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.
Highlights
Overweight and obesity is the norm in the UK; at the latest estimate, 66% of men and 57% of women had overweight or obesity [1]
This study tested whether framing lower-energy food swaps in terms of cost benefits or social norms would be more effective at encouraging participants to accept such swaps compared to a health message
It was hypothesised that (i) the cost and social norms frames would be more effective than the health frame, and (ii) the cost frame would have a higher impact on swap acceptance for individuals on a low income compared to those on a high income
Summary
Overweight and obesity is the norm in the UK; at the latest estimate, 66% of men and 57% of women had overweight or obesity [1]. Obesity is linked to an increased risk of diseases such as cardiovascular disease and cancer [2], is associated with increased all-cause mortality [3], and significantly reduces individuals’ quality-adjusted life years [4]. One of the primary causes of weight gain is an imbalance in the amount of energy consumed against the amount of energy expended through activity and basal metabolic rate [5,6,7], with other factors such as body weight and physical fitness influencing this relationship [8]. Excess energy intake is facilitated when energy-dense foods are highly visible, widely available and accessible, in what some have termed the “obesogenic” environments of modern society [9]. Making small changes to the environments in which people choose and consume foods could be a viable strategy to reduce energy intake [10]. Examples of specific techniques to do this include manipulating the proximity of certain food items in shops and cafeterias [11] or priming consumers with healthy eating messages in supermarkets [12, 13]
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