Sustainable dietary choices improved by reflection before a nudge in an online experiment

Current food choices have a high carbon footprint and are incompatible with climate goals. Transitioning to more environmentally friendly diets is therefore important. Behavioural 'nudges' have been widely used to reduce meat-based food demand, subtly altering choice presentation without banning or raising costs. However, scaling up nudges has proven challenging, sometimes raising ethical concerns. To address this, behavioural science proposes empowering individuals to reflect on their choices, fostering meaningful and more environmentally-friendly behavioural changes. In an experimental study with 3,074 UK participants, we compared three agency-enhancing tools ('boost', 'think' and 'nudge+') with classic nudges (opt-out default and labelling) to promote sustainable dietary intentions. All behavioural interventions increased intentions for sustainable foods but encouraging reflection on dietary preferences before defaulting people into greener diets yielded the best results. Adding a pledge before the default nudge, as in nudge+ (pledge+ default), additionally reduced emissions from intended orders of meals by 40%. Our research suggests that food companies can enhance their sustainability efforts by prompting customers to think before nudging them into consuming more sustainable food.