Effects of Labelling and Increasing the Proportion of Lower-Energy Density Products on Online Food Shopping: A Randomised Control Trial in High- and Low-Socioeconomic Position Participants

Abstract

Reducing the energy density (ED) of product selections made during online supermarket food shopping has potential to decrease energy intake. Yet it is unclear which types of intervention are likely to be most effective and equitable. We recruited 899 UK adults of lower and higher socioeconomic position (SEP) who completed a shopping task in an online experimental supermarket. Participants were randomised in a 2 × 2 between-subjects design to test the effects of two interventions on the ED of shopping basket selections: labelling lower-ED products as healthier choices and increasing the relative availability of lower-ED products within a range (referred to as proportion). Labelling of lower-ED products resulted in a small but significant decrease (−4.2 kcal/100 g, 95% CIs −7.8 to −0.6) in the ED of the shopping basket. Increasing the proportion of lower-ED products significantly decreased the ED of the shopping basket (−17 kcal/100 g, 95% CIs −21 to −14). There was no evidence that the effect of either intervention was moderated by SEP. Thus, both types of intervention decreased the ED of foods selected in an online experimental supermarket. There was no evidence that the effectiveness of either intervention differed in people of lower vs. higher SEP.

Factors associated with ordering food via online meal ordering services

“…Recent research provides some indication of how online purchase environments can be altered to encourage healthier selections. The strategies identified in online grocery shopping contexts include explicitly drawing attention to healthier choices, increasing the ratio of available healthier options relative to unhealthier options and providing filters that enable shoppers to refine their searches according to specific nutrition-related criteria (30,31) . It remains to be seen whether such strategies would be effective in the online meal ordering context, and particularly among those population segments identified in this and previous research as being most likely to engage in this form of food purchase.…”

Nudging customers towards healthier food and beverage purchases in a real-life online supermarket: a multi-arm randomized controlled trial

“…On the other hand, explanations for the adverse effects observed among customers from non-deprived areas remain speculative. One study on an information nudge did not show moderating effects by SEP [ 22 ], while others indicated that groups with a higher SEP can show reactance following social norms and/or information nudges [ 36 ] and likely prefer to maintain autonomous choices [ 37 ]. Also, higher levels of health-consciousness could result in more deliberate food choices, instead of relying on automatic product choices [ 3 ], i.e., it may be customers with a higher SEP who experienced the information nudges as patronizing, threatening their autonomy, causing them to reject nudged products.…”

“…Based on an implementation duration of five weeks, we expected to collect data from ~ 5500 shoppers per trial arm. As simulated experimental studies on online nudging strategies relied on much smaller samples (e.g., ranging from 218 up to 476 per intervention arm [ 17 , 18 , 22 ]), we were confident to have secured adequate power for the analyses and considered a corresponding sample size calculation unnecessary.…”

“…Nowadays, online grocery services are increasingly popular and offer opportunities for supermarkets to promote healthier food purchases on a large scale and at relatively low costs. Tentative evidence suggests that information nudges [ 7 – 16 ], placement nudges [ 17 – 21 ], or a combination of placement and availability nudges [ 22 ], are efficacious in promoting healthier purchases in an online supermarket setting. Only one study, testing healthier swap suggestions via online pop-ups, did not report beneficial effects on purchasing behaviors [ 23 ].…”

Socioeconomic position, energy labelling and portion size selection: An online study comparing calorie and physical activity calorie equivalent (PACE) labelling in UK adults

“…Because lower SEP is associated with reduced executive function and being less motivated by health when making food choices ( Kao, Nayak, Doan, & Tarullo, 2018 ; Pechey, Monsivais, Ng, & Marteau, 2015 ), energy labelling may have a smaller effect on portion size selections in people of lower vs. higher SEP. However, some recent studies have not supported this hypothesis ( Marty, Cook, Piernas, Jebb, & Robinson, 2020 , Marty, Jones, & Robinson, 2020 , Marty, Reed, Jones, & Robinson, 2021 , Robinson, Smith, & Jones, 2021 ). In the present study, we therefore examined whether any effects of energy labelling (kcal or PACE) on portion size selection were moderated by SEP and explored whether SEP differences in executive function or food choice motives explained any differential effects of energy labelling on portion size selection by SEP. We hypothesised that effects of energy labelling may be smaller in lower SEP participants compared to higher SEP participants and this may be explained by SEP differences in executive functioning and health motives.…”