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^th 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 97^th percentiles of bmi for girls, this rising trend seems to stop. boys generally have higher bmis than girls. the exceptions are younger ages of 90^th and 97^th percentiles and older ages of 3^rd and 10^th 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.