Why we waste: A meta-analysis of food waste behavior using the Theory of Planned Behavior (TPB)

The Theory of Planned Behavior (TPB) has been widely used to predict individual behaviors in the context of food waste, but the results have been inconclusive. A significant challenge has been the interpretation of the basic constructs of TPB, which has led to mixed results and a lack of consistency in the research. Some studies have identified a significant relationship between perceived behavioral control (PBC) and intention. However, other studies have reported no such relationship. A similar pattern of inconsistency has been observed in the relationship between attitude toward behavior (ATB) and intention, as well as between subjective norms (SN) and intention. This study aims to quantitatively synthesize the varied and inconsistent findings on food waste behavior from 56 included articles selected using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol. The meta-analysis revealed that only two constructs significantly influenced intention, with PBC emerging as the strongest predictor, followed by ATB, while SN showed anon-significant effect. Moreover, intention alone was unable to predict actual behavior regarding food waste reduction. These findings suggest that not all basic constructs of TPB serve as reliable predictors of intention or behavior, thereby underscoring the theoretical limitations of TPB in fully explaining food waste reduction. Subsequent sub-group analysis, incorporating factors such as national income level, terminology differences, continent, and respondent demographics, revealed variations in results regarding the relationship between the basic constructs of TPB. These findings validate the heterogeneity effect, confirming that policy interventions cannot be implemented uniformly.