Planning and self-efficacy can increase fruit and vegetable consumption: a randomized controlled trial.

Fruit and vegetable consumption represents a nutritional goal to prevent obesity and chronic illness. To change dietary behaviors, people must be motivated to do so, and they must translate their motivation into actual behavior. The present experiment aims at the psychological mechanisms that support such changes, with a particular focus on dietary self-efficacy and planning skills. A randomized controlled trial compared a theory-based psychological intervention with a health education session in 114 participants. Dependent variables were fruit and vegetable consumption, intention to consume more fruit and vegetables, planning to consume more, and dietary self-efficacy, assessed before the intervention, 1 week afterwards, and at 6-week follow up. Significant group by time interactions for all four dependent variables documented superior treatment effects for the psychological intervention group, with substantially higher scores at posttest and follow-up for the experimental group, although all students benefited from participation. To identify the contribution of the main intervention ingredients (self-efficacy and planning), regression analyses yielded mediator effects for these two factors. A social-cognitive intervention to improve fruit and vegetable consumption was superior to a knowledge-based education session. Self-efficacy and planning seem to play a major role in the mechanisms that facilitate dietary changes.