Background: Non-sustainable diets are associated with several environmental and health-related problems. Psychology research is interested in the study of food choice determinants, and several theoretical frameworks have been applied to study mechanisms underlying behavioral change and to develop theory-based interventions. The present systematic review is aimed at reviewing the existing literature on the psychological theoretical frameworks used to study sustainable and/or healthy food choices and their application for the development of interventions promoting such food choices, both in general and clinical populations. Methods: A systematic search of PubMed, PsycInfo, and Scopus was conducted according to PRISMA criteria. Results: Forty-five articles met the inclusion criteria and thirty-five theoretical frameworks emerged, mostly pertaining to social psychology and with the most widely used being the Theory of Planned Behavior. The majority of studies had a cross-sectional design, were conducted in general populations, and focused on healthy food choices. Only a few studies tested theory-based interventions. Internal (i.e., self-efficacy, personal values, and motivation) and external (i.e., peers, family, and social media influence) factors emerged as relevant healthy and sustainable eating determinants. Conclusions: The current review underlines that an integrative perspective combining prompts from different psychology fields is needed in order to identify the psychological factors influencing food choices and to develop psychological interventions for the promotion of more sustainable diets.

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.