Krachtvoer: effect evaluation of a Dutch healthful diet promotion curriculum for lower vocational schools

Objective: The aim of this study was to assess the behavioural effects of a schoolbased
healthful diet promotion intervention implemented in lower vocational
schools.
Design: A cluster-randomised pre-test–post-test experimental design was used,
and data were collected by means of written questionnaires.
Setting: Students of 18 Dutch lower vocational schools.
Subjects: The final sample consisted of 10 experimental schools with 13 teachers,
37 classes and 879 students, and eight control schools with 10 teachers, 31 classes
and 734 students (total n51613).
Results: Fixed regression analyses revealed beneficial effects on the behavioural
measures relating to fruit intake (as assessed by a food frequency measure and
fruit consumption during the previous day), and most behavioural measures
related to high-fat snack intake (food frequency measure, and number of snacks
and total fat intake from snacks during the previous day). The behavioural effects
relating to breakfast habits were limited. Some positive behavioural effects
occurred in the total target population, others mainly or only among students with
more unfavourable intakes at baseline. Mixed regression analysis found comparable
regression coefficients for the behavioural outcomes, but the effects
related to fruit intake were no longer statistically significant.
Conclusions: Although we did not find the expected effects on all outcome
indicators, the total pattern of results suggest that Krachtvoer offered a surplus
value over existing curricula. However, some programme elements need to be
revised to improve effectiveness and prevent negative effects, and more information
is needed about the long-term effects of the programme.