Abstract: Eating behavior is not only regulated by the biological needs of people, but is also affected by emotional states, motivations, diseases, and more. There is a complex relationship between emotion and eating behavior. Consuming food can influence people's emotion. On the other hand, food attention, subjective appetite, and food intake can be influenced by emotion. Many studies have focused on emotional eating due to negative emotions. However, fewer studies focus on the effect that positive emotion has on eating behavior. The relationship between positive emotion and eating behavior is still controversial, as the relationship is underrepresented in research. The present study analyzed the eating behavior of clinical and non-clinical individuals who were affected by negative or positive emotions, and further explored the neurophysiology of eating behaviors and the various theories of the effect that emotions have on eating behaviors. The results showed that negative emotion increased attentional bias and intake for food and subjective appetite in the general population. This process was also affected by other factors; for example, modest women may restrict their food intake while experiencing negative emotions, so they may regain a sense of control which would offset the unpleasant feelings they were experiencing. In this study, there were two results regarding the effect that positive emotion has on eating behaviors. One theory was that positive emotions broaden momentary thought-action repertoires of people, which in turn builds their endurance. This leads us to believe that people resist food intake after positive emotion is induced. However, contrarily, positive emotion could increase hedonistic behavior in people, thus increasing food intake to maintain the experience of pleasure. Negative emotion increased both attention bias for food cues and subsequent intake in people with bulimia nervosa and binge eating disorders. Negative emotion causes decreased food intake in people suffering from anorexia nervosa. Positive emotion decreased binge eating in people with bulimia nervosa and binge eating disorders and relieved restrictive eating behaviors in people with anorexia nervosa. According to the reward theory, negative emotion can enhance reward sensitivity toward food. Following increased food intake, this process may show a synergy effect in the amygdala, insula, orbitofrontal cortex, striatum, and ventromedial prefrontal cortex. Negative emotion ruins the inhibitory control of individuals, meaning that they may begin to overeat, in association with the activation of the anterior cingulate cortex. According to self-related theory, negative emotion induces negative self-awareness. People can show attention bias due to immediate environmental stimulus, as overeating is meant to help people escape from their own negative self-awareness. Placing their attention on binge eating allows people with bulimia or other binge eating disorders to avoid dealing with information or environmental stimulus that may be hurtful. From the perspective of social culture, most eating behaviors with positive emotion have some special or celebratory meaning which increases the hedonic-oriented eating behavior of the individual. In general, the association between emotion and eating behavior has a certain regularity to follow. In the study, during a negative emotion, an individual's eating behavior manifested in an extreme, unhealthy pattern, whether that meant an increased or decreased food intake. This study found a direct association between emotion and eating behavior; However, social culture, symbolism and connotation of certain foods, and an individual's default eating styles (disinhibited and restrained eating) should be considered alongside the influence that emotion has on eating behaviors. In addition, most past studies self-reported food intake and subjective appetite as recorded by the individuals as the measurement. Future studies should adopt neuro-physiological methods to explore the effect of emotion on eating behavior and study a small set of neurons in the hypothalamus which regulates appetite, for example.

Key words: positive emotions, negative emotions, eating disorders, binge eating