Chronic health problems have gradually replaced hunger as the main obstacle to China's sustainable high-speed development, causing considerable economic and social losses. Therefore, the government has begun to adopt front of package (FOP) nutrition labels to promote healthy eating among Chinese residents. However, there are two types of FOP nutrition labels: evaluative and objective nutrition labels. And in some cases, consumers are more willing to purchase healthy foods labeled with evaluative nutrition labels, and in other cases, they prefer to purchase healthy foods with objective nutrition labels. It can be seen that the impact of FOP nutrition labels on consumers' healthy foods purchase intention may vary in different situations.

However, previous studies have not reached a consensus on how FOP nutrition labels affect consumers' purchases of healthy foods. Although most studies have found that consumers prefer healthy foods with evaluative nutrition labels to objective nutrition labels, some studies have come to the opposite conclusion, suggesting that objective nutrition labels are more effective in promoting consumers’ purchases of healthy foods. Some studies have also suggested that the impact of FOP nutrition labels on consumers' purchase of healthy food depends on other factors (e.g., processing context and relationship norm). However, the vast majority of these studies are based on the differences in the interpretability or ease of understanding of nutrition information between two types of FOP nutrition labels. Whether consumers are given the space to process nutrition information according to their own health needs is also an important difference between evaluative nutrition labels and objective nutrition labels. Yet, there are few studies exploring this research question from this perspective. Therefore, according to the utility theory, the current research introduces individual social class, explores the joint effect of FOP nutrition labels and social class on consumers' healthy food purchase intention, and reveals the underlying mechanism and theoretical boundary of this joint effect.

This study tested the research hypothesis through three experiments. Experiment 1 verified the joint effect of FOP nutrition labels and social class on the healthy food purchase intention by measuring social classes. That is, consumers from high (low) social classes are more willing to purchase healthy food labeled with objective (evaluative) nutrition labels. Experiment 2 again verified the joint effect of FOP nutrition labels and social class by manipulating individual social class, and examined the mediating role of nutrition information utility in this joint effect. Namely, the match between FOP nutrition labels and social class (high social class - objective nutrition label and low social class - subjective nutrition label) can lead to a higher nutrition information utility, which in turn will increase purchase intention of healthy food. Experiment 3 further examined the negative moderating effect of food health level on this joint effect. That is, as the level of food health increases, the joint effect of FOP nutrition labeling and social class on the healthy food purchase intention gradually weakens, suggesting that food health is also a boundary condition of the joint effect.

This study has several theoretical contributions and practical significance. First, this study introduces individual social class as a joint variable and proposes for the first time the joint effect of FOP nutrition labels and social class on consumers' healthy food purchase intention. This enriches and develops the literature on nutrition labels and health consumption. Second, this study further reveals the mediating and moderating effects of nutritional information utility and food health level on this combined effect, expanding the application scope of the utility theory. In practice, this study provides policy recommendations for the government to promote the development strategy of the Healthy China, as well as promotion strategies for health food producers and operators to sell their products.