Plans Not Needed if You Have High and Stable Self-Efficacy: Planning Intervention and Snack Intake in the Context of Self-Efficacy Trajectories Forming action plans is expected to move people from intention to action. We hypothesized that the effects of planning interventions may depend on changes in self-efficacy beliefs. Participants were assigned to the control or the planning intervention groups and reported their self-efficacy, sweet and salty snack intake at the baseline and four months later. The results suggest that an increase (...) of efficacy beliefs over time augmented the effects of the planning intervention and resulted in the lowest snack intake. Planning intervention also prompted lower unhealthy snacking if efficacy beliefs were decreasing. Those who have stable-high self-efficacy were able to achieve low snack intake regardless of the group assignment. (shrink)