How eating-related social media postings influence healthy eating in senders and network members: two field experiments with intensive longitudinal data

Young adults are frequently confronted with eating-related social media content. How such exposure influences eating in those who post and their network members is largely unknown. We conducted two intensive longitudinal field experiments combining self-reports with social media data. The posting behavior of young adults was manipulated. We examined how postings about fruit and vegetables affected intake in senders and their network members (Study 1, N = 81) and in senders with a change goal (Study 2, N = 128). Potential mechanisms of action were explored. Descriptively, posting led to a stronger increase of senders' and network members' intake, but this increase was not statistically significant. Posting led to higher perceived social support and injunctive norms of senders (Study 1). Posting supported eating behavior change; the effect size was comparable to picture-based self-monitoring of intake (Study 2). Intraindividual variations in senders’ daily eating-related social media activities were associated with daily eating behavior and perceived social support (both studies), daily self-efficacy, experiential and instrumental attitudes, and goal commitment (Study 2). Our studies underline that social media environments should be considered in research and interventions targeting eating behavior of young adults.