1. INTRODUCTION AND PURPOSE

Appetite is the urge to eat. Appetite is affected by many factors and varies from person to person. The basis of human appetite is the sum of sociological physiological psychological and physical factors. People's eating behaviors depend on factors such as the region they live in and their beliefs. Appetite pushes us to a certain eating behavior. Eating behaviors are the results of behaviors that are affected by determinants such as energy intake and expenditure. Negative emotions such as stress depression and sadness are seen as triggers for eating behavior (1). EE is a tendency to overeat to overcome and suppress negative emotions such as depression anxiety and stress. EE is a condition that causes obesity many diseases and disordered eating behaviors. It is seen that many people define themselves with positive emotions such as happy and peaceful while eating. In addition it has been understood that excessive food consumption is used to soothe emotional deprivation (2).

There are many diseases triggered by EE. These include obesity and eating disorders. When the individual exhibits eating behavior with the guidance of his emotions he either tends to eat excessively and high in calories or he tends to have an eating disorder such as eating and vomiting. Emotionally fed people generally have negative body perceptions. It is inevitable that EE will turn into an eating disorder at advanced levels. After a while people with this problem start to turn to food in every mood change in their lives. One of the factors that trigger is bariatric surgery. It has been observed that the EE behavior of the individual after the surgery causes the regain of the lost weight. The point of this thesis is to understand the effect of EE which is triggered by negative emotions and causes various disorders on the appetite mechanism and health.

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2. GENERAL INFORMATION 2.1. Appetite Mechanism

The human appetite mechanism is affected by biological environmental or psychological factors. Understanding what triggers appetite helps prevent unhealthy diets and obesity. The overall control of appetite is thought to be through the gastrointestinal and fat-derived peptide which represents hunger and satiety. According to research the basis of human appetite is the sum of sociological physiological psychological and physical factors (3). People's food choices depend on factors such as climate geography culture and religion. Contrary to biological factors in energy intake the individual's being affected by the environment is a larger factor. However while losing weight and energy deficit occurs the body responds physiologically. Decreased resting metabolic rate increases muscle efficiency energy intake and appetite. In addition according to a study understanding appetite metabolism can provide preliminary information about the etiology of obesity and weight gain. (3).

Homeostatic appetite regulation begins with the inhibitory effect of leptin. Signals that respond to hunger and satiety responses in the gastrointestinal tract are called episodic signals. The central nervous system triggers nutrition based on homeostatic responses; it triggers energy intake by linking hormones such as leptin ghrelin and insulin. Subjective appetite differs from person to person due to variables. These variables are lifestyle eating behavior diversity surgical interventions and pharmacological effects related to weight loss sensitivity. The most important reason triggering appetite is the positive relationship between energy need and energy intake. While appetite is inhibited cholecystokinin and glucagon-like peptide-1 initiate the satiety chain by receiving peptide tyrosine saturation signals. In meeting the energy during the day leptin and similar hormones trigger the appetite and cause the release of glucagon-like hormones. Leptin is a regulatory signal in energy intake. In addition the inhibitory effect of leptin is more pronounced in lean people than in people with obesity.

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As a result energy needs change homeostatic appetite gets under control also energy intake and energy need are the two most important factors in appetite during weight loss. When one encounters stimuli that affect eating it is likely to evoke appetitive responses. Saturation signals act in a negative direction and provide an inhibitory activation after digestion. Thus appetitive behaviors are suppressed (3 4).

The appearance taste smell and aroma of food are thought to stimulate the appetite mechanism. For instance: it is speculated that animals may connect tastes with appetitive post-digestive stimuli. Findings of a study on this topic make it clear that discriminatory management with cues during food needs is based on learning about their intrinsic perceptual stimulus properties. Just as turning off light has stimulant results that an animal can learn from it can also be thought of as turning on a satiety signal due to food neediness. In nutrient-rich societies undereating happens in reaction to biological hunger or bodily need for food but eating appetizing behavior and eating may be considered instead. It is assumed to be the result of encounters with environmental stimuli that turn strong in condition stimuli. It is confirmed that overeating is the result of a weak point in the ability of satiation to inhibit intake not the consequence of an excessive biological need for food. Finally learning and memory processes underlie is described as the motivational effects of satiation on appetitive behavior (5).

