study found that children with an age-related BMI in the 80th percentile or higher at five and 10 years of age (17.4 and 19.8, respectively, for boys; and 17.2 and 19.9, respectively, for girls) was strongly associated with having a BMI greater than 25 kg per m2 by adulthood.1 This study found that physical activity is more effective at preventing overweight than reversing it.
Clearly, the emphasis should be on reducing sedentary behaviors and restricting the intake of high-calorie, low-nutrient foods. The American Academy of Pediatrics recently published guidelines for primary care-based weight management in children,2 but securing parental participation is crucial. Having parents serve as role models for lifestyle modification can effectively lead to long-term weight reduction in children.3 A parental handout is available from the U.S. Department of Agriculture Food and Nutrition Service at http://teamnutrition.usda.gov/resources/mpk_tips.pdf.-K.T.M.
1. Shephard RJ. Role of the physician in childhood obesity. Clin J Sport Med. 2004;14(3):161-168.
2. Spear BA, Barlow SE, Ervin C, et al. Recommendations for treatment of child and adolescent overweight and obesity. Pediatrics. 2007;120(suppl 4):S254-S288.
3. Epstein LH, Valoski A, Wing RR, McCurley J. Ten-year follow-up of behavioral, family-based treatment for obese children. JAMA. 1990;264(19):2519-2523.
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