Constructs and items of the determinant questionnaire

Constructs with items	Response categories
Personal
Attitude To eat fruit/vegetables every day makes me feel good To eat fruit/vegetables every day gives me more energy	5 point scale from 2 = I fully agree to -2 = I fully disagree
Self efficacy It is difficult for me to eat fruit/vegetables every day If I decide to eat fruit/vegetables every day, I can do it	5 point scale from -2 = I fully agree to +2 = I fully disagree
Liking I like to eat fruit/vegetables every day Fruit/vegetables taste good	5 point scale from 2 = I fully agree to -2 = I fully disagree
Preferences fruit Which of the following fruits do you like or dislike, list of 12 fruits: apple, bananas, pears, oranges, tangerines, plums, peaches, melon, strawberries, grapes, cherries, kiwis	5 point scale from 2 = like very much to -2 = dislike very much and 0 = have not tried
Preferences vegetables Which of the following vegetables do you like or dislike? List of 12 vegetables: tomatoes, cucumber, salad, cabbage, spinach, leak green beans, onion, carrots, broccoli, cauliflower, green peas	5 point scale from 2 = like very much to -2 = dislike very much and 0 = have not tried
Perceived barriers fruit I do not eat fruit because it takes too much time to eat I do not eat fruit because I want to eat something else (e.g. sweets) I do not eat fruit because my fingers get greasy when I eat it I do not eat fruit because it gets squeezed in the schoolbag	5 point scale from 2 = I fully agree to -2 = I fully disagree
Perceived barriers vegetables I do not eat vegetables because it takes too much time to eat I do not eat vegetables because I am still hungry after having eaten them I do not eat vegetables because I want to eat something else (e.g. sweets) I do not eat vegetables because they get squeezed in the schoolbag	5 point scale from 2 = I fully agree to -2 = I fully disagree
Knowledge fruit How much fruit do you think you should eat to have a healthy diet?	1 = no fruit, 2 = 1–3 pieces per week, 3 = 4–6 pieces per week, 4 = 1 piece per day, 5 = 2 pieces per day, 6 = 3 pieces per day,7 = 4 pieces per day, 8 = 5 pieces per day or more recoded: correct knowledge = 5–8
Knowledge vegetables How many vegetables do you think you should eat to have a healthy diet	1 = no vegetables, 2 = 1–3 portions (serving spoons) per week, 3 = 4–6 portions per week, 4 = 1 portion every day,5 = 2 portions every day, 6 = 3 portions every day, 7 = 4 portions every day, 8 = 5 or more portions every day recoded: correct knowledge = 6–8
Perceived social environmental
Modelling My mother eats fruit/vegetables every day My father eats fruit/vegetables every day My best friend eats fruit/vegetables every day	5 point scale from 2 = I fully agree to -2 = I fully disagree
Active encouragement My mother encourages me to eat fruit/vegetables every day My father encourages me to eat fruit/vegetables every day	5 point scale from 2 = I fully agree to -2 = I fully disagree
Demanding Do your parents demand that you eat fruit/vegetables every day?	5 point scale from 2 = yes, always to -2 = never
Allowing Are you allowed to eat as much fruit/as many vegetables as you like at home?	5 point scale from 2 = yes, always to -2 = never
Facilitating Does your mother or father usually cut up fruit/vegetables for you in between meals?	5 point scale from 2 = yes, always to -2 = never
Perceived physical environment
Home availability If you tell at home what fruit/which vegetables you would like to eat, will it be bought? Are there usually different kinds of fruits/vegetables available in your home? Is/are there usually fruit/vegetables available at home that you like?	5 point scale from 2 = yes, always to -2 = never
School availability Can you get fruit/vegetables at school either by buying it or getting it for free?	5 point scale from 2 = yes, always to -2 = never
Availability at friends Can you get fruit/vegetables at you friends' house, when you spend the afternoon there?	5 point scale from 2 = yes, always to -2 = never
Availability at the club Can you get fruit/vegetables at the place where you have your leisure time activity (e.g. club, sports place) either by buying it or getting it for free?	5 point scale from 2 = yes, always to -2 = never