Functioning for the regulation of appetite and energy expenditure leptin requires association of hypothalamic neurons but not the expression of the receptor on neurons. Leptin reduces serotonin synthesis and increases energy expenditure. In order for leptin to regulate appetite mechanism and energy expenditure it must inhibit serotonin synthesis. As a result leptin signals in the brain change and its homeostatic function increases compared to the past. They are also defined as the molecular base for the management of energy metabolism. For example it is possible that signaling through some serotonin receptors is opposed to signaling through others. It is also feasible that different serotonin receptors regulate food intake differently even in the same neuron. Leptin is known to bind to receptors of hypothalamic neurons to regulate appetite and energy expenditure.

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Serotonin is thought to be the primary target in the leptin regulation brain and appetite and energy expenditure are also thought to be related to leptin regulation. The neurons appear to be essential mainly for regulating insulin secretion and glucose metabolism (6).

Şekil 1: Mechanism of appetite (Leptin-and-ghrelin-in-appetite-regulation-Leptin-is- released-by-adipocytes-and-signals. (n.d.).)

The ventral tegmental area (VTA) plays a major role in hedonic nutrition. The part that causes hedonic feeding is the VTA. In a hedonic diet a person who is full consumes food for taste rather than for nutritional needs. This behavior can be triggered by environmental factors such as advertisements or by negative emotions such as stress. VTA is an integrator of hypothalamic hindbrain and midbrain limbic and cortical information.

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Excessive consumption of high-calorie foods is an important cause of obesity. High-calorie foods are often delicious. However when a person is full stress and food can be powerful nutritional triggers. The main reason for the mesolimbic dopamine reward system to turn to high-calorie foods and its relationship with stress-induced nutrition are investigated. Nutrition maintains energy balance but becomes a pleasure when it comes to high-calorie foods. Emotions and environmental factors are the factors that trigger the start of nutrition especially in people with obesity. For this reason it is necessary to work on the neural networks that encode the urge to overeat for the treatment of obesity. VTA serves as a motivator for palatable food stress and cue-induced feeding. That is it adds to the difficulty of adequately limiting an individual's food intake. In addition regions such as the dopamine system and amygdala play an important role in stress-related feeding behavior. However although it is known from research that the ventral tegmental region influences food intake more information is needed on how the physiological release of feeding signals is integrated (7).

Şekil 2: Ventral Tegmental Area (Ödül-yolu. (n.d.).)

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2.2. Eating Behaviors

Eating behaviors are the results of behaviors that are influenced by energy intake and expenditure internal and external determinants (for example choosing food eating watching TV and playing sports). These include characteristics of the food supply an individual's knowledge attitudes emotional state and experiences and the social and cultural context in which the behavior occurs. Disorders in eating behavior can cause EE or eating disorders. Stress or depression is seen as a trigger for eating behaviors. According to a study it is estimated that negative emotions have a much greater effect on eating behavior than positive emotions. (5). Perceived stress according to the individual's stress is directly proportional to EE. It is inversely proportional to the eating pattern. In addition it has been understood that EE is directly proportional to sweet and alcohol consumption (8).

Physiologically the stress response is gastric activity and the release of sugar into circulation. In this case it leads to loss of appetite. Likewise it was observed that as the weight increased the stress level increased and accordingly an increase in EE behavior was observed. Regulation of eating behavior distracts the individual from EE behavior. In other words stress has a positive relationship with EE and a negative relationship with eating regulation. Therefore the development of self-regulation behaviors of individuals may be a solution to prevent EE. In the long run this method of regulating eating behavior is shown to reduce or prevent obesity. Social media covers a large part of the factors affecting eating behavior. It is understood that pro-nutritional pictures on social media attract more attention and lead to eating behavior. This appetitive processing is predicted to stimulate appetite by capturing emotion and memory. Unhealthy foods shared and advertised on social media cause malnutrition and obesity; Likewise it is seen that healthy food such as fruits and vegetables contribute to the prevention of obesity and a healthy diet. This approach supports that image of unhealthy food increase appetite and attracts more attention than healthy foods. In addition it is predicted that eating behavior will be transmitted to social media users who share their meals with emotional contagion. Emotional contagion is the trigger of social media (8).

