2.1. Social Norms
Social norms provide a model for understanding human behavior that is of symbolic importance, particularly for the prevention of misconduct and the promotion of health [
20]. “Social norms” is not a new term that refers to standards of behavior that are recognized and accepted by society at large. The marketing of social norms involves the analysis, planning, implementation, and evaluation of programs designed to influence people’s behaviors to promote individual and social well-being for specific audiences [
21]. In the fields of sociology and psychology, many theories have explored and demonstrated the important role of social norms in human behavior [
22]. Terrier and Marfaing [
23] reported that social norms and commitments have been found to have a positive impact on consumers’ pro-environmental behaviors in hotels. Mirosa et al. [
24] examined social marketing strategies and behavior change tools with doggy bags, showing that positive social norms can help remove barriers to their use and increase the economic benefits, and that restaurants can reduce the amount of food waste by offering consumers doggy bags [
25]. Eatforum [
26] suggested that one strategy is to raise awareness (e.g., social norms) of the consequences of food waste, and social norms could be manipulated to reduce food waste in restaurants [
27,
28]. Jagau and Vyrastekova [
29] found that social pressure, particularly guilty feelings and humiliation, could be elicited by signals of inadequate efforts in reducing the amount of food waste.
2.2. How Attitude Influences Behavior Intention
The theory of planned behavior (TPB) is a continuation of the theory of reasoned action (TRA) in the field of psychology [
30,
31]. TBP was designed explicitly to explain social behavior [
32]. This study applies the affect, behavior, and cognition model of attitudes to analyze consumers’ responses to food waste behavior in restaurants. In agreement with TPB, any consumer social behaviors and behavioral intentions might be elucidated by the behaviors of antecedents. Consumer behavior is interpreted by the intention to perform. In this regard, the attitude toward the behavior is “the degree to which a person has a favorable or unfavorable evaluation or appraisal of the behavior in question” [
32]. According to Blackwell et al. [
33], attitudes determine behavioral intentions, representing what people like and dislike, and in general, people are willing to do what they like and reject what they dislike. Schiffman and Kanuk [
34] argue that attitude is a learned psychological disposition that is intended to be a lasting assessment of a subject. Hence, it is reasonable to conclude that behavior is impacted by internal factors, such as one’s attitudes, and external factors, such as norms. It is extensively conceded that affect and cognition are the building blocks from which consumers’ attitudes are assembled and from which diverse consumer responses are determined. Consumer behaviors are at the center of food waste problems in developed countries [
29]. The most predominant factor of food waste in rich countries is consumer behaviors [
35,
36]. Previous research has shown that consumer attitudes and behavioral intentions determine food waste behavior. For instance, attitudes and intentions around not wasting food have a greater influence on food waste behavior [
37]. Visschers et al. [
38] argued that the behavioral intention of prohibiting food waste and attitudes could predict food waste behavior as well. Stefan et al. [
39] also stated that attitudes are important in determining food waste behaviors.
2.3. Food Waste and Plate Waste in Restaurants
Food waste is an economic and environmental problem [
40]. It threatens global food security [
6]. Food waste occurs at all stages of the food supply chain, with approximately 35% occurring on consumer plates [
41]. Consumers are responsible for the largest share of food waste in the sequence from production to consumption in developed countries [
29]. Parfitt et al. [
4] point out the role of consumers as having great potential for reducing food waste in developed countries. Gustavson et al. [
35] and Secondi et al. [
36] also pointed out the most important factor of food waste in developing countries is consumer behavior. Silvennoinen et al. [
13] indicated that the main reason for food waste in restaurants is not the stage of food preparation, but the customers who dine in restaurants and the service processes. As more people are away from home and there is a growing demand for food prepared and served outside the home all around the world, reducing food waste has become an important way to achieve sustainability in restaurants [
6].
The challenge of food waste in restaurants is of particular concern for sustainability, as it has undermined the environmental sustainability of the global food service supply sector [
3]. Increased household incomes and too many choices drive consumers to buy too much food, resulting in edible food being wasted [
42]. A large proportion of restaurant food waste is due to consumers, which highlights an important opportunity to change consumer behavior. One of the main drivers of food waste in restaurants is irresponsible consumer behavior [
43]. Since consumers only throw away a small amount of food, they do not have to worry about it and do not bother to know anything further [
44,
45]. In general, consumers feel that wasting food is an inevitable part of consumption. Producers and marketers induce consumers to make impulse purchases by advocating discounts or promotional marketing events, thereby influencing consumers’ purchase decisions, leading to food waste later on [
16].
