Abstract: Large quantities of suboptimal food, which contain defects but are perfectly safe for consumption, are wasted. Commercializing suboptimal food has become an important strategy in reducing food waste. However, suboptimal food marketing intervention strategies are numerous and complex. There is a lack of logical sorting out and clear classification of these strategies, and the current experimental results on the effectiveness of marketing intervention strategies for suboptimal food have exhibited inconsistency.
This study adopted a meta-analysis approach to review empirical research on marketing intervention strategies for suboptimal food. Based on the Elaboration Likelihood Model (ELM), suboptimal food marketing intervention strategies were classified into two categories: cognitive-oriented and affective-oriented, with cognitive-oriented marketing intervention strategies including “price promotion”, “emphasizing other value attributes” and “ugly labeling”; and affective-oriented marketing intervention strategies including “anthropomorphism”, “sustainability appeals” and “boosting self-esteem”. It assessed the effectiveness of cognitive-oriented and affective-oriented marketing intervention strategies in influencing consumer evaluation and purchase intention toward suboptimal food. Additionally, the study aimed to identify variables that may impact the effectiveness of these strategies. In total, 32 relevant primary studies were included, comprising 94 effect sizes from 57 independent samples. This study used Comprehensive Meta-Analysis 3.0 for data processing and selected Cohen's d as the effect size, with higher values indicating better intervention effects. Result showed that both cognitive-oriented and affective-oriented marketing intervention strategies could effectively improve consumers’ positive evaluation and willingness to purchase suboptimal food with a moderate level of efficacy. Moreover, affective-oriented strategies demonstrated a better intervention effect compared to cognitive-oriented ones. This study further systematically evaluated and compared the effectiveness of six specific strategies on food evaluation and purchase. In terms of food evaluation, the intervention effect of “emphasizing other value attributes” was the strongest. In terms of food purchasing, “anthropomorphism” was significantly more effective than “emphasizing other value attributes,” “sustainability appeals,” and “price promotion,” but not significantly different from “ugly labeling” and “boosting self-esteem.” Additionally, factors such as suboptimal food characteristics, marketing features, and customer characteristics were found to moderate the effectiveness of these interventions. Regarding suboptimal food characteristics, cognitive-oriented marketing intervention strategies had a significantly greater effect on farm produce than on processed food. Regarding marketing characteristics, strategies that use images were more effective than those that use text; marketing intervention strategies were more effective when suboptimal food was displayed alone compared to being displayed alongside superior food; and marketing intervention strategies were more effective in farmers' markets compared to supermarkets. Regarding customer characteristics, affective-oriented marketing intervention strategies were significantly more effective for female consumers than for male consumers; cognitive-oriented marketing intervention strategies were significantly more effective for younger customers than for older customers; and suboptimal food marketing intervention strategies were significantly more effective in collectivist cultures compared to individualist ones.
The theoretical significance of this study was reflected in three aspects: (1) Current research on suboptimal food marketing intervention strategies lacks systematic review and classification, and experimental results on their effectiveness are inconsistent. This study, based on the ELM, classified suboptimal food marketing intervention strategies into cognitive-oriented and affective-oriented categories and assessed their effectiveness. (2) This study systematically evaluated and compared the effectiveness of six specific strategies on food evaluation and purchase. (3) This study also proposed an integrated model to analyze the boundary conditions for the effectiveness of marketing intervention strategies for suboptimal food, which broadened the horizon for future research on suboptimal food. Practically, this study helped food companies' marketing departments and governments to adopt targeted suboptimal food marketing intervention strategies. For example, food companies can set up a separate display area for suboptimal food, allowing consumers to focus more on these food; at the same time, the characteristics of different retail environments should be taken into account when choosing sales channels, and supply suboptimal food to farmers' markets can enhance their sales and promotional effectiveness.
Currently, most empirical articles on suboptimal food marketing intervention strategies focus on food with suboptimal appearance and less on food nearing its expiration date. In fact, there are many food nearing its expiration date on the market, such as bread and yogurt near the shelf life. Future research can increase the attention to this type of food and target feasible marketing intervention strategies. In addition, the psychological mechanisms of suboptimal food marketing intervention strategies have been less explored, and future research could further explore the mediating mechanisms in the relationship between suboptimal food marketing intervention strategies and consumer purchase.

Key words: suboptimal food, marketing intervention strategies, meta-analysis, cognitive orientation, affective orientation