Stadler, G., Oettingen, G., & Gollwitzer, P. M. (2010). Intervention effects of information and self-regulation on eating fruits and vegetables over two years. Health Psychology, 29, 274-283.
Objective: This study tested whether an intervention that combined information with self-regulation strategies had a better effect on eating fruits and vegetables than an information-only intervention. Design: Women between age 30 and 50 (N=255) participated in a 24-month randomized controlled trial comparing two brief interventions: All participants received the same information intervention; participants in the information plus self-regulation group additionally learned a self-regulation technique that integrates mental contrasting with implementation intentions. Main outcome measures: Participants reported in daily diaries how many servings of fruits and vegetables they ate per day during 1 week at baseline, and in the first week, 1, 2, 4, and 24 months after intervention. Results: Participants in both groups ate more fruits and vegetables (0.47 to 1.00 daily servings) than at baseline during the first 4 months after intervention. Two years later, participants in the information plus self-regulation group maintained the higher intake, whereas participants in the information group returned to baseline levels. Conclusion: Adding self-regulation training to an information intervention increased its effectiveness for long-term behavior change.