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2.3. Emotional Eating

EE is the urge to overeat in response to emotions such as anxiety stress or fear. EE is less common in men than in women. This type of EE goes so far as to cause eating disorders weight gain and decline in health (8). EE represents the failure to distinguish physiological feelings of hunger from the desire to use eating as a strategy to manage negative emotions. EE is a condition that triggers overeating and causes obesity and disordered eating behaviors. Additionally the underlying biological causes of EE are still under investigation. One study investigated the hormonal emotional and neural changes caused by stress in people experiencing EE. Blood was drawn from the participants for cortisol and their stress levels were examined. As a result of the research it is seen that anxiety and cortisol rates were higher in people who experienced EE. In line with this result it was understood that those who showed EE behavior showed impaired neuroendocrine and neural responses to psychosocial stress. In other words it is known that stress is a risk factor for the emergence of EE behavior. It has also been supported by evidence over time that the root cause of EE is psychopathological (5).

EE is linked with obesity. Additionally eating disorders such as anorexia nervosa and bulimia nervosa appears to be associated with increased anxiety. The most basic mechanism governing eat ing behavior is hypot halamic -pit uit ary-ad renal (H P A ) reactivity. In the study it was found that increased HPA reactivity to stress was associated with binge eating disorder bulimia and anorexia. In addition it has been understood that EE which causes overeating is positively related to the activation of the amygdala and insula parts of the brain (5). Another mechanism underlying EE may be the HPA axis response to inverted stress as a possible consequence of chronic stress early in life. Rather than responding to stress with neurovegetative symptoms such as hyperactivation and loss of appetite the HPA axis may respond to stress with hypoactivation of the HPA axis and neurovegetative symptoms such as increased appetite and weight gain. Stress or negative emotions can lose their self-control as dieters self-restrict their food intake.

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When malnourished the body cannot distinguish food restriction from real food shortage and acts as if it were in starvation mode: metabolic rate drops hunger and appetite increase. EE is more common in women people who have experienced trauma people with psychological illnesses and people who are prone to negative emotions. EE is quite common in overweight or in adults with obesity especially female adults. In children by contrast the prevalence of EE is much lower than in adults. This suggests that most childhood individuals exhibit a natural anorexia response in response to negative emotions or stress and that EE occurs in the period between childhood and adulthood. Anorexia response may occur due to increased estrogen activation due to puberty (9).

In today's life it is seen that many people describe themselves as being happy when they eat. Based on these observations it was determined that people who thought that eating had positive effects had an abnormality in the reward system evoked by eating. In a study it was determined that the expectation that eating increases positive effect played an important role in the persistent persistence of binge eating behavior in 96 women diagnosed with bulimia nervosa during the 1-year follow-up period (10). On the other hand in the presence of negative emotions such as depression and anxiety in young people who are overweight and seeking treatment it is determined that losing control over their eating behavior and eating as an emotion regulator occur and the rates of depression are higher in these individuals. In a study conducted with a group of women in obesity (n=40) with binge eating behavior it was found that these people ate more food (chocolate etc.) when they were in a negative mood (watching a sad movie). On the other hand it was determined in the first studies on this subject that emotions such as anger and tension calm down 1-2 hours after the consumption of foods rich in carbohydrates and that high blood sugar levels are associated with reduced tension. In one study 10 female and 10 male healthy volunteers in an experiment for 1 month showed that negative emotional changes such as aggression occur when switching from a high-fat diet (41%) to a low-fat diet (25%). In addition it is stated that impulsivity is important in the etiopathogenesis of obesity and that the disorder in the reward system results in eating impulsively (10).

