Which Healthy Eating Nudges Work Best? A Meta-Analysis of Field Experiments
Résumé
We examine the effectiveness in field settings of seven healthy eating nudges, classified according to whether they are 1) cognitively-oriented, such as “descriptive nutritional labeling,” “evaluative nutritional labeling,” or “visibility enhancements”; 2) affectively-oriented, such as “hedonic enhancements or “healthy eating calls”; or 3) behaviorally-oriented, such as “convenience enhancements” or “size enhancements.” Our multivariate three-level meta-analysis of 299 effect sizes, controlling for eating behavior, population, and study characteristics, yields a standardized mean difference (Cohen’s d) of .23 (equivalent to -124 kcal/day). Effect sizes increase as the focus of the nudges shifts from cognition (d=.12, -64 kcal) to affect (d=.24, -129 kcal) to behavior (d=.39, -209 kcal). Interventions are more effective at reducing unhealthy eating than increasing healthy eating or reducing total eating. Effect sizes are larger in the US than in other countries; in restaurants or cafeterias than in grocery stores; and in studies including a control group. Effect sizes are similar for food selection vs. consumption, for children vs. adults, and are independent of study duration. Compared to the typical nudge study (d=.12), one implementing the best nudge scenario can expect a six-fold increase in effectiveness (to d=.74), with half due to switching from cognitively-oriented to behaviorally-oriented nudges.