A systematic review and meta-analysis on the effectiveness of if-then plans – in a strict sense – to facilitate fruit and vegetable consumption in adults

BACKGROUND: A fruit-and-vegetable rich diet is important in the prevention of non-communicable diseases. If-then plans, or implementation intentions, are proposed to facilitate behavior change by formulating plans that link perceivable cues and goal-directed responses. We investigated the effectiveness of if-then planning interventions to facilitate fruit and vegetable intake in adults, with a strict focus on if-then planning procedures and excluded procedures representing conventional planning. METHODS: A systematic review (MEDLINE, Embase, and PsycInfo; last searched April 3rd, 2025) and meta-analysis was conducted. Included studies were randomized controlled trials, testing the effect of if-then plans on fruit and/or vegetable intake against active control groups. RESULTS: Ten articles were identified as eligible, including 12 comparisons (N = 2399) with intervention-outcome periods of 1 week to 24 months. If-then planning participants reported consuming approximately a quarter of a portion of fruit and vegetable per day more than participants in the control groups (MD = 0.29, 95% CI: 0.11; 0.48). CONCLUSION: A central limitation of the analysis is that all included studies are based on self-reported fruit and vegetable consumption. While the effect size of the investigated intervention is small, its low resource requirements make it an accessible option for promoting fruit and vegetable consumption.