Real-life effects of nudging and pricing strategies in the supermarket to promote healthy diets

Abstract

Abstract Background Unhealthy dietary patterns pose a major public health challenge. Individual-level efforts to promote heathy diets (e.g. nutrition education) have limited effect on the long term. Context-specific interventions focussing on point-of-purchase may create opportunities for sustainable dietary changes. We evaluated real-life effects of nudging and pricing strategies in supermarkets on dietary intake. Methods In this parallel cluster-randomised controlled trial, we randomized 12 Dutch supermarkets in socially deprived neighbourhoods to a control group (n = 6), or intervention group (n = 6). Healthy food nudges were implemented in intervention stores across 13 food groups, combined with healthy product price decreases and unhealthy product price increases. Eligible participants were aged 30-80 years and regular shoppers at participating stores. The primary outcome was dietary guideline adherence measured via an index score (0-150), at baseline and after 3, 6 and 12 months. Secondary outcomes included parameters of cardiometabolic health (HbA1c, lipid profile, and waist circumference), the percentage of healthy food purchases in the supermarket, socio-cognitive factors, and supermarket customer satisfaction. Effects were analysed with linear mixed models. Results This study included 173 participants from intervention clusters and 220 from control clusters. Preliminary evaluation of the 3-month follow-up data revealed no effectiveness of the nudging and pricing strategies compared to the control supermarkets in terms of dietary guideline adherence (β -0.8, 95%CI -4.2; 2.7). Results on all outcomes will be available at time of the conference. Conclusions This novel supermarket trial is the first to evaluate real-life long-term effects of nudging and pricing strategies based on a comprehensive set of study outcomes and using a strong methodological design. Findings can direct future design of context-specific interventions focussing on the promotion of healthy diets. Key messages • Context-specific interventions focussing on point-of-purchase may create opportunities for sustainable dietary changes. • Findings from this supermarket trial testing real-life and long-term effects of nudging and pricing strategies can direct future design of context-specific interventions focussing on healthy diets.