What helps to form a healthy nutrition habit? Daily associations of intrinsic reward, anticipated regret, and self-efficacy with automaticity

High automaticity in healthy nutrition behaviors is related to long-term maintenance of these behaviors. Drawing upon theoretical frameworks of habit formation, proposed antecedents such as intrinsic reward, anticipated regret, and self-efficacy are important correlates of automaticity, but not much is known about their day-by-day relationships with automaticity in healthy nutrition behaviors. This study tested previous-day within-person (i.e., from one day to the next) and same-day within-person associations of intrinsic reward, anticipated regret, and self-efficacy with automaticity of a healthy nutrition behavior, for which participants attempted to form a new habit.Secondary analyses of a randomized controlled trial with two planning intervention conditions including a longitudinal sample of n = 135 participants (age: M = 24.82 years; SD = 7.27) are reported. Participants formed a plan on a self-selected healthy nutrition behavior to become a new habit and were followed up over 12 weeks assessing daily levels of plan-specific intrinsic reward, anticipated regret, self-efficacy, and automaticity. Lagged multilevel models with 84 study days nested in participants estimated previous-day within-person, same-day within-person, and between-person relationships of intrinsic reward, anticipated regret, and self-efficacy with automaticity.Regarding within-level relationships, higher-than-usual levels of intrinsic reward, anticipated regret, and self-efficacy of the same day but not of the previous day were associated with higher within-person automaticity. With respect to between-level relationships, higher between-levels (i.e., higher person mean levels across the study period) of intrinsic reward, anticipated regret, and self-efficacy were linked with higher automaticity.Findings point towards the potential to intervene on intrinsic reward, anticipated regret, and self-efficacy when aiming to promote a new healthy nutrition habit.