Discussion
All the interventions tested in this study reduced the energy content of participants’ baskets, showing as a proof-of-concept that these approaches might have the potential to lower energy purchased from food delivery platforms. The greatest decrease was in the intervention that repositioned both foods and restaurants purely based on energy content. All interventions repositioning options purely based on energy content led to a decrease in total basket price, which may represent an implementation barrier for industry. An intervention designed to mitigate the potential reduction in revenue was successful in its aim, but less effective or no different in reducing the energy content of foods selected than the other price-agnostic interventions.One of the strengths of this study is its relevance to real food purchasing platforms. The sample was large and broadly representative of the UK population and participants were free to choose a meal from a virtual site that closely mimicked online delivery platforms. The energy purchased in this study was comparable to energy content for takeaway food reported previously (medians for five takeaway food types of 1125–1820 kcal per meal) [As a proof-of-concept, this study shows the potential impact of repositioning options in food delivery platforms to promote health outcomes and explores strategies to promote health outcomes whilst protecting the bottom line of restaurants and delivery platforms. Voluntary implementation in real-world settings may be challenging, as was previously seen when voluntary food reformulation targets resulted in limited changes [This study focused on prominent positioning of items at the top of the page, based on evidence from previous research that primacy effects are a critical factor in boosting selection in online settings [It has been suggested that interventions focusing on changing the choice architecture in people’s environments may reduce disparities due to the universal application of interventions [Post hoc we observed two other factors which may warrant further exploration. First, interventions that altered the restaurant position were more effective when participants accessed the study on a mobile phone compared to a desktop computer. This seems plausible since mobile device users may need to scroll further to see the same numbers of restaurants as on a desktop or laptop, and therefore be more likely to click on restaurants nearer the top. Second, the effect of interventions was smaller in the restaurants only repositioning conditions among participants who used food delivery platforms more often. One possible explanation for this is that frequent users may know more about how these platforms work, and more quickly search for what they want to select, rather than browsing.