Eating disorders include anorexia, bulimia, and paroxysmal overeating (the latter disorder was discussed in the previous Chapter). Anorexia, in which a person eats less than necessary, is life-threatening not only because of the devastating effects of starvation. Anorexia increases the risk of suicide. Bulimia is the opposite of anorexia in relation to food — a person eats more than necessary, but tries to prevent weight gain by using simple methods such as provoking vomiting. Such attempts to compensate for an overabundance of calories distinguish bulimia from normal psychogenic overeating.
Voluntary fasting is historically associated with asceticism. Despite the fact that fasting is a common practice for ascetics of all sexes, in the Christian West, excessive fasting was more common in women. During the reformation, refusal to eat was viewed with suspicion and in many cases attributed to demonic possession rather than special spiritual gifts.
Painful attacks of insatiable appetite and food carousals in the Middle ages are rarely written about because of the comparative lack of food. If there is nothing to eat, then insatiability is not terrible.
Over time, questions of spiritual discipline lose their importance in choosing a diet. At the end of the XVIII century, the standard of female beauty changes, and instead of roundness, public opinion chooses slimness. The elegance of forms becomes a marker of belonging to the upper classes. Byron and the pre-Raphaelites  canonize a new aesthetic ideal — pallor, thinness, a melancholy aura.
In the late nineteenth century draw attention to the prevalence of fasting in the name of the external perfection. It is understandable why people want to be beautiful, but only a person with mental problems can risk his life to change his appearance. This vision of the oddities of eating behavior was not formed immediately. In the classifiers of mental diseases, anorexia was introduced in the 1950s. In the 1980s, as the concept of bulimia was developed, an idea of the spectrum of eating disorders was built.
Initially, in psychiatry, the treatment of eating disorders was tied to childhood traumatic experiences. But gradually, eating disorders are separated from the diseases of childhood and adolescence and they begin to be treated as a separate group of diseases.
In the second half of the XX century, the exchange of information is globalized, the amount of advertising is multiplying around a person, and mass culture actively exploits erotic imagery. Concern about body weight becomes universal. On the one hand, culture dictates the image of the body norm, and on the other hand, modern people have opened unprecedented easy access to high-calorie food. As never before, it is now easy to get fat, and as never before, a person is bombarded with the image of a model body.
It is proved that the richer the country and the more actively a woman participates in social life, the more common anorexia is in the country. In Patriarchal societies, where a woman sits at home in a burqa, eating disorders are rare. Until the 1970s, anorexia was considered a syndrome of Western culture. Its prevalence in developing countries and among the non-white population of the planet remained extremely low.
Mass culture and marketing, of course, are responsible for the fact that girls get anorexia, but socio-cultural factors, as in the case of other mental disorders, work only in combination with neurobiological processes. All modern people are influenced by the cultural ideal of a slim body, but not all become anorexic. So, cultural influence, no matter how pervasive it may be, is not enough. Pathological eating habits have a basis in the biology of the brain.
Closer to the 2000s, there is not only an increase in the frequency of anorexia nervosa, but also its “rejuvenation” with a shift in the peak incidence to adolescence, although the onset at 8-10 years is no longer uncommon. The manifestation of pathomorphosis  of the disease, apparently, is the increase in the clinical picture of anorexia nervosa of the share of bulimic symptoms. There is a tendency to increase the incidence among men.
Eating disorders are easily confused with endocrine diseases and tumors in the brain, which can lead to impaired appetite. The main methodological problem of research on eating disorders is that the state of the brain significantly changes depending on the nature of nutrition. Chronic malnutrition in anorexia leads to changes in metabolic processes in the brain. The picture observed during neuroimaging can occur due to an unhealthy diet, but it can also be the opposite — abnormalities in the brain cause the development of eating disorders.
The neurobiology of hunger began to be studied only in the 1950s. People have always known about how lack of food affects the psyche: concentration and other cognitive functions, including the ability to make decisions, increase irritability, and symptoms of depression appear. Before a rough understanding of the neurobiological aspect of fasting was formed, anorexia was studied from a psychological point of view. Typical behavioral features of anorexics were identified, such as inflexibility of thinking and special attention to irrelevant details at the expense of holistic perception. This brings anorexia closer to autism spectrum disorders. Another important feature is related to emotions — in people with eating disorders, the sensitivity to punishment is increased, and to reward is reduced. There is also a tendency to extremes in behavior — either excessive inhibition, or extreme disinhibition.
The study of the neurobiological basis of these behavioral features, as well as the main characteristic of eating disorders — impaired appetite — has not yet led to a clear understanding of the nature of the disease. Probably, in eating disorders, something is wrong with the connections of the frontal lobes and the striatum. Anorexia is characterized by a decrease in the activity of the striatum, amygdala and hippocampus simultaneously with an increase in the activity of the prefrontal cortex. There is a certain defect in the neural networks associated with appetite and the idea of your own body. Due to a breakdown in the striatum, the body does not respond correctly to food. With bulimia and overeating, motivation is uncontrollably accelerated, and with anorexia it slows down. The body is represented in the parietal cortex. Apparently, there is also some kind of disorder. Abnormalities in this region of the brain are indicated by the fact that people with anorexia do not realize the severity of the disease, just like neurological patients who have damaged the parietal cortex.
