Nudging is increasingly used in public health interventions in Western societies to produced health-promoting behavior changes; however, there is lack of clarity as to what constitutes a nudge, scant knowledge of the effectiveness of nudging techniques in public health lifestyle interventions and a number of ethical and value-based concerns. The aim of this review is to address these research lacunae and identify the characteristics of nudges in empirical research on public health interventions intended to induce healthy lifestyle changes, including whether they are effective. We conducted systematic searches for relevant articles published between January 2008 and April 2019 in three databases, PubMed, CINAHL and PsycINFO, and combined this with a metasynthesis to construct interpretative explanations. A total of 66 original studies met the inclusion criteria. The findings of the systematic review showed that most nudging interventions involved diet/nutrition, most were carried out as single experiments, and the majority had the intended effects. Specific nudging techniques were identified with respect to the broader nudging categories of accessibility, presentation, using messages and pictures, technology-supported information, financial incentives, affecting the senses, and cognitive loading; several studies included more than one nudging technique. Although many nudging techniques had the intended effects, it is unclear whether they would work outside the study setting. The synthesis revealed that the studies lacked critical reflection on the assumptions about health that were implicit in nudging interventions, the cultural acceptability of nudges, the context-free assumptions of nudging theory, and the implications of these aspects for the public health context.

Summary Nudging has been discussed in the context of public health, and ethical issues raised by nudging in public health contexts have been highlighted. In this article, we first identify types of nudging approaches and techniques that have been used in screening programmes, and ethical issues that have been associated with nudging: paternalism, limited autonomy and manipulation. We then identify nudging techniques used in a pamphlet developed for the Danish National Screening Program for Colorectal Cancer. These include framing, default nudge, use of hassle bias, authority nudge and priming. The pamphlet and the very offering of a screening programme can in themselves be considered nudges. Whether nudging strategies are ethically problematic depend on whether they are categorized as educative- or non-educative nudges. Educative nudges seek to affect people’s choice making by engaging their reflective capabilities. Non-educative nudges work by circumventing people’s reflective capabilities. Information materials are, on the face of it, meant to engage citizens’ reflective capacities. Recipients are likely to receive information materials with this expectation, and thus not expect to be affected in other ways. Non-educative nudges may therefore be particularly problematic in the context of information on screening, also as participating in screening does not always benefit the individual.

Background The concept of nudging has been imported from behavioral economics into the public health context to correct 'unhealthy behaviours' and produce health-promoting behavior changes in individuals. However, there is lack of clarity as to what constitutes a nudge and whether nudging techniques in public health lifestyle interventions are effective. The aim of this literature review is to identify nudging techniques used in public health lifestyle interventions and to investigate whether nudging techniques induce expected healthy lifestyle changes in interventions that relate to diet, exercise, sleep, alcohol and smoking. Methods A systematic literature review on the concept “nudging” in public health lifestyle interventions was conducted, applying a free text search strategy on a set of search terms in three databases: PubMed, CINAHL and PsycINFO. Articles meeting the inclusion criteria were included in our data set, and we performed a meta-synthesis to construct interpretative explanations. Results 66 original studies published in international peer-reviewed journals were identified. The findings showed that most nudging interventions involved diet/nutrition (n = 55), were carried out as single experiments, lasted for a short period of time and that the majority had the intended effects. Specific nudging techniques were identified and sorted into eight broader categories. The most commonly used nudging technique involved making healthier food items more apparent and accessible than less healthy foods. Conclusions The synthesis showed that these studies were limited with regard to their design, target groups, duration of the intervention, measures of effectiveness and critical reflection on ethical issues. Key messages Nudging may be effective in producing immediate behavioral changes; however, there is little evidence that nudging interventions result in lasting behavioral changes outside the setting of the studies. Further critical discussions about the implications of nudging in public health lifestyles intervention are required.