Which Healthy Eating Nudges Work Best? A Meta-Analysis of Field Experiments

We examine the effectiveness in field settings of seven healthy eating nudges, classified according to whether they influence 1) cognition, via “descriptive nutritional labeling,” “evaluative nutritional labeling,” or “salience enhancements”; 2) affect, via “hedonic or sensory cues” or “healthy eating prods”; or 3) behavior, via “convenience enhancements” or “plate and portion size changes.” Compared with existing univariate meta-analyses, our multivariate three-level meta-analysis of 277 effect sizes controlling for eating behavior, population, and study characteristics yields smaller effect sizes overall. These effect sizes increase as the focus of the intervention shifts from cognition (d=.08, equivalent to -45 kcal/day) to affect (d=.22, -121 kcal) to behavior (d=.35, -186 kcal). Interventions are more effective at reducing unhealthy eating than at 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 study, one testing the best nudge scenario should expect a fourfold increase in effectiveness, with half due to switching from cognitive to behavioral nudges.