Structural and functional changes were also found in the patients ‘ orbitofrontal cortex — the brain structure responsible for feeling full. Also, in anorexia, there is a violation of the islet — the primary cortical center of taste perception.
In General, the brain in anorexia is reduced in volume. The increase in the ventricles and the volume of cerebrospinal fluid makes it look like the brain of people with symptoms of addiction. After the restoration of nutrition, the volume of gray and white matter, as well as cerebrospinal fluid, usually returns to normal.
The combination of anomalies in two neural networks is fundamentally important in eating disorders. The work of cognitive networks in the frontal cortex is incorrectly configured, and at the same time, stability in the system responsible for understanding and implementing the basic needs of the body is lost. This system should ideally form a suitable affective experience when in contact with a stimulus (an attraction to food). At a higher level in the brain structure, neural networks are involved in the planning process (determining the appropriate amount of food). The ensemble of the two systems in eating disorders acts uncoordinated. The fact that these disorders are not some kind of “scars” from malnutrition, proves the discovery of the same features in relatives who do not suffer from eating disorders. Consequently, eating disorders grow on the Foundation of a genetic predisposition.
In the study of neurotransmission in eating disorders, as often happens in modern psychiatry, serotonin and dopamine came to the fore. With serotonin, something similar to what is observed in sufferers of anxiety disorders. The lack of effectiveness of serotonin antidepressants is explained by the fact that serotonin synthesis is reduced in anorexia, and the effect of modern serotonin antidepressants depends on the amount of serotonin released into the space between nerve cells. In other words, antidepressants simply don’t have enough serotonin to accumulate.
Admittedly, science has not yet been able to explain how abnormalities in the serotonin system cause an attitude to food that drives anorexics to exhaustion. Maybe it’s because serotonin affects the choice of action: depending on the amount of serotonin in the prefrontal cortex, a person postpones a reward for later or acts impulsively. In addition, changes in serotonin levels have a negative effect on mood and the ability to enjoy pleasure, which may explain the prevalence of depression in people with eating disorders.
In the reward system, as you know, the main role is played by dopamine. Since eating disorders are obviously associated with a malfunction in the reward system, it can be argued that one of the neurobiological causes of these disorders is an imbalance of dopamine.
Studies conducted in recent years have found many features of brain functioning in eating disorders. Thus, in a gambling experiment in patients with anorexia, the reward center was less active when winning and stronger when losing. In anorexia, the release of dopamine does not cause pleasure, but anxiety, and the reward center of the brain itself is hypersensitive to food-related stimuli. The brain of people with anorexia nervosa perceives the signals of taste sensations as very disturbing and disgusting.
At the same time, dopamine, which is involved in the neural networks that modulate appetite, depends on other neurotransmitters, GABA and glutamate, which in turn are activated with the participation of hormones and neuropeptides (for example, leptin, insulin, ghrelin and orexin). Like many other mental illnesses, eating disorders are a complex problem that involves the entire body.
The genetic component of eating disorders is evidenced by the fact that they are often hereditary. Moreover, if one family member suffers from bulimia, the other may face anorexia, and Vice versa. Over time, in the same person, one disease can pass into another. According to twin studies, the contribution of genetic factors to the development of anorexia nervosa is 50-60 %. Studies that examined the genome of people with anorexia nervosa (full-genome Association search) suggested that not only psychopathological processes, but also metabolic disorders play an important role in the development of the disease.
Endocrinological pathology, most likely, is not a consequence of mental, and develops independently of it. Anorexia-associated genetic variants increase the risk of underweight, and Vice versa: underweight-associated gene variants increase the risk of anorexia nervosa. Low body weight has traditionally been considered only a consequence of psychopathological processes in anorexia. This approach has not allowed the development of reliable therapeutic strategies to help maintain an acceptable weight and mental well-being of patients. New data suggest that, most likely, in anorexia nervosa, along with psychopathology, there is a complex metabolic dysregulation. For this reason, even after therapeutic intervention and nutrition control, it is difficult for patients to achieve a normal body weight.
In addition, the genes associated with anorexia were compared with the results of genetic studies of other mental disorders and various normal conditions. A genetic link between anorexia nervosa and depression, anxiety disorders and schizophrenia was found, which is consistent with available clinical and epidemiological data on their frequent combination. A positive genetic correlation with physical activity levels was also found. This finding helps explain the painfully elevated levels of motor activity and arousal observed in some anorexic patients.
With the help of modern neuroimaging technologies, you can describe the most complex neural connections in the brain and get closer to understanding the causes of the development of a particular disease. Neuroimaging has revealed many aspects of eating disorders. For example, disorders of the integral perception of one’s own body observed in bulimia nervosa are associated with left-sided changes in connectivity in the temporal-occipital areas of the brain, which play a major role in the somatosensory  and visual-spatial systems of the brain. It is known that normally it is in the temporal cortex that the zones responsible for the perception of the body schema are localized. Thus, an increase in left-sided connectivity and a decrease in right-sided connectivity in bulimia nervosa in these areas is completely consistent with these data.
Changes in the prefrontal and limbic regions that