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2.3.1. Emotional Eating and Obesity

Obesity is a global health problem with a combination of behavioral genetic and environmental factors. The relationship between emotion perception and dysfunctional eating behaviors in obesity surgery candidates is being investigated. Studies have been done on this subject and it has been understood that there are emotional and social difficulties that cause obesity and dysfunctional eating behaviors. Eating behaviors such as binge eating EE loss of control in overeating or food addiction are common in obesity. The frequent occurrence of EE in obesity shows the relationship between these two concepts. In order to understand the social cognitive basis of the eating behaviors of people with obesity not only preoperative but also post-operative behavior should be followed. Although not all patients with obesity who have problems in eating behavior have dysfunctional eating behaviors it has been understood that regulating emotions is very important in the emergence of such situations. Negative emotions such as anger and loneliness trigger dysfunctional eating behaviors especially in people with a lack of emotion regulation. As a result individuals with this problem tend to minimize the tendency to express their negative emotions with delicious food. In addition all people with obesity including bariatric surgery candidates show significant impairments in describing their emotions and mental states regardless of gender and age. (11 12).

Memory work is often associated with aging education neuroscience and eyewitness testimonies. They are influenced by similar neuroendocrine signals such as ghrelin and leptin and are associated with hippocampal functions. While learning processes affect eating behavior it has recently been seen how understanding of eating behavior changes future consumption. Obesity in humans is associated with impaired memory and diet-induced obesity in rodents causes rapid refuse in memory. Lesions of the hippocampus adversely affect memory and also cause obesity. Thus it highlights the cyclical relationship between obesity and memory impairment (13).

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2.3.2. Emotional Eating and Bariatric Surgery

The prevalence of obesity in the world has been increasing over the years. The development of obesity is associated with factors such as biochemical genetic neurological environmental physiological psychological and sociocultural problems. Eating behaviors body image perceptions and quality of life of the patients before and after bariatric surgery were examined. It is known that obesity causes psychological problems by affecting the self-esteem and psychology of individuals as well as physical health problems. Obesity is common in people with poor body image perception and poor quality of life.

Bariatric surgery is one of the most effective methodsin the control of weight loss and obesity-related diseases in patients with obesity. Today it has been reported that the prevalence of sleeve gastrectomy surgery has increased compared to previous years. In the observation made significant improvements were observed in the clinical course of diabetes hyperlipidemia cholesterol and hypertension problems in people with obesity who lost weight after bariatric surgery. In the examinations performed after the surgery (at least one year) it was observed that there was a significant improvement in the quality of life and especially in the physical and psychological well-being of the patients with weight loss. Regardless of the type the evaluation of the success of bariatric surgery primarily focuses on weight loss that is the reduction in fat tissue in the body. For this reason patients' eating behaviors are as important as surgery in weight loss after bariatric surgery. It has been reported that individuals feel fat for a long time afterbariatric surgery and female patients are less satisfied with the surgery than men. Difficulties with emotion regulation are one mechanism by which attachment insecurity can affect EE. As many people with obesity have experienced EE difficulty in emotion regulation and attachment insecurity in bariatric surgery candidates may be an important mechanism underlying the association of EE. EE sometimes recurs after bariatric surgery (14 15).

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It has been observed that EE can develop before or after bariatric surgery. EE has been identified by many bariatric surgery programs as a risk factor for poor outcomes after bariatric surgery. Some studies have shown that EE is linked to impaired eating behavior associated with uncontrolled binge eating and low mood due to inadequate weight loss after bariatric surgery. EE is seen as a remedy to alleviate various negative moods or emotions as it has been linked to losing control of a diet. Increasing evidence of the benefits of bariatric surgery over the past decade has resulted in an increasing number of individuals undergoing surgery. Researchers agree on positive developments regarding the direct impact of bariatric surgery on weight loss and obesity-related physical comorbidities in severely patients with obesity. Most current research examining psychological outcomes after surgery relates to a time frame ranging from 6 months to 4 years. It is thought that the increased risk of psychological problems among bariatric surgery patients may focus on body image dissatisfaction negative perceptions and feelings about one's own body. It is thought that these negative emotions may cause EE after bariatric surgery (16 17).

