Psychological Well-Being and Dysfunctional Eating Styles as Key Moderators of Sustainable Eating Behaviors: Mind the Gap Between Intention and Action

Background: Promoting sustainable eating is gaining increasing attention, yet the transition from intentions to actual behaviors remains unclear. This study compares the theory of planned behavior (TPB) and the theory of behavioral choice (TBC) in predicting such intentions and examines the moderating role of distress, psychological well-being, and dysfunctional eating styles in the intention–behavior relationship. Methods: A total of 223 participants from the general population (29.49 ± 9.30 years; 68.6% females) completed an online survey assessing TPB and TBC predictors, the Sustainable and Healthy Dietary Behaviors (SHDB) questionnaire, the Depression and Anxiety Stress Scale (DASS-21), the Psychological Well-Being Scale (PWBS), and the Dutch Eating Behavior Questionnaire (DEBQ). Results: The TBC model explained a significantly greater variance in intention (R2 = 0.45, ΔR2 = 0.28, F(215,4) = 27.27, p < 0.001) compared to the TPB, with TBC-affect (β = 0.48, p < 0.001) and felt obligation (β = 0.23, p < 0.001) being the strongest predictors. Moderation analyses revealed that the intention–behavior link was stronger in participants with lower external eating and autonomy. Conclusions: Both internal and external factors play a crucial role in predicting intentions. In addition, the intention–behavior link is stronger in individuals who are less reactive to external food stimuli and more influenced by social pressure. Promoting more balanced psychological well-being and functional eating habits may foster more sustainable diets.