The process evaluation of two interventions aimed at portion size in worksite cafeterias

Abstract

In a previous study, the effectiveness of introducing a small meal in addition to the existing size and a proportional pricing strategy have been assessed in Dutch worksite cafeterias. To assess the degree of implementation and to inform the design of future interventions, the present study aimed to describe the process evaluation of both interventions. Process evaluation components from Baranowski and Stables, and Rogers (i.e. Recruitment, Maintenance, Context, Resources, Implementation, Exposure, Contamination, and Continued use) were chosen as a theoretical basis. The process evaluation involved qualitative (e.g. structured observations, semi-structured interviews) and quantitative data (e.g. consumer questionnaires) collected from 17 intervention and eight control worksite cafeterias. In all intervention cafeterias, two portion sizes were offered. The pricing instructions were followed in 13 intervention cafeterias. The cafeterias managers indicated that they did not consider offering large and small meals as being complex, risky or time-consuming to implement. Some managers perceived the consumer demand as high, others as (too) low. One year after the study had ended, nine of the intervention cafeterias had continued (at least partly) to follow the protocol. Offering a smaller portion size in addition to the existing size, as well as proportional pricing, was generally implemented as prescribed by the protocol and can be considered promising in terms of continued use. However, additional efforts are needed to make the intervention more effective in motivating consumers to replace their large portion with a small portion.