Randomized trial of planning tools to reduce unhealthy snacking: Implications for health literacy

Guidance to address health literacy often focuses on health education rather than tools to facilitate action, despite action being important for self-management. This study evaluated an online intervention informed by health literate design principles and behavior change theory to reduce unhealthy snacking. 440 participants were recruited online and randomized to an intervention: 1) Health-literate action plan (guided implementation intention); 2) Standard action plan (self-guided implementation intention); 3) Education (healthy snacking fact-sheet). The primary outcome was self-reported unhealthy snacking. Follow-up was at 1 month. 373 participants (84.8%) completed follow-up. Half the sample had adequate health literacy (52%), and the other half had low (24%) or possibly low (25%) health literacy, as measured by Newest Vital Sign (NVS). At follow-up, lower health literacy was associated with more unhealthy snacks and there was no overall difference between intervention groups. However, participants with lower health literacy who used the health-literate action plan reported less unhealthy snacking compared to the standard action plan; the reverse was true for those with higher health literacy scores (b = 1.7, p = 0.03). People scoring 2 points below the mean NVS (M = 3.4, SD = 2.0) using the health-literate action plan reported eating 8 fewer serves of unhealthy snacks, whereas people scoring 2 points above the mean NVS reported eating 6 more serves of unhealthy snacks using the same tool. These findings suggest that the universal precautions approach currently recommended for health information may be less effective for facilitating action than tailoring to health literacy level. ANZCTR identifier: ACTRN12617001194358.