Table 1. Prevalence of obesity according to selected socioeconomic and demographic characteristics, by sex.

	Male			Female
	No. of Subjects	Obesity (%)	SE	No. of Subjects	Obesity (%)	SE
Total	31 632	12.8	0.2	29 011	5.5	0.2
Grade level
7	5835	7.4	0.4	4989	5.8	0.3
8	5485	10.7	0.4	5034	7.5	0.3
9	5334	12.7	0.6	5175	9.2	0.4
10	5318	13.8	0.6	5133	9.6	0.4
11	4933	16.2	0.6	4440	12.2	0.5
12	4727	17.6	0.6	4240	12.9	0.5
Paternal education
Middle school ​ or less	2476	15.5	0.9	2283	8.4	0.7
High school	12 667	13.8	0.4	12 568	6.1	0.3
College or higher	12 011	11.8	0.4	11 287	4.5	0.2
Unknown	4478	11.9	0.5	2873	5.7	0.6
Maternal education
Middle school ​ or less	2702	16.0	0.8	2705	9.1	0.7
High school	15 847	13.4	0.3	16 351	5.4	0.2
College or higher	8071	11.6	0.5	7145	4.8	0.3
Unknown	5012	11.5	0.6	2810	5.5	0.6
Family affluence scale
Low	9727	10.1	0.3	9101	6.5	0.3
Middle	14 731	9.4	0.3	13 693	5.4	0.2
High	7174	8.4	0.3	6217	4.5	0.2
Subjective family economic status
Low	1410	16.6	1.1	1236	11.0	1.1
Low-middle	5158	14.2	0.5	5444	7.1	0.5
Middle	15 105	12.4	0.3	14 764	5.2	0.2
High-middle	7857	12.8	0.5	6255	4.4	0.3
High	2102	10.4	0.8	1312	4.7	0.6
Subjective school achievement
Low	3424	15.3	0.7	2832	8.2	0.7
Low-middle	7448	13.9	0.5	7224	6.7	0.4
Middle	8632	12.3	0.5	7904	4.9	0.3
High-middle	8106	12.5	0.5	7627	5.2	0.3
High	4022	10.3	0.5	3424	3.2	0.3

SE: standard error. To reflect the stratified cluster sampling design of the 2007 Korea Youth Risk Behavior Web-based Survey, obesity prevalence was calculated by using the “survey frequency procedure” of SAS version 9.1.