Evaluating nudge and boost strategies for greener meals in food-delivery: An experimental study

Global food systems are responsible for approximately 30% of global greenhouse gas emissions, making a shift toward lower-carbon diets essential for mitigating climate change. While nudges have shown efficacy in steering food choices, concerns persist regarding individuals' autonomy, transparency and the durability of behavioural change. As an alternative, boosts seek to enhance consumers' competencies and support informed decision-making. However, there is a dearth of comparative research on nudges versus boosts, particularly regarding their ability to foster a sense of consumer responsibility for sustainable consumption (CRSC) - an important driver of long-term behavioural change. To address this gap, this study evaluates a "default+" nudge and an "information+" boost within a simulated food-delivery environment, while examining CRSC as a potential mediator. Employing a mixed design experiment (2 survey waves: intervention, follow-up; 3 conditions: nudge, boost, control), we collected data from 664 German consumers. Our primary outcome was the estimated CO₂ footprint of participants' hypothetical meal choices, calculated using established secondary emission data. Results show that the nudge intervention significantly reduced participants' meal-related CO₂ emissions, whereas the boost intervention yielded considerably smaller and less consistent effects. However, neither intervention produced lasting effects in the follow-up survey, where choice architecture reverted to the control condition. Moreover, while higher CRSC induced lower emissions, neither the nudge nor the boost elevated CRSC, and thus the hypothesized mediating role of consumer responsibility was not supported. We discuss the theoretical and practical implications of these results for the design of effective sustainable food choice interventions.