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 10^thpercentile, 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 97^thpercentiles of BMI for girls, this rising trend seems to stop. Boys generally have higher BMIs than girls. The exceptions are younger ages of 90^thand 97^thpercentiles and older ages of 3^rdand 10^thpercentiles. 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.