comparing the body mass index and fat mass index to identify overweight in children

background: the sensitivity and specificity of body mass index (bmi) percentiles of centers for disease control 2000 (cdc2000) standard was compared with child actual overweight which was identified by fat mass index (fmi) and overweight status in these children based on bmi and fmi. methods: in this case-control study, elementary school girls (aged 8-10 years) were recruited from schools of isfahan, iran. weight, height and fat mass were measured by body composition analyzer (bca) and by calculating bmi (weight in kilogram divided by height in meters squared) and fmi (fat mass in kilogram divided by height in meters squared) and then the bmi and fmi were compared. bmi ≥ 95 th and bmi < 95 th percentile of the cdc2000 standards were used for overweight and non-overweight definition, respectively. fmi on or above the 90 th percentile and fmi < 90 th percentile based on the reference data were considered as criteria for actual overweight and actual non-overweight, respectively. findings: mean (± standard deviation) of fmi and bmi in all children were 6 ± 2.1 and 19.4 ± 3, respectively. the sensitivity and specificity of 95 th percentile of bmi to identify children as overweight in comparison with fmi were 57.3% and 98.4%, respectively. 1.6% of the children, who were identified as non-overweight based on fmi, were overweight based bmi, and 57.3 % of the children who were overweight based on fmi, were also overweight based on bmi. conclusion: it appears that fmi in comparison with bmi has more ability to determine overweight; however, further studies are required in this field.