Objective: The current study tested whether self-affirmation in the context of a threatening health message helps promote a health behavior (fruit and vegetable consumption) over a 3-month period, and whether adding a manipulation to support the translation of intentions into behavior (an implementation intentions induction) enhances the impact of self-affirmation.
Methods: Participants (N = 332, 71% women) reported their baseline consumption and were randomly assigned to condition in a 2 (self-affirmation: yes, no) × 2 (implementation intentions: formed, not formed) between-subjects factorial design. They completed a self-affirmation/control task and then read a health communication advising eating at least 5 portions of fruit and vegetables daily. Next participants reported intentions for behavior change, after which they formed/did not form relevant implementation intentions. Consumption was measured again 7 days and 3 months postintervention.
Results: Self-affirmed (vs. nonaffirmed) participants reported eating more fruit and vegetables at both follow-ups. Forming (vs. not forming) implementation intentions was also beneficial for consumption. At 7 days, there was also a significant self-affirmation × implementation intentions interaction: consumption was highest when self-affirmed participants also formed implementation intentions.
Conclusions: The present study offers new evidence concerning the impact and durability of self-affirmation on health behaviors and the role of implementation intentions in enhancing the impact of self-affirmation.