Table 1

Questionnaire items, their origin, and reliability and validity (intraclass correlation)37–39

Questionnaire itemQuestion derived fromReliability (ICC/k)/validity (ICC/k)
1. How many days a week do you drink sugar-sweetened beverages?ENERGY-child questionnaire0.71/0.59
2. On a day you drink sugar-sweetened beverages, how many glasses/small bottles (250 mL), cans (330 mL) or big bottles (500 mL) do you drink?Combination ENERGY-child questionnaire and DOiT questionnaireENERGY
Glasses/small bottles (250 mL) 0.59/0.24
Cans (330 mL) 0.53/0.44
Big bottles (500 mL) 0.58/–0.01
DOiT
Cartons/small bottles (200 mL) 0.74/0.12
Glasses (200 mL) 0.45/0.47
Cans (330 mL) 0.61/0.24
Bottles (500 mL) 0.28/0.17
3. How many days a week do you drink energy drinks or sports drinks?Added based on Q1
4. On a day you drink energy drinks or sports drinks, how many small cans/bottles (250 mL) or big cans/bottles (500 mL) do you drink?Added based on Q2
5. How many school days per week do you eat sweets?DOiT questionnaire (adapted)
Original: ‘How many days a week do you eat sweets?’		0.66/0.60
6. When you eat sweets on a school day, how much sweets do you eat?DOiT questionnaire0.71/0.21
7. How many days in the weekend (Saturday/Sunday) do you eat sweets?DOiT questionnaire (adapted)
Original: ‘How many days a week do you eat sweets?’		0.66/0.60
8. When you eat sweets on a day in the weekend, how much sweets do you eat?DOiT questionnaire0.73/0.07
9. How many school days per week do you eat snacks?DOiT questionnaire (adapted)
Original: ‘How many days a week do you eat snacks?’		0.50/–0.11
10. When you eat snacks on a school day, how many small and large snacks do you eat?DOiT questionnaireSmall snacks 0.62/0.13
Large snacks 0.58/–0.08
11. How many days in the weekend (Saturday/Sunday) do you eat snacks?DOiT questionnaire (adapted)
Original: ‘How many days a week do you eat snacks?’		0.50/–0.11
12. When you eat snacks in the weekend (Saturday/Sunday), how many small and large snacks do you eat?DOiT questionnaireSmall snacks 0.53/0.44
Large snacks 0.64/0.08
13. How do you usually travel to school?DOiT questionnaireNot in test–retest study
14. How long does it take you to get from home to school?DOiT questionnaire+ENERGY child questionnaire (adapted)
Original: ‘If you walk/bike to school, how long does it take you?’		DOiT
Walking 0.65/zero variance
Biking 0.91/0.68
ENERGY
Walking 0.70/0.59
Biking 0.81/0.66
15. What do you usually do when you play outside at school?ENERGY-child questionnaire0.80/0.65
16. I like playing outside.ENERGY-child questionnaire—Adapted from Q20
17. I play outside never/1–2 times a week/3–4 times a week/5–6 times a week/every day.Added
18. When you play outside after school, what do you do?ENERGY-child questionnaire—Adapted from Q15
19. When you play outside after school, how long do you play? (fill in the number of hours per day in table)Added
20. I like playing sports.ENERGY-child questionnaire0.64/0.09
21. I play sports often/sometimes/never.Added
22a. Do you participate in sports in your free time?
22b. How many times per week do you do this sport?
22c. How many hours per day do you do this sport?
(fill in all sports that you do, the number of times and number of hours per week in the table)		DOiT questionnaire (adapted)
Original:

  1. ‘Do you participate in a sport at a sports club?’

  2. ‘How many hours a week do you do this sport?’

  3. ‘Do you participate in a second sport at a sports club?’

  4. ‘How many hours a week do you do this second sport?’

  5. ‘Do you participate in sports outside a sports club?’

  6. ‘How many hours a week do you do these sports?’

  1. 0.98/0.86

  2. 0.94/0.78

  3. 0.79/0.69

  4. 0.76/0.96

  5. 0.64/0.33

  6. 0.64/0.45

23. About how many hours a day do you usually watch television/DVDs/movies on the tablet or iPad in your free time? (fill in the number of hours per day in table)ENERGY-child questionnaire (adapted)
Original: ‘About how many hours a day do you usually watch television in your free time?’ (weekdays and weekend days)		Weekdays 0.67/0.63
Weekend days 0.68/0.56
24. About how many hours a day do you usually play games on your game computer, iPad, smartphone or surfing on the internet in your free time? (fill in the number of hours per day in table, weekdays and weekend days)ENERGY-child questionnaire (adapted)
Original: ‘About how many hours a day do you usually play games on a computer, or use your computer in your free time?’ (weekdays and weekend days)		Weekdays 0.67/0.35
Weekend days 0.67/0.65
25. How do you rate your health today?EuroQol EQ-5D-Y Dutch0.83/−0.51