Review: Nudge interventions to promote healthy diets and physical activity

•Evidence on “nudge” interventions on diet and physical activity is limited.•The stand-alone use of “nudge” interventions remains ambiguous.•How attributes of “nudge” interventions mediate efficacy requires further research.•Conceptual development, rigorous larger studies and better reporting are needed. “Nudge” policies are increasingly popular, seeking to modify health-related decisions by affecting response to available options. Thus, critical appraisals of the effectiveness of health-related nudging interventions could help health policy makers in making evidence-based decisions with regards to which of these interventions should be incorporated into policy. The aim of the present effort was to systematically appraise the evidence on nudging interventions on healthy diet and physical activity (PA). A systematic review was performed using Pubmed, Web of Science Core Collection citation index and the Cochrane Controlled Register of Trials (CENTRAL). Interventional studies were included if they quantitatively assessed healthy diet and/or PA interventions that were explicitly related to a nudging context. Methodological assessment was performed using the Cochrane collaboration’s risk of bias tool and the Research Triangle Institute item bank. Sixty-four studies were included with varying degrees of bias. Sixty studies investigated healthy diet interventions, three studied PA interventions and one studied interventions pertaining to both. Overall, specific types of interventions such as proximity and presentation alterations can be effective in encouraging people towards the adoption of healthier diet choices, whereas labelling, availability, prompting, functional design and sizing “nudge” interventions provide inconclusive results so far. Nudging interventions improving convenience seem to be effective in encouraging people towards making healthier diet choices, whereas evidence on PA is limited. Further conceptual development and research is needed to optimally determine the type, intensity and circumstances that make nudge-related interventions more effective, particularly regarding PA.