Table 1. Characteristics of participants by sex.

Total n = 7,998		Boys % n = 4,157	Girls % n = 3,841	P value
Skipping breakfast	yes	6.9	6.9	0.960
Physical activity	very often	31.2	24.7	<0.001
	often	46.3	51.5
	rarely	22.6	23.7
TV viewing, hours on weekdays				<0.001
	<2	66.5	59.7
	2 to <3	23.2	28.0
	≥3	10.3	12.4
Sleep duration, less than 8 hours		5.4	6.2	0.122
Food frequency (except school lunch)
Fruit	almost every day	34.5	39.1	<0.001
	3 to 5 times per week	36.2	37.3
	0 to 2 times per week	29.3	23.7
Vegetables	almost every day	61.0	63.8	0.001
	3 to 5 times per week	26.1	25.8
	0 to 2 times per week	12.9	10.4
Overweight		16.1	13.5	0.001
Psychological stress, family environment
irritability	often	14.3	15.0	0.520
	sometimes	54.5	54.6
	rarely	31.2	30.3
unwillingness to attend school	often	8.0	6.5	0.025
	sometimes	29.2	30.8
	rarely	62.9	62.6
interaction with parents	often	21.9	31.1	<0.001
	sometimes	42.7	41.7
	rarely	35.5	27.1
mother’s employment	full-time	38.4	40.2	0.029
	part-time	30.6	30.1
	unemployed	31.0	29.7
dinner	with both parents	55.4	54.9	0.795
	with either parent	38.5	38.6
	without parent	6.1	6.5
Bowel movement	daily or more	78.3	69.0	<0.001
	once every 2 days	19.0	26.1
	less frequently	2.8	5.1

Pearson chi-square test.