Co-designing "healthy eating" interventions with supermarket retailers: Consumers did not fall in the trap & altered shelf placement alone did not improve the (official) healthiness of food purchases

The effect of a shelf placement intervention on sales of healthier and less healthy breakfast cereals in supermarkets: A co-designed pilot study. Leanne Young et al. Social Science & Medicine, September 1 2020, 113337. https://doi.org/10.1016/j.socscimed.2020.113337

Highlights

• Co-designing healthy eating interventions with supermarket retailers is feasible.

• Altered shelf placement alone did not improve the healthiness of food purchases.

• Customers noted brand preferences and price as key determinants of purchases.

• In-store promotions present opportunities to improve healthiness of food purchases.

• Product promotional strategies should align with healthy eating interventions.

Abstract: Supermarkets are the principal source of grocery food in many high-income countries. Choice architecture strategies show promise to improve the healthiness of food choices. A retailer-academic collaboration was formed to co-design and pilot selected commercially sustainable strategies to increase sales of healthier foods relative to less healthy foods in supermarkets. Two co-design workshops, involving supermarket corporate staff and public health nutrition academics, identified potential interventions. One intervention, more prominent shelf placement of healthier products within one category (breakfast cereals), was selected for testing. A pilot study (baseline, intervention and follow-up, 12-weeks each) was undertaken in six supermarkets (three intervention and three control) in Auckland, New Zealand. Products were ranked by nutrient levels and profile, and after accounting for the supermarkets’ space management principles, healthier products were placed at adult eye level. The primary outcome was change in sales of healthier products relative to total category sales. Secondary outcomes were nutrient profile of category sales, in-store product promotions, customer perceptions, and retailer feedback. There was no difference in proportional sales of more prominently positioned healthier products between intervention (56%) and control (56%) stores during the intervention. There were no differences in the nutrient profile of category sales. A higher proportion of less healthy breakfast cereals were displayed in intervention versus control stores (57% vs 43%). Most customers surveyed supported shelf placement as a strategy (265, 88%) but noted brand preferences and price were more salient determinants of purchases. Retailers were similarly supportive but balancing profit, health/nutrition and customer satisfaction was challenging. Shelf placement alone was not an effective strategy to increase purchases of healthier breakfast cereals. This study showed co-design of a healthy eating intervention with a commercial retailer is feasible, but concurrent retail environment factors likely limited the public health impact of the intervention.

Keywords: SupermarketsDietsShelf placementCo-designNutritionChoice architecture

4. Discussion

In this pilot study, the co-designed intervention, more prominent shelf placement of healthier products, had no effect on healthier breakfast cereal sales. Whilst small increases in sales were shown in two cereal segments and for two of the three intervention stores these were not statistically significant. Altering the shelf placement of products was the sole change made to the food category; therefore, this study was useful to test the effectiveness of this strategy in isolation. This single strategy study was unique compared to many supermarket interventions (Adam and Jensen, 2016; Hartmann-Boyce et al., 2018), which commonly test multiple strategies (signage, placement, education, price) and therefore the effect of individual strategies within a multi-faceted intervention is usually less able to be determined (Cameron et al., 2016). Despite this, a systematic review found that single and multi-strategy interventions share the same high success rate (70%) (Cameron et al., 2016). Inclusion of a whole category rather than individual products within a category was also a distinctive feature of this study. However, the findings suggest that shelf placement alone (in the absence of other strategies) is a weak lever for influencing the healthiness of shopper purchases in the breakfast cereal category.

Secondly, there was no effect of the shelf placement intervention on the nutritional composition of sales within the breakfast cereal category. This intervention was implemented in a ‘real world’ supermarket setting. Therefore, the nutritional ranking of breakfast cereals by cereal category segment (by researchers) was subject to the usual supermarket space management criteria for shelf placement. These included segmentation (e.g. all oats grouped together), brand blocking (brands located together), pack size blocking (similar sized packages located together) and visual appeal of products on shelves that aim to make product selection easy for shoppers. These requirements and that just over half (56%) of the products did not change position resulted in relatively small differences in the nutritional composition of products located in prominent versus non-prominent shelf locations, which are likely reasons for the lack of effect on nutrient sales. Interviews with store staff supported the notion that space management criteria compromised the ideal placement of products. Furthermore, the range of nutrient composition values (e.g. energy) was narrow for some smaller segments, e.g. biscuits (n = 12).

