A quantitative test of the face validity of behavior-change messages based on the Brazilian Dietary Guidelines

Implementation science has scant evidence of how dietary guidelines can be developed into actionable behavior-change messages and even less evidence on their motivating potential and perceived effect on behavior. This may explain the widening gap between nutrition science and individual behavior and the low uptake of dietary recommendations by the population for which they are intended. This study aimed to: (i) assess participant receptivity and acceptance of behavior-change messages; (ii) determine if the behavior-change strategies used in the messages and the main theme they relayed influenced participant evaluation of the messages; (iii) explore if evaluations varied by participants' stage of behavior-change; and (iv) elucidate reasons for non-compliance with the messages.

An online survey was used to test the face validity and participant receptivity of 28 behavior-change messages, among a diverse sample of 2400 adult Brazilians. Participants' understanding of the messages, message likeability and convincingness, and the probability that participants would change behavior in accordance with the message were measured, along with reasons for non-compliance.

The mean overall scores suggested that participants liked the messages, understood them, and found them convincing. As expected, the probability of complying with the messages scored lower compared to other study outcomes. Messages about shopping practices, cooking practices, and planning and organization performed better than those on other themes. Participants were more receptive to messages that included behavior-change strategies like goals, social identity, and pleasure, however, the probability of compliance was higher for messages with constructs that emphasized health and cost consequences. Participants trying to change their diet or seeking resources to support healthier dietary choices had greater engagement with and receptivity to the messages. Time and effort, and high costs associated with making healthy changes, were barriers to compliance.

Messages may help improve individual understanding, stimulate interest in a topic and get participants engaged, particularly if messages are goal-oriented and highlight the pleasure and collective identity of these food-related behaviors. However, messages stop short of addressing the structural, social, and economic barriers to healthy diets. These aspects will need to be targeted through legislative action for sustainable behavior change.