Evaluation of a supermarket placement strategy to nudge healthier dietary habits: synopsis of the WRAPPED study.

BACKGROUND

Poor diet is a leading risk factor of non-communicable diseases. Product placement strategies in retail outlets can influence customers' food preferences. The United Kingdom government introduced legislation in October 2022 restricting chain retailers from using location promotions on unhealthy food and drinks. High-quality scientific evidence is needed to inform the inclusion of healthier product placement approaches into these regulations. In the context of Brexit, COVID-19 and the cost-of-living crisis, this study assessed whether positioning an expanded fresh fruit and vegetable section near store entrances in discount supermarkets, which do not routinely market produce this way, improved store sales, household purchasing and diet.

METHODS AND LIMITATIONS: This natural experiment had a prospective matched controlled cluster design, involving 36 stores (18 intervention and 18 control) across England. The intervention was implemented continuously for 6 months. Control stores were matched on store sales, customer profiles and neighbourhood deprivation. Participants were women, aged 18-60 years, with loyalty cards and were assigned to their primary store (n = 280 intervention and n = 300 control). Weekly store sales and household data from loyalty cards were provided by the collaborating supermarket chain. Dietary quality, household food waste and demographic characteristics were collected through questionnaires. A process evaluation and economic evaluation were completed.

RESULTS

Store-level sales of fruit and vegetables were greater in intervention stores than predicted at intervention implementation and 3 and 6 months' follow-up, equivalent to ≈ 2525, ≈ 1940 and ≈ 1450 extra portions per store per week, respectively. Effect sizes were somewhat stronger in stores where the produce section moved forwards more than 14 m. The proportion of households purchasing fruit and vegetables were somewhat protected among intervention compared to control participants after 3 and 6 months. Changes in dietary quality were small but generally in the expected direction for health benefit. Changes in frequency of household fruit and vegetable waste were negligible at 3 months' follow-up but increased at 6 months. The intervention was implemented according to the study protocol, with marked differences in the positioning of fresh fruit and vegetables between intervention and control stores post-intervention implementation. Fresh fruit and vegetable availability increased post intervention in intervention compared with control stores. Interviews with store staff demonstrated that changes in staff attitudes had a positive reinforcing effect on intervention implementation. Assessment of the policy context showed that stakeholders across the food system largely support the United Kingdom government's unhealthy placement ban; some felt it does not go far enough.

FUTURE WORK: This study shows that positioning produce sections near supermarket entrances can improve the nutrition profile of store sales and may improve household purchasing and diet. The United Kingdom Food (Promotion and Placement) Regulations could be refined to require a produce section near supermarket entrances to increase its health impact. Future research should continue to build the evidence for which healthy eating interventions are effective in retail outlets. Further evaluations of real-world supermarket intervention studies using robust scientific study designs are required, alongside process and economic evaluations, to provide evidence for policy intervention to improve retail food environments in the United Kingdom and internationally.

FUNDING: This synopsis presents independent research funded by the National Institute for Health and Care Research (NIHR) Public Health Research programme as award number 17/44/46.