The effect of nudges aligned with the renewed Flemish Food Triangle on the purchase of fresh fruits: An on-campus restaurant experiment

Abstract Objective This study examined the effect of nudges, inspired by the recently renewed Flemish Food Triangle, on fruit sales in a Belgian on-campus university restaurant. Methods In this mixed-method real-life experiment, nudges were added weekly over a period of four consecutive weeks: placement of (1) Food Triangle posters in the restaurant, (2) ‘green heart’ icons above the fruit stands, and (3) substitution and (4) social norm messages at the fruit stands. During baseline (no intervention) and all intervention weeks, dessert sales were registered. Short interviews were used to ask customers about their perceptions regarding the intervention. Follow-up measurements (7 and 30 weeks later) evaluated the longer-term effectiveness, while all nudges remained in place. Dessert sales were analyzed separately for both sexes, students and staff categories (based on academic degree). Results Compared to baseline, the combination of the Food Triangle and the green heart intervention materials in week 2 resulted in significant increases in fruit consumption across almost all subgroups. The other intervention materials used in the current study had rather limited effects in the short term. After 7 weeks of follow-up, significant fruit sale increases were established for all subgroups compared to baseline. At 30 weeks follow-up, the effect for staff B (Bachelor's degree) disappeared. The majority of the respondents (66.4%) had noticed at least one of the nudges, while only 3.4% indicated to have adjusted their dessert choice as a result of the nudges. Conclusions The combination of nudges was effective in the long term and increased fruit purchase in nearly all subgroups. Short interviews show that a more active approach may be needed to increase effect sizes.