Table 1 Assessment of potential mediators

Attitude towards consuming 200 grams of vegetables a day^a

I think eating 200 grams of vegetables per day is …

Very unhealthy (1) – very healthy (5)

Very unimportant (1) – very important (5)

Very disgusting (1) – very delicious (5)

Perception of vegetables as being expensive^a

I think eating 200 grams of vegetables per day is …

Very expensive (1) – very cheap (5)

Self-efficacy^a

Do you think you can eat 200 grams of vegetables per day in the next 6 months if you really want to?

Definitely not (1) – definitely (5)

How difficult or easy do you think it is to eat 200 grams of vegetables each day in the next 6 months?

Very difficult (1) – very easy (5)

Subjective norm^a

Most people who are important to me…

Definitely not (1) – definitely (5)

… Think I should eat 200 grams of vegetables each day

… Eat 200 grams of vegetables each day

Intention^a

Do you intend to eat 200 grams of vegetables a day?

Definitely not (1) – definitely (5)

General self-regulation^a

When I have a goal, I can usually plan how to reach it

Definitely not (1) – definitely (5)

I give up quickly (reversed)

I have trouble to make plans that help me to reach my goals (reversed)

I have a hard time setting goals for myself (reversed)

I set goals for myself and keep track of my progress

If I try to change something, I pay attention on how I am doing

Action planning^b

I have a clear plan for…

Completely disagree (1) – completely agree (4)

… When I am going to eat more vegetables

… Which kinds of vegetables I am going to eat more

… How much vegetables I am going to eat more

Coping planning^b

I have a clear plan for…

Completely disagree (1) – completely agree (4)

… What I am going to do when something interferes with my plans to eat more vegetables

… What I am going to do in situations in which it can be more difficult to eat more vegetables

Perception of availability in supermarket^a

In the store where I usually do my shopping, there is a sufficient amount of vegetables available

Completely disagree (1) – completely agree (5)

Availability of vegetables at home^a

How often do you have vegetables available at home?

Never (1) – always (5)