Augmenting fruit and vegetable consumption by an online intervention: psychological mechanisms


  • J. Keller
  • S. Motter
  • M. Motter
  • R. Schwarzer


Background: Fruit and vegetable (FV) intake is examined among men and women who participated in an online intervention. The main purpose of the analyses regards the role of psychological mechanisms that might be responsible for individual differences in the process of behavior change. The psychological constructs involved are outcome expectancies, motivation, planning, and self-efficacy. The secondary purpose of the analyses is the evaluation of a self-efficacy treatment component. Methods: A two-arm online intervention focusing on FV planning was conducted to improve FV intake with follow-ups at two and four weeks. The only difference between the standard and the enhanced intervention group was the additional inclusion of a self-efficacy ingredient in the latter. Participants were N=275 adults of whom n=148 completed the four-week follow-up. Their age range was 18 to 81 years (M=32.5, SD=14). Data were analyzed using linear mixed models and longitudinal structural equation models. Findings: Analyses yielded an overall increase in self-reported FV intake. Moreover, a triple interaction between time, sex, and experimental groups on self-efficacy emerged, indicating that men reported an increase in FV self-efficacy independent of groups, whereas women in the enhanced group developed higher FV self-efficacy. Planning, self-efficacy, and motivation mediated between outcome expectancies, and follow-up FV intake. Discussion: Both intervention arms produced overall improvements in self-reported FV intake. The mediation sequence leading from initial outcome expectancies via planning, self-efficacy, and motivation towards final FV intake underlined the importance to include psychological strategies such as planning and self-efficacy in (online) interventions on FV intake.





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