Effects of physical activity on pediatric reference data for obesity.

PURPOSE: To examine the influence of physical activity on pediatric obesity reference data for Canada. METHODS: The sample included 3527 boys and 3554 girls, 6 to 18 years of age, from the 2004 Canadian Community Health Survey: Nutrition component. The heights and weights of the participants were directly measured, and the body mass index was calculated (BMI: kg/m(2)). Physical activity levels were reported using an interviewer-administered questionnaire. Participants were divided into low and high physical activity groups, based on age-specific physical activity levels (lower and upper quartiles). BMI percentiles (25th, 50th, 75th, 85th, 95th) were generated by sex using the LMS method, separately by physical activity groups. RESULTS: There were only minor differences in BMI at the 25th and 50th percentiles between physical activity groups in both boys and girls. However, in boys, the low active group had somewhat higher BMI values at the 85th and 95th percentiles than the high active group after the age of 10 years. In girls, the differences in BMI across groups was similar to that of boys at the 95th percentile, but inconsistent at the other percentiles. CONCLUSION: The results suggest that screening for physical activity may be important for the development of national reference data for obesity.