A randomised experiment of health, cost and social norm message frames to encourage acceptance of swaps in a simulation online supermarket

Amanda Bunten, Lucy Porter*, Jet G. Sanders, Anna Sallis, Sarah Payne Riches, Paul van Schaik, Marta González-Iraizoz, Tim Chadborn, Suzanna Forwood

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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Abstract

Offering lower-energy food swaps to customers of online supermarkets could help to decrease energy (kcal) purchased and consumed. However, acceptance rates of such food swaps tend to be low. This study aimed to see whether framing lower-energy food swaps in terms of cost savings or social norms could improve likelihood of acceptance relative to framing swaps in terms of health benefits. Participants (n = 900) were asked to shop from a 12-item shopping list in a simulation online supermarket. When a target high-energy food was identified in the shopping basket at check-out, one or two lower-energy foods would be suggested as an alternative (a “swap”). Participants were randomised to only see messages emphasising health benefits (fewer calories), cost benefits (lower price) or social norms (others preferred this product). Data were analysed for 713 participants after exclusions. Participants were offered a mean of 3.17 swaps (SD = 1.50), and 12.91% of swaps were accepted (health = 14.31%, cost = 11.49%, social norms = 13.18%). Swap acceptance was not influenced by the specific swap frame used (all p > .170). Age was significantly and positively associated with swap acceptance (b = 0.02, SE = 0.00, p < .001), but was also associated with smaller decreases in energy change (b = 0.46, SE = .19, p = .014). Overall, offering swaps reduced both energy (kcal) per product (b = -9.69, SE = 4.07, p = .017) and energy (kcal) per shopping basket (t712 = 11.09, p < .001) from pre- to post-intervention. Offering lower-energy food swaps could be a successful strategy for reducing energy purchased by customers of online supermarkets. Future research should explore alternative solutions for increasing acceptance rates of such swaps.

Original languageEnglish
Article number0246455
Number of pages16
JournalPLoS ONE
Volume16
Issue number2
DOIs
Publication statusPublished - 17 Feb 2021

Bibliographical note

Funding Information: This work was completed as part of the usual business activities of Public Health England and received no additional funding. LP, JGS and MGI were on placement at Public Health England as part of the RCUK internship scheme for part of their involvement in this work.

Open Access: This is an open access article distributed under the terms of the Creative Commons Attribution 3.0 IGO (CC BY 3.0 IGO) License which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.

Publisher Copyright: © 2021 Public Health England.

Citation: Bunten A, Porter L, Sanders JG, Sallis A, Payne Riches S, Van Schaik P, et al. (2021) A randomised experiment of health, cost and social norm message frames to encourage acceptance of swaps in a simulation online supermarket. PLoS ONE 16(2): e0246455.

DOI: https://doi.org/10.1371/journal.pone.0246455

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