Body Mass Index Percentile Curves for 7 To 18 Year Old Children and Adolescents; are the Sample Populations from Tehran Nationally Representative?

Background: The children's body composition status is an important indicator of health condition evaluated through their body mass index (BMI). We aimed to provide standardized percentile curves of BMI in a population of Iranian children and adolescents. We assessed the nationally representative of sample populations from Tehran. Materials and Methods: A total sample of 14,865 children aged 7-18 years was gathered. The Lambda-Mu-Sigma method was used to derive sex-specific smoothed centiles for age via the Lambda-Mu-Sigma Chart Maker Program. Finally, the prevalence of overweight and obesity with 95% confidence interval (CI) was calculated. Results: BMI percentiles obtained from Tehran's population, except for the 10th percentile, seem to be very slightly greater than the urban boys from all over Iran. BMI percentiles have an increasing trend by age that is S-shaped with a slight slope. Only in the 90th and 97th percentiles of BMI for girls, this rising trend seems to stop. Boys generally have higher BMIs than girls. The exceptions are younger ages of 90th and 97th percentiles and older ages of 3rd and 10th percentiles. A total number of 1,008 (13.20%; 95% CI: 12.46-13.98) boys and 603 (8.34%; 95% CI: 7.72-9.00) girls were categorized as overweight and obese. Obesity were observed in 402 (5.27%; 95% CI: 4.79-5.79) boys and 274 (3.76%; 95% CI: 3.35-4.22) girls. Conclusion: We construct BMI percentile curves by age and gender for 7 to 18 years Iranian children and adolescents. It can be concluded that sample populations from Tehran are nationally representative.