2.3.3. Emotional Eating and Eating Disorders

Eating disorders are psychological disorders that impair a person's physical or psychological health. One of the most important factors that cause eating disorders is irregular nutrition. Research continues to understand the relationship between eating disorders and irregular eating habits. In this direction it has been observed that the daily eating habits of individuals are affected when they are exposed to negative emotions. As a result of research it is predicted that individuals with eating disorders have a very emotional character. According to previous research people with eating disorders display disordered eating behavior when they cannot control their emotions. They use the eating behavior to reduce this stress and get rid of negative emotions. Emotional intelligence is a characteristic that defines the emotional abilities of individuals. A recent study found that eating disorders are triggered by impairments in assessing and managing their own emotional emotions (18).

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Emotional intelligence is also shown to have a negative effect on binge eating. It is observed that there is a direct proportional relation between disordered eating behavior and emotional intelligence. They also defined the relationship between emotional intelligence and eating disorders as negative. Researchers have taken into account gender age emotional intelligence model and region factors to examine the relationship between these two concepts. In terms of age the severity of eating disorders varies in most age groups. When it comes to gender research has shown that eating disorders affect women more. Looking at the region it was understood that eating disorders differ geographically according to the regions. As a result eating disorders were found to be negatively associated with emotional intelligence. It is found that eating disorders can be treated by improving emotional intelligence (18).

2.3.3.1. Binge Eating Disorder

Binge eating is the consumption of excessive amounts of food in a short time with a loss of control. Binge eating is an eating disorder that is positive with poor health outcomes. However it is known that binge eating is a risk factor for diseases such as weight gain obesity hypertension and type 2 diabetes. Therefore understanding the causes of binge eating is important for prevention and treatment. EE is thought to be associated with binge eating. The factors affecting this relationship are as follows; age body mass index (BMI) ethnicity marital status employment status and monthly income. All these features are thought to have an effect on emotional reactivity. The effect of negative and positive EE on binge eating disorder was investigated. Increased negative EE is associated with binge eating. Emotional reactivity is found to influence the relationship between EE and binge eating. Tracing the interactions of EE and emotional reactivity to predict binge eating shows us the truth. Increasing negative EE is known to increase overeating by increasing negative emotions. (19).

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2.3.4. Emotional Eating and Major Depressive Disorder

The major depressive disorder involves changes in appetite and weight in a group of individuals at high risk of weight gain. Overeating appetite disorders and dysregulation of appetite hormones are some of the ways to gain weight. A study examines the relationship between eating behavior and major depressive disorder. This study was conducted among 60 depressed and 60 control participants and compared plasma ghrelin and leptin levels. The ages of these participants are between 18-54 and 68 of them are women. Before participating it was checked whether the participants met the DSM-5 criteria. Also none of the participants had a diagnosed eating disorder. The depressive group was categorized as increased or decreased appetite. In the disordered eating depressed group women experienced greater appetite and weight loss than men. Leptin levels were elevated only in women. This study showed a positive correlation between disordered eating and leptin levels and a negative correlation between ghrelin levels. The results show that high levels of malnutrition occur in major depressive disorder especially in women. Again in line with the results we see that overeating in major depressive disorder is associated with appetite hormones and psychological and physiological factors are also included in this. The research also concluded that obesity increases the risk of major depressive disorder and major depressive disorder increases the risk of obesity. Studies should be conducted to prevent risk factors for weight gain in patients with major depressive disorder (20).

2.3.5. Effects of Emotional Eating on the Heart

Emotional factors play a very important role in the causes of heart diseases. In addition nutrition occupies a large place among these reasons. Psychophysiological measures shown to behaviorally indicate emotion dysregulation such as trait level Heart Rate Variability (HRV) might confirm a decreased ability to regulate effect is related to EE behavior. To further understand the role of affect regulation in EE it may be appropriate to examine a measure of the HRV trait in addition to the person's reported emotion dysregulation. HRV results from the interplay of the sympathetic and parasympathetic outputs of the central autonomic network at the sinoatrial node of the heart.

