Does supermarket placement affect intention to buy healthy and unhealthy foods?

Principal Investigator:  Janis Baird and Christina Vogel, Professor of Public Health and Epidemiology and Principal Research Fellow in Public Health Nutrition respectively, MRC Lifecourse Epidemiology Centre, University of Southampton

Team: Dr Sarah Crozier, Senior Statistician, MRC Lifecourse Epidemiology Centre, University of Southampton

Sarah Jenner, Senior Research Assistant at University of Southampton

Dr Sarah Muir, Senior Research Fellow, University of Southampton

Professor Marcus Munafo and Dr Olivia Maynard, Bristol University

Ravita Taheem, Southampton City Council, Sure Start Children’s Centres

Megan Brook, Public Contributor

Tiana Chadwick, Public Contributo

Start date: 1 October 2019

End date: 28 February 2022

Background

Poor diet has been recognised as a major contributor to the burden of non- communicable diseases in the UK and costs the NHS approximately £6 Billion annually.

Most adults in England consume too much salt, saturated fat and free sugar, and do not eat the recommended five daily portions of fruit and vegetables. Among low-income groups these trends are more extreme. Almost 90% of UK grocery sales occur within supermarkets4 and their subtle use of marketing techniques influences the food choices of an almost captive market. Women of childbearing age are an important target group to study because they remain primarily responsible for domestic food tasks such as shopping and cooking and their nutrition status influences the short and long-term health of their children.

Our prior work in Hampshire showed that the diets of women with low educational attainment were more affected by less healthy supermarket environments than women with higher attainment. Shopping at less healthy discount and small supermarkets, with poorer availability, pricing and placement of healthy foods, was associated with poor dietary quality among women who left school aged 16 years but not among those with degree qualifications. UK government policy recognises that more effort is needed to develop interventions to improve health equitably and is introducing legislation on product placement initiatives to support families to make healthier food choices in supermarkets.

Research using adequately powered clustered randomised controlled trials in supermarkets is limited, largely due to the complexity and large number of stores required. Evaluating changes in supermarket layout is notoriously challenging due to differing health and business agendas and randomisation at the store level requires commitment that is problematic in this highly competitive, commercial setting. Virtual supermarkets offer a viable alternative to investigate the likely impact of supermarket-based, healthy eating policy options using robust trial designs. Additionally, neuroscience techniques, such as eye-tracking, offer objective evidence that complements self-report behaviours, and facilitate a deeper understanding of the cognitive mechanisms underlying health-related behaviours. Such techniques have been used to examine how product placement facilitates customers’ visual attention, however there is a gap in understanding of how visual attention differs according to the healthfulness of products, particularly while placed in prominent in-store locations and whether visual attention differs according to customer’s socioeconomic position.

This study aims to use experimental randomised trials and a virtual supermarket setting to determine differences in visual attention and intended purchase of healthy, unhealthy and non-food products placed in prominent in-store locations such as checkouts. It will also assess effect modification by educational attainment on these relationships to explore potential effects on inequalities.

This is the first of two phases of research assessing visual responses to product placement. In this phase, heat mapping technology using Qualtrics software determined whether interest in and intended purchase of products in prominent in-store locations differed if the products were healthy, unhealthy or non-food items. We assessed effect modification by educational attainment to explore potential effects on inequalities. Women with young children (n=230), recruited through Sure Start Children’s Centres, early years setting and other community groups in Hampshire, undertook shopping trips in a virtual supermarket to assess whether their purchasing intentions differ if unhealthy foods, healthy foods or non-food items are placed in prominent positions (store entrances, checkouts and end of aisle). Preliminary findings indicated differences in women’s intention to buy certain types of products according to their educational attainment. Women with no educational qualifications beyond aged 16 years were intent on purchasing fewer healthy products when they were placed in prominent locations whereas those with higher educational attainment were intent on buying significantly more healthy products. A total of 230 women participated in phase I, exceeding our target sample size of 52.

The study

Women were shown a series of pictures representing six journeys through a supermarket. Pictures focused on the areas in a store where most shoppers usually pass through including the store entrance, end-of-aisles and checkouts.

In the first three journeys, women needed to click all items they were interested in. In the last three journeys they needed to click all the items they would intend to buy if this was a real shop. Each set of journeys included a healthy journey, unhealthy journey and a non-food journey.

What were the results?

• 201 women took part in a virtual supermarket survey.

• Overall, women in the study showed more interest in unhealthy products than healthy or non-food items. At checkouts, however, they did show more interest in non-food items.

• Women intended to buy more healthy and non-food items than unhealthy food items. On average they wanted to buy 12.9 healthy products per shop compared to 11.5 unhealthy products.

What difference will this make?

Unhealthy products can be interesting to women who shop at supermarkets but they have higher intentions to buy healthy and non-food items in noticeable places in stores.

Supermarkets usually place unhealthy foods in noticeable places to make profits. Replacing these unhealthy foods with healthy or non-food items will just as likely, if not more successfully, lead to purchases. This can help families lead healthier lives.

Why is this important for patients, health and care providers and policy makers ?

Placing unhealthy foods in noticeable places can lead to impulse purchases of foods that can lead to obesity. Our study shows that women do not intend to buy these foods but may show interest in them.

Since 2022, UK policy has banned the placement of some unhealthy foods at noticeable places in supermarkets. This research provides evidence that customers likely support this policy as they would like to buy healthy and non-food items from these locations.

What we are going to be doing next?

• We wanted to further understand how attention to healthy, unhealthy and non-food items differ in noticeable places in supermarkets. We therefore ran eye-tracking experiments with 70 women in Hampshire. Data are being analysed.

• We plan to report the results of our survey and eye-tracking studies to policymakers (e.g. Department of Health and Social Care and Public Health England) via a policy brief.

• We also aim to share our results with families via Sure Start Children’s Centres, Facebook and Local Schools.

• We have plans to share our findings at public health conferences and in an academic journal.