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.

Translating intentions into nutrition behaviors via planning requires self-efficacy: evidence from Thailand and Germany.

A first step towards the improvement of daily dietary behaviors is forming an intention to change one's nutrition. However, an intention by itself is not sufficient for successful action. Rather, to translate intentions into behavior, careful planning is recommended. Thus, planning constitutes a mediator between the intention and the behavior. However, if a person lacks self-efficacy, this mediation might fail. Previous research in Costa Rica and South Korea has identified perceived self-efficacy as a moderator of the intention-planning-behavior relationship. To examine further the moderator role of self-efficacy, two additional studies were designed in Thailand and Germany. Study 1 surveyed 1718 Thai university students in terms of a low-fat diet; Study 2 surveyed 1140 German internet users in terms of their fruit and vegetable consumption at two measurement points in time, 6 months apart. Intentions served as predictor, planning as mediator, self-efficacy as moderator, and behaviors as outcomes. First, intentions were translated into nutrition behaviors by planning. Second, self-efficacy moderated this mediation in both studies: The strength of the mediated effect increased along with levels of self-efficacy, even when accounting for baseline behaviors. For planning to mediate the intention-behavior relation, people must not harbor self-doubts. If they lack self-efficacy, intentions are not well translated into nutrition behavior through planning.