Journal of Obesity & Metabolic Syndrome



Korean J Obes 2008; 17(4): 169-174

Published online December 1, 2008

Copyright © Korean Society for the Study of Obesity.

The cut off value of body fat percentage for diagnosing obesity among selected number of elementary school students in Seoul

In Cheol Hwang, Kyoung Kon Kim*, Dong Hoon Suh(1), Kyu Rae Lee

Department of Family Medicine, Gachon University Gil Medical Center; and
Department of Family Medicine, Dong Sin General Hospital*


Background: Measurement of body fat amount is
necessary in assessment of obese people. Bioelectric
impedance analysis (BIA) is an indirect method of
measuring body fat amount, which has been widely
applied in clinical and field settings because of its
relatively low cost and non-invasive character. We tried to
define the cut off values of body fat amount measured by
BIA method which would correspond to those of body
mass index (BMI) in order to detect overweight and
obesity in children of this trial.
Methods: By using the BIA method, measurements of
height, weight and body fat percentage of 1321
sixth-grade students (aged 10~12 years) were taken from
eight different elementary schools located in
Seodaemun-gu, Seoul, Korea. The student’s BMI
percentiles for their age and gender were determined
based on the Korean pediatrics society growth chart
established in 2007, then they were categorized into three
groups; normal, overweight and obese. The cut off values
of body fat percentage, which would correspond to those
of BMI percentiles were calculated by ROC curve
Results: Among 1286 subjects, 35 were excluded due
to mechanical malfunction. The mean body fat percentage
was 18.5 ± 2.1% in normal group, 23.6 ± 1.1% in
overweight group and 27.2 ± 2.1% in obese group. For
classification of overweight, the correspondent cut off
value of body fat percentage was 29% in boys and 26%
in girls. For obesity, the cut off value was 31% for both
boys and girls. The kappa values for the agreement
between BMI percentiles criteria and body fat percentage
cut off values were 0.5974 in boys and 0.6056 in girls (P
< 0.001).
Conclusion: According to the criteria suggested by the
Korean pediatrics society in 2007, the most appropriate
cut off values of body fat percentage in 10~12 years old
children were 29% for overweight and 31% for obesity in
boys, and 26% for overweight and 31% for obesity in
girls, respectively.

Keywords: percentage body fat, body mass index, bioelectric impedance analysis, cut off value