Background: Following successful use in tobacco control, health warnings on energy-dense, nutrient-poor foods and beverages have been proposed as a potential anti-obesity intervention.
Aim: To investigate the efficacy of health warnings in promoting healthy dietary choices, and examine how health warning design factors (positive versus negative message framing, text-only versus text-and-graphic warnings) influence their efficacy.
Methods: A mixed-effects experimental design was used, whereby 96 participants completed a novel dietary self-control priming task. Participants were randomly assigned to one of five health warning groups featuring the following health warnings formats: text-based with negatively framed messages (TN; n=16), graphic with negative framing (GN; n=16), text with positive framing (TP; n=16), graphic with positive framing (GP; n=16) and a message-free control group (C; n=32). Participants initially provided subjective health and taste ratings of snack food items. Participants were then required to choose items to consume at the end of the experiment prior to- and post- exposure to health warning messages. A measure of dietary self-control (DSC) was calculated based on the provided health and taste ratings. Linear mixed effects modelling was used to test the influence of health warning characteristics on DSC, while controlling for participant and stimulus related variance.
Results: A significant interaction effect between health warning group and decision stage condition (pre- and post- priming with health warning images) on DSC was found (p < .001). GN participants displayed significantly greater DSC than all other groups, while TN and GP participants showed greater DSC than TP and C participants, which did not differ.
Conclusions: Health warnings primed healthier dietary decision making and may be effective in reducing obesity. Negatively framed health warnings were more effective than positively framed health warnings, and graphic warnings promoted greater DSC than purely text-based health warnings.