Nudging food choice in a prison setting: an investigation using food choice data

Background: The prison population presents complex health needs and is disproportionately affected by poor health, compared to the general population. Diet has a clear role in prisoner health, and the prison food environment within which food choices are made is relatively under-researched. The aim of this study was to examine whether food choices in a women's prison changed after the introduction of a new menu design by the catering team.Methods: The adjusted menu design incorporated an emoticon (a smiley face) placed next to designated 'Healthy Choice' foods on the menu sheets, which were used to preselect meals. Data comprised all women's (n = 865) food choices (more than 115,000 selections) for a period of 8 weeks (with the new menu) as well as 8 weeks prior (baseline period). The study design was a pre-post intervention study, and food selection was examined using chi-square tests and binary logistic regression models.Results: The selection of promoted foods overall significantly increased under the new menu design (with the emoticon nudge strategy) compared to baseline; the effect size, however, was small according to the usual guidelines (21.4% compared to 20% at baseline; chi(2)(1) = 32.6, p < 0.001, phi = 0.02). Individuals were 11% more likely (p < 0.001) to select the promoted 'Healthy Choice' foods under the adjusted food choice architecture. A significant effect was found for lunch and evening meal - but not for desserts. A minority of individual food items that were promoted had significant positive changes in selection, and were 1.3-4 times as likely to be selected when emoticons had been introduced, compared to baseline.Conclusions: Further research is needed to examine the potential added benefit of multiple complementary nudge strategies, and the relevance of the preselection of foods in advance of consumption.