Page 123 - ON THE WAY TO HEALTHIER SCHOOL CANTEENS - Irma Evenhuis

recognised the usefulness of the collaboration between school, caterer and municipality health services and to create aims and actions together, by means of the advisory meeting with the participation of different stakeholders. Such community support has previously been identified as one of the conditions influencing implementation of school health programmes [68].
In the process evaluation stakeholders raised some concerns about the financial effects caused by a healthier canteen. Some canteens experienced lower, while in others higher sales were observed. Other research also notes the financial concerns [209], but also shows that vending machines with a healthier offer maintained their revenues [43]. Nevertheless, these concerns among stakeholders should be recognised and taken into consideration.
Methodological considerations
Each chapter in this thesis has already addressed its specific strengths and limitations. This section therefore describes the more general methodological considerations.
Whom to include in your study?
A strength of our studies is the continuous collaboration between research, practice and policy. However, there is a risk of selection bias with regard to the inclusion of stakeholders, schools and students. Multiple related strengths and limitations can be identified in our studies, which need to be addressed.
A strength of such continuous collaborations is that it improves alignment between
scientific evidence and applicability in daily practice, and it increases collaboration and
sense of ownership among stakeholders and subsequent uptake of study results [60].
Another strength is that a wide range of stakeholders with different levels of experience
of previous canteen guidelines and with different degrees of willingness to use the new 7 guidelines was included in the needs assessment. We took into account Roger’s diffusion
of innovation theory that explains how innovations spread [94]. According to this theory adopters of an innovation can be classified in five categories on the basis of the pace of adoption: innovators, early adopters, early majority, late majority and laggards. It is reasonable that stakeholders in different categories experience different barriers and facilitators with regard to implementing the guidelines.
In contrast, in order to evaluate the implementation plan, we only could include schools and caterers who were willing to start implementing the Guidelines for Healthier Canteens at an early stage. Therefore, our results pertain only to such early adapters. This may have made the results less generalisable to schools less interested in (making changes in) a healthy food environment at school. This is a limitation, as it may have resulted in smaller differences between the intervention and control group as both groups were motivated to start working with the guidelines, even though the control group received the guidelines without support.
With regard to the inclusion of students, another limitation might be that we included mainly second year students (13-15 years old). This group was selected because they were more adapted to the school environment compared to the first-year students, and in the third class and higher students were less present at school, due to external internships (in
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