Table 1 Description of questions assessing self-reported outcome variables

Physical activity level

“How much do you exercise and exert yourself physically during leisure time?

If the amount varies a lot during the year, choose an option which best describes your AVERAGE situation.”

Four response categories:

1: During leisure time, I read, watch TV and do things where I don’t move much physically and which don’t exert me physically.

2: During leisure time, I walk, ski (cross-country), bicycle, or move physically in some other way (e.g. do gardening) for at least four hours a week.

3: During leisure time, I do dedicated fitness training for at least three hours a week.

4: During leisure time, I regularly exercise competitively several times a week.

Meal regularity

“How often do you eat BREAKFAST (bread, cereals, porridge, yogurt, or something similar in the morning before going to school or work)?”

“How often do you eat LUNCH (a warm meal at school, work or home or elsewhere around noon)?”

“How often do you eat DINNER (a warm meal in the afternoon or the evening)?”

Each has four response categories:

1: every day;

2: 4–6 times a week;

3: 1–3 times a week;

4: less than once a week.

Bedtime

“At what time do you usually go to sleep in the evenings preceding school-/work-days?”

Response categories from 22:00 (or before) to 03:00 (or later) with a 30 min range of accuracy.