The impact of price promotions on confectionery and snacks on the energy content of shopping baskets: a randomised controlled trial in an experimental online supermarket

Poor diets, including overconsumption of foods high in fat, sugars, and salt (HFSS) increases the risk of premature death (1) . In an attempt to limit purchasing and subsequent consumption, the government in England has passed legislation to limit some price promotions of HFSS foods within supermarkets from October 2022 (2) , but evidence regarding the likely impact of these policies, espe-cially in online settings, is limited. This study aimed to determine whether there were any differences in the energy and nutrient content of shopping baskets after removing promotions on HFSS foods in an online experimental supermarket.UK adults (n = 511) were asked to select food from four categories with a £10 budget in an online experimental supermarket: confectionery; biscuits and crack-ers; crisps, nuts and snacking fruit; and cakes and tarts. They were randomly allocated to one of two trial arms: (1) promotions present (matched to promotion frequency seen in a major UK retailer) (n = 257), or (2) all promotions removed from all products within the target food categories (n = 254). The primary outcome analysis used linear regression to compare the total energy (kJ) of items placed in shopping baskets when promotions were present vs. absent, while secondary analyses investigated differences in nutrients and energy purchased from individual food categories. Ethics approval was granted by the Central University Research Ethics Committee, University of Oxford (Ref: R65010/RE006) and participants provided informed consent. Mean energy in food selected without promotions was 21,573 kJ per basket (SD 6776), compared to 23,162 kJ