Purpose: Intention and planning are important predictors of dietary change. However, little attention has been given yet to the relationship between them as a function of other social-cognitive factors and their interplay with socio-demographics such as sex.
Methods: In an observational study (1520 women, 430 men) with two measurement points in time, intention (predictor), planning (mediator), social support (first moderator), and sex (second moderator) were assessed to predict changes in diet separately for fruit and vegetable intake.
Results: All predictors had a main effect on fruit intake but no interactions emerged. For vegetable intake, the mediation-chain was qualified by a three-way interaction: for women, the lower the perceived social support, the more the translation of planning into behavior; for men, the higher the perceived social support, the more the translation of planning into behavior.
Conclusions: Even though intention and planning are predictors of dietary change, they operate differently under specific conditions (level of social support), for specific subgroups (men vs. women), and for different target behaviors (fruit vs. vegetable intake). These results suggest to further examine the mechanisms by which intentions are translated into behavior via planning.
Keywords: Fruit and vegetable intake; Intention; Planning; Sex differences; Social support.