Thirdly, in-store product display promotions appear to have interacted with the shelf placement intervention. There were multiple breakfast cereals on in-store displays across all six stores (n = 1268), with a slightly higher proportion in intervention stores (54%) and a higher proportion of less healthy, less prominent products compared to control stores. Per store, there were 19 breakfast cereals (includes flavour variants of products) each week in aggregated displays (4–6 actual display areas per store featuring multiple products and product variants) (data was collected at one time point each week). Store managers are provided with guidance from a national display matrix, which provides product promotional options within a category/segment for each designated display space. When products are on promotion the entire brand range may be included (healthy and less healthy). It is possible that at the time of the audit the healthier choices had already sold out on displays and gaps were filled by other, less healthy products in the range. It is also plausible that the higher number of promotions for less healthy products in intervention stores may have been orchestrated by store personnel (consciously or unconsciously) to feature higher selling, more profitable products, that had been moved to less prominent shelf positions, and thus counteracted shelf prominence of healthier products. Data on in-store promotions were not collected in the pre- or post-intervention periods therefore change in the type of promotions over time could not be determined.

The lack of effect of prominent placement on product sales shown in our study generally aligns with findings from Foster et al. (2014) who suggested that brand loyalty and product preferences may be dominant in this particular category. Brand loyalty in the breakfast cereal category also emerged as a strong theme from our shopper survey, with shoppers commenting that they tended to purchase the same brand repeatedly. Similarly, strong shopper preferences and habitual purchase behaviours were found in an experiment examining the effects of a change of placement for types of bread (de Wijk et al., 2016). The bread category was described as less able to be ‘nudged’ because a nudge needs to be of sufficient strength to overrule usual purchase habits. Other mechanisms in the environment can also influence habitual health behaviours and consumer choices (Wilson et al., 2016), for example, product price, nutrition labelling/information and availability (Arno and Thomas, 2016). Price was another key factor that shoppers highlighted in our current study as influencing product choice, although brands with high loyalty tend to use price less to generate sales compared to minor brands (Empen et al., 2011).

This study had several strengths. It utilised co-design to enhance the likely fiscal sustainability of the intervention. This process allowed a strong working relationship to be built with the retail partner, which facilitated intervention delivery, access to sales and promotional data, and possible future research opportunities. Intervention selection was informed by commercial knowledge and not preconceived by researchers. A single strategy, more prominent shelf placement of healthier products within an entire food category, was piloted in a real-world environment using a controlled study design to determine potential effectiveness. Inclusion of pre-intervention and follow-up periods allowed measurement of change over time. Supermarket sales data was used as a direct measure of change in shopper purchases to determine the effect of the intervention rather than reliance on self-reported purchases (Bandy et al., 2019). Weekly product auditing and retailer follow-up of anomalies resulted in high intervention compliance.

The study was however, limited by its small sample size (6 stores) and lack of randomisation. Although, it has been acknowledged that randomisation in supermarket intervention design is difficult due to the innate nature of real-life implementation (Escaron et al., 2013). The original aim was to pilot the intervention in a limited number of stores with the intention that if findings were promising, a larger sufficiently powered randomised controlled trial would be conducted. However, our experience working alongside a major retailer suggests that successful interventions would likely be rolled out to a larger number of stores very quickly, with little time for a larger randomised controlled study to be organised. Other limitations to note briefly include lack of alignment of the intervention with other concomitant breakfast cereal promotions (price reductions, mailers, and in-store displays), lower compliance with product planograms in control stores, selection of a category where customer brand loyalty and purchase habits are strong which likely minimised potential impact, and relatively small difference in the healthiness of prominent and less prominent products. More research is needed to understand the effects of the range of in-store promotions, including price, on sales within the supermarket environment. Other categories where shoppers do not purchase the same products habitually may also have been more suited to testing shelf placement, for example, convenience foods, ready meals or soups.