Nudging plant-based alternatives to meat and dairy in a real-life online supermarket: A randomized controlled trial.

A shift from predominantly animal-based to plant-based consumption can benefit both planetary and public health. Nudging may help to promote such a shift. This study investigated nudge effects on plant-based alternatives to meat and dairy in an online supermarket. We conducted a two-arm, parallel-group, randomized controlled real-life online supermarket trial. Each customer transaction was randomized to a control arm (regular online supermarket) or an intervention arm (addition of placement, hedonic property and dynamic social norm nudges promoting meat and dairy alternatives). Outcomes were the aggregate of meat and dairy alternative purchases (primary outcome), the number of meat purchases, dairy purchases, meat alternative purchases, and dairy alternative purchases (secondary), and retailer revenue (tertiary). Generalized linear mixed models with a Conway-Maxwell Poisson distribution were used to estimate incidence rate ratios (IRRs). Analyzed data included 8488 transactions by participants (n = 4,266 control arm, n = 4,222 intervention arm), out of which 2,411 (66%) were aged above 45 years, 5,660 (67%) were females, and 1,970 (23%) lived in socially disadvantaged neighborhoods. Intervention arm participants purchased 10% (IRR 1.10 (95% CI 0.99-1.23)) more meat and dairy alternatives and 16% (1.16 (0.99-1.36)) more meat alternatives than control arm participants, although these findings are not statistically significant. There was no difference in dairy alternative purchases (1.00 (0.90-1.10)). Intervention arm participants purchased 3% less meats (0.97 (0.93-1.02)) and 2% less dairy products (0.98 (0.95-1.02)) than control participants. Retailer revenue was not affected (0.98 (0.95-1.01)). Online nudging strategies alone did not lead to a statistically significant higher amount of plant-based purchases, but replication of this work is needed with increased study power. Future studies should also consider nudging strategies as part of a broader set of policies to promote plant-based purchases. TRIAL REGISTRATION: Prospectively registered on 14th of May 2022. ISRCTN16569242 (https://doi.org/10.1186/ISRCTN16569242).

How perceptions of meat consumption norms differ across contexts and meat consumer groups.

Social norm perceptions are implicit standards describing what is typically done or seen as acceptable and have shown to be important both in sustaining meat consumption as well as facilitating meat reduction. Norm perceptions depend on individual differences and the contexts (e.g., supermarket, restaurant). Yet, evidence how norm perceptions differ within and across individuals is scarce. The primary aim of this study was to investigate how descriptive, injunctive, and personal norms perceptions favouring meat consumption differ across contexts and meat consumer groups. The second aim was to investigate how generic dynamic norm perceptions vary across meat consumer groups. British meat eaters (n = 1205, 25-65 years) participated in an online cross-sectional survey. Weekly meat, fish and meat substitute consumption was measured with the adapted Oxford Meat Frequency Questionnaire. All but dynamic norm perceptions were measured for the supermarket, restaurant and worksite cafeteria context. Dynamic norms were measured without a specified context. A two-step cluster analysis was conducted to identify meat consumer groups. Descriptive norm perceptions favouring meat consumption were strongest in supermarket and restaurant contexts, compared to the worksite cafeteria. Injunctive and personal norms favouring meat consumption were both perceived strongest in the supermarket, followed by the restaurant, and least in the worksite cafeteria context. Four meat consumer groups were identified and those with higher meat intake (i.e., Meat lovers and Exceeders) perceived norms favouring meat consumption stronger and norms favouring meat avoidance weaker than the groups with lower meat intake (i.e., Flexitarians and Moderates). While norm perceptions differed between meat consumer groups, the pattern of contextual differences is similar for these meat consumer groups. Our findings underscore the importance of considering contexts and meat consumer groups in efforts to reduce meat consumption.

Experts' perceptions on motivators and barriers of healthy and sustainable dietary behaviors among adolescents: The SWITCH project.

The interplay of influences shaping dietary behaviors of adolescents needs to be well-understood to develop effective strategies stimulating healthy and sustainable behaviors. This study aimed to identify the most relevant, urgent, changeable and effective motivators and barriers of healthy and sustainable dietary behaviors among adolescents (10-19 years), as perceived by an inter- and transdisciplinary expert panel. Experts working in practice (N = 19) and academia (N = 13) - in the field of sustainability, health, nutrition and/or education - participated in this exploratory mixed-methods study. Five online semi-structured focus groups were conducted (6-7 participants). Data was thematically analyzed by two coders independently, using the socioecological framework. Subsequently, the same experts individually selected the five most relevant determinants and rated those on their urgency, changeability and effectiveness through an online questionnaire (N = 21). Participants revealed a wide system of 31 main determinants including 173 sub-determinants that motivate or hinder healthy and sustainable eating among adolescents. This system of determinants was mapped on the different layers of the socioecological model: individual factors (25 motivators; 30 barriers), social environments (15 motivators; 13 barriers), physical environments (18 motivators; 15 barriers), macro-level environments (19 motivators; 38 barriers). 'Role of peers' (social environment) was selected most as a determinant to be targeted in interventions (N = 13; urgency (M = 6.38) changeability (M = 3.85), effectiveness (M = 5.62)), followed by 'food environment around school' (N = 9; urgency (M = 5.78) changeability (M = 3.44), effectiveness (M = 5.44)), 'social influences' (N = 7; urgency (M = 5.43) changeability (M = 4.00), effectiveness (M = 5.71)), 'autonomy in development' (N = 7; urgency (M = 6.00) changeability (M = 4.29), effectiveness (M = 5.86)) and 'food availability' (N = 7; urgency (M = 6.29) changeability (M = 3.29), effectiveness (M = 6.29)). The prioritized determinants indicate that adolescents should be provided more supportive social and physical environments that promote healthy and sustainable dietary behaviors, taking into account their growing autonomy.