Protocol for a quasi-experimental analysis: using retail sales data to evaluate impacts of the high fat, sugar and salt (HFSS) product placement restrictions legislation in England

Introduction From 1 October 2022, new legislation in England restricts the placement of some food and drink products high in fat, sugar and salt (HFSS) in stores with a sales floor larger than 185.8 m2 (2000 sq ft). ‘Less healthy’ products in 13 categories, which fail the UK Nutrient Profiling Model, cannot be placed at store entrances, ends of aisles, at checkouts or their online equivalents. Reducing the prominence of ‘less healthy’ foods should decrease impulse purchases and excess calorie intake. Stores in Scotland, Wales and Northern Ireland are exempt, but the UK Devolved Nations are considering similar rules.

Methods and analysis Daily store-level sales and product data from multiple UK retailers will be used to evaluate the legislation’s impacts in relation to HFSS sales, retailer product portfolios and equitability across different areas in England. Food and drink sales data from 18 months pre-policy and 12 months post-policy implementation will be gained for a sample of stores. Controlled interrupted time series modelling will be used to estimate policy effects, with stores from Scotland and Wales acting as controls. Online sales are excluded.

Stores from study partner retailers were identified using Geolytix retail points data. Selected stores were defined as mid-sized or larger (>280 m) by Geolytix, to ensure legislation eligibility. 160 stores in England (intervention sample) and 50 stores in Scotland/Wales (control sample) were selected for each partner retailer. For each retailer, we sampled equal intervention store numbers (n=16) across each tenth of the Priority Places for Food Index (PPFI). Weighting was used to ensure maximum sample variability by store size and area demographic characteristics (urban/rural status) within each PPFI tenth.

Ethics and dissemination This study has received approval from the Business, Environment and Social Sciences ethical review board at the University of Leeds (AREA 21–063).

Findings at the retailer and cross-retailer levels will be published in academic journal articles as well as industry-facing reports coproduced by Institute of Grocery Distribution. Through meetings and workshops, we will disseminate results to inform future business practice and policymaking across the UK Devolved Nations.

Registration Protocol was first published on Open Science Framework https://osf.io/jp9eh.