Table 1 Participant characteristics (Data are median (IQR) unless stated otherwise)

Gender, n (%)

738

411 (55.7)

327 (44.3)

Age, y, mean (SD)

14.5 (0.5)

14.5 (0.5)

14.5 (0.5)

0.19

BMI, mean (SD)

20.6 (3.3)

20.9 (3.2)

20.3 (3.2)

<0.01

Ethnicity, % White

94.9

94.2

95.7

0.34

SEP, %

0.53

  Low

13.4

12.2

15.0

  Middle

22.8

23.3

22.0

  High

63.8

64.5

63.0

Family functioning

0.00 (−0.68, 0.51)

−0.03 (−0.75, 0.62)

0.01 (−0.61, 0.45)

0.97

Friendship quality

  Good qualities

0.03 (−0.67, 0.57)

0.02 (−0.7, 0.59)

0.03 (−0.58, 0.53)

0.60

  Difficulties

−0.04 (−0.49, 0.61)

−0.05 (−0.44, 0.55)

−0.02 (−0.55, 0.65)

0.88

MVPA, min/d

  Weekday

56.9 (28.8, 98.4)

43.0 (20.7, 72.5)

79.1 (44.0, 122.6)

<0.01

  Weekend

39.4 (12.0, 85.0)

28.4 (7.2, 61.5)

60.8 (19.7, 114.5)

<0.01

Sedentary time, hours/d

  Weekday

5.7 (4.1, 7.7)

6.7 (4.7, 8.3)

4.7 (3.6, 6.5)

<0.01

  Weekend

6.3 (4.7, 8.2)

6.3 (4.8, 8.5)

6.3 (4.6, 8.1)

0.14

TV viewing, min/d

  Weekday

90 (60, 150)

90 (60, 150)

120 (60, 150)

0.76

  Weekend

120 (90, 180)

120 (75, 180)

120 (90, 180)

0.76

Internet use, min/d

  Weekday

60 (30, 120)

90 (45, 120)

60 (30, 120)

<0.01

  Weekend

90 (60, 180)

120 (60, 180)

60 (30, 120)

<0.01

Video games, min/d

  Weekday

0 (0, 30)

0 (0, 0)

45 (10, 90)

<0.01

  Weekend

0 (0, 60)

0 (0, 0)

60 (30, 120)

<0.01

Homework, min/d

  Weekday

60 (30, 90)

60 (50, 105)

60 (30, 60)

<0.01

  Weekend

60 (30, 120)

60 (40, 120)

60 (30, 90)

<0.01

Reading, min/d

  Weekday

20 (0, 30)

30 (0, 45)

10 (0, 30)

<0.01

  Weekend

20 (0, 60)

30 (0, 60)

5 (0, 60)

<0.01