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Since sympathetic and vagal influences determine physiological responses to emotional experience HRV indices can be used to understand emotional experience in response to environmental factors (21).

For example HRV measures are associated with limited improvement in mental stressors and bulimia nervosa is indicative of a stronger response to sadness and insecurity in patients with binge eating disorder. Also lower HRV levels are associated with anxiety and difficulties regulating everyday emotions and concomitant changes in cerebral blood flow in areas associated with emotion regulation correspond to higher resting HRV levels. Since EE is considered a consequence of emotion dysregulation HRV indices may be effective in confirming this association. In addition emotional eaters were randomized to a state in which they were said to overeat during exposure to a food although they retrospectively rated their mood more negatively compared to those who were told they ate a normal amount despite controlling their ratings of impact following mood induction. Neither mood-level change nor trait-level HRV was associated with food intake following negative mood induction (21).

In a study they examined the relationship between EE behavior and HRV. 52 adolescents between the ages of 13-18 participated in the study. Linear and nonlinear HRV methods were evaluated and associated with EE behavior which was divided into two clusters. A positive relationship was observed between EE behavior and peak high frequency power and a good fit to the regression line was observed although the predictive capacity of high frequency waves was low. As a result it can be assumed that the inadequate vagal response to a physical stressor in adolescents in obesity with high EE levels can be interpreted as an inadequate coping and compensatory mechanism related to the positive emotional responses to regulating food intake (22).

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3. DISCUSSION

EE is an eating behavior that changes direction with our changing emotions. This eating behavior is mostly triggered by negative emotions. Feelings such as being bored angry sad and stressed; Researches have been conducted on how it affects EE behavior. One of these studies is the Emotional Appetite Questionnaire (EMAQ) in which 401 university students participated. The purpose of this questionnaire was to analyze the presence of emotion-induced changes in eating profiles. These changes are to explore differences in BMI age and gender. Stress or depression was accepted as a trigger in this study. Participants showed different eating behavior in response to negative emotions. Most of the participants said they overeat when bored. However they stated that they reduced their food consumption in negative emotions rather than boredom. As a result of the research profiles in which negative emotions affect eating behavior was mentioned. It is estimated that negative emotions show much more variation in eating behavior than positive emotions. At the end of the study while excessive eating behavior developed in response to negative emotions eating behavior did not develop in response to positive emotions (23).

Another study investigated the relationship between eating behavior in university students aged between 18-25 (n=523) and EE and food intake due to stress. According to several results in this study perceived stress relative to everyday students' stress was directly proportional to EE. It was inversely proportional to the eating pattern. It was also understood that EE was directly proportional to sweet and alcohol consumption. However eating regulation was inversely related to sweet consumption. Regarding stress it has been understood that the stress levels of university students are triggered by nationality gender and a healthy diet. As a result of the research BMI and stress rate were directly proportional. Likewise it was observed that the stress level increased as the weight increased (8).

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In a study the effect of other environmental factors that trigger EE such as social media on EE was investigated. This research explains that social media is an appetizingly motivating platform. This appetitive processing is predicted to stimulate appetite by capturing emotion and memory. It has been understood that pro nutritional pictures on social media attract more attention and lead to eating behavior. Because unhealthy food shared and advertised on social media leads to malnutrition and obesity; Likewise it has been seen those healthy foods such as fruits and vegetables contribute to the prevention of obesity and a healthy diet. However this approach has revealed that images of unhealthy foods stimulate appetite and attract more attention than healthy foods. In addition it is predicted that eating behavior will be transmitted to social media users who share their meals with emotional contagion. Emotional contagion is the trigger of social media. During the research it was observed that girls experienced more social influence than boys. As a result of the research it was seen that social media triggered EE through visual memory (24).

A study conducted on the tendency of depression patients to eat emotionally also supported that EE is triggered by negative emotions. In addition research has shown that EE can affect the body not only as weight gain but also as weight loss. In this study it was conducted between 6