The problem of reducing food waste in restaurants has attracted the attention of scholars. Many campaigns have been developed and launched in restaurants in an endeavor to reduce the amount of plate waste all around the world. For example, in 2014, the European Union proposed a “Year of Fighting Food Waste”, Italy proposed the Milan Protocol to halve global food waste, and the United Nations announced its latest Sustainable Development Goal (SDG) with a specific target of reducing global retail- and consumer-level food waste and food losses in the production and supply chain by half in 2030. In France, restaurants are required by law to provide take-away bags to customers [
46]. The design and size of trash cans can also be indicative of consumer food waste behavior [
47], and restaurants can reduce food waste by providing customers with shopping bags [
25]. Mirosa et al. [
48] surveyed consumers regarding their values and behaviors around tray waste at a university restaurant. Jeffery et al. [
49] reported that mandatory fines can decrease the amount of plate waste and change consumers’ eating habits in restaurants. Kuo and Shih [
50] used education and coercion methods to study the phenomenon of food waste in school cafeterias by gender. Overall, strategies to reduce food waste include raising ethical awareness [
26], providing bags to consumers [
25], changing plate sizes, giving regulation notices, providing education, and using coercion methods. Although education campaigns on food waste may not be successful in the short term, they may influence consumer behavior in the long term [
51].
In the end, as sustainability issues increase on the social agenda, food waste is creating a crisis and undermining environmental sustainability. From a business perspective, relating to the environment represents an opportunity to achieve organizational performance by minimizing the cost of improvement [
52]. In order to facilitate the growth of the hospitality industry to achieve the goals of sustainability, it has become crucial to pay attention to designing the appropriate strategies and management footprint of environmental sustainability in hospitality operations [
53]. Food waste is a heavy operational burden for restaurants [
54], and lasting and stable profits can help companies extend their lifespan with more investment in society and the environment to survive. Otherwise, balancing the budget to improve sustainability and bring about solutions for economic, social, and environmental problems is crucial to food waste reduction strategies.
Based on the studies mentioned above, this study provides a holistic view of food waste behaviors. A causal chain between social norms (SN), consumers’ attitudes (CA), behavioral intentions (BI), food waste behaviors (FWB), and consumers’ plate waste (CPW) can be established. This demonstrates the role of social norms and consumers’ attitudes in shaping behavioral intentions and food waste behaviors. In this study, FWB is a kind of consumer perception of reducing food waste in restaurants, while CPW is the real situation where consumers actually waste food in restaurants. Most of the research used experimental designs to examine the relationships between those variables [
37,
51,
55,
56]. Unfortunately, no studies have examined the sequential mediating relationships of food waste behaviors in restaurants.
Figure 1 shows the hypothesized conceptual research framework based on previous research. This study also examined the sequential mediating effects of two paths, SN-BI-FWB-CPW and CA-BI-FWB-CPW. Those tests may help us to see how the variables are connected and what the rudimentary mediators are in the sequential sequence. We hypothesized that BI and FWB not only are significant direct antecedents of FWB and CPW, but also act as separate and collective mediators between SN, CA, and FWB. Based on the relevance domains discussed above and the hypothesized conceptual research framework, statistically significant causative relationships among social norms, consumers’ attitudes, behavioral intentions, food waste behaviors, and consumers’ plate waste are verified. This study proposes six hypotheses, as follows:
Hypothesis 1 (H1). Social norms significantly impact behavioral intentions in restaurants.
Hypothesis 2 (H2). Consumers’ attitudes toward food waste significantly impact behavioral intentions.
Hypothesis 3 (H3). Behavioral intentions significantly impact food waste behaviors in restaurants.
Hypothesis 4 (H4). Food waste behavior significantly impacts consumer plate waste.
Hypothesis 5 (H5). There are significant sequential mediating effects of BI and FWB between SN and CPW.
Hypothesis 6 (H6). There are significant sequential mediating effects of BI and FWB between CA and CPW.