Table 1 Participants characteristics according to chronotypes (morningness-eveningness questionnaire score) (n = 952)

Age (years, means ± SD)

10.20 ± 0.40

10.21 ± 0.41

10.18 ± 0.38

0.034

Sex (girls, %)

48.42

50.30

44.06

0.077

Anthropometric variables:

Body mass index (kg/m², means ± SD)

Overweight (%)

17.43 ± 3.31

17.75%

17.21 ± 3.22

15.17

17.94 ± 3.46

23.78

0.002

0.001

Parental marital status (married, %)

90.23

90.54

89.51

0.624

Parental education level on college (%)

0.678

Both had a college degree

39.39

43.84

45.10

Only one of them had a college degree

16.39

15.92

17.48

None of them had a college degree

44.22

40.24

37.41

Meal time (h:min, means ± SD)

Breakfast time weekdays

7:01 ± 17

6:59 ± 16

7: 03 ± 19

0.012

Breakfast time weekends

8:07 ± 39

8: 03 ± 39

8:18 ± 39

< 0.0001

Lunch time weekday

11:35 ± 22

11: 34 ± 21

11:39 ± 24

0.003

Lunch time weekends

11:40 ± 30

11: 44 ± 36

11:49 ± 34

< 0.0001

Dinner time weekday

17:57 ± 31

17:56 ± 30

17:59 ± 33

0.097

Dinner time weekends

17:56 ± 33

17:54 ± 33

18:00 ± 34

0.013

Weekdays Eating midpoint

13:02 ± 35

12:58 ± 34

13:10 ± 38

< 0.0001

Weekends Eating midpoint

7:43 ± 44

13:37 ± 45

13:56 ± 45

< 0.0001

Eating jet lag (h, means ± SD)

0.73 ± 0.47

0.69 ± 0.47

0.82 ± 0.45

< 0.0001

Breakfast skipping ( ≦ 6 days/ week, %)

6.51

6.01

7.69

0.334

Eating behaviors (%)

Green vegetables intake( ≧ 1 times /week)

72.90

74.17

69.93

0.177

Fruit intake ( ≧ 1 times/day)

74.68

76.43

70.63

0.059

Milk intake ( ≧ 1 times/day)

57.98

60.36

52.45

0.023

Sugary drinks ( ≧ 1 days/week)

44.43

42.19

49.65

0.034

Fast food ( ≧ 1 days/week)

30.57

27.18

38.46

0.001

Physical activity (days/week, means ± SD)

Light physical activity 60 min a day

2.96 ± 2.17

3.12 ± 2.22

2.61 ± 2.04

0.001

Moderate physical activity 60 min a day

2.28 ± 1.97

2.42 ± 2.04

1.96 ± 1.78

0.001

Muscle strengthening activity 60 min a day

2.66 ± 2.31

2.84 ± 2.38

2.22 ± 2.06

0.001

Circadian parameters (h:min, means ± SD)

Bedtime weekdays

21:20 ± 33

21:16 ± 33

21:30 ± 33

< 0.0001

Wake time weekdays

6:41 ± 18

6:40 ± 18

6:44 ± 18

< 0.0001

Bedtime weekends

21:40 ± 38

21:34 ± 38

21:53 ± 34

< 0.0001

Wake time weekends

7:43 ± 44

7:37 ± 41

7:58 ± 46

< 0.0001

Average sleep duration (h/night, means ± SD)

9.26 ± 0.53

9.32 ± 0.38

9.13 ± 0.46

< 0.0001

Sleep duration in weekdays (h/night, means ± SD)

9.35 ± 0.55

9.40 ± 0.54

9.24 ± 0.56

< 0.0001

Sleep duration in weekends (h/night, means ± SD)

9.03 ± 0.63

9.10 ± 0.62

8.86 ± 0.60

< 0.0001

Social jetlag (h, means ± SD)

0.40 ± 0.35

0.38 ± 0.35

0.46 ± 0.34

< 0.0001