Mind the Gap? An Intensive Longitudinal Study of Between-Person and Within-Person Intention-Behavior Relations

Background: Despite their good intentions, people often do not eat healthily. This is known as the intention-behavior gap. Although the intention-behavior relationship is theorized as a within-person process, most evidence is based on between-person differences. Purpose: The purpose of the present study is to investigate the within-person intention-behavior association for unhealthy snack consumption. Methods: Young adults (N = 45) participated in an intensive longitudinal study. They reported intentions and snack consumption five times daily for 7 days (n = 1068 observations analyzed). Results: A within-person unit difference in intentions was associated with a halving of the number of unhealthy snacks consumed in the following 3 h (CI₉₅ 27–70 %). Between-person differences in average intentions did not predict unhealthy snack consumption. Conclusions: Consistent with theory, the intention-behavior relation for healthy eating is best understood as a within-person process. Interventions to reduce unhealthy snacking should target times of day when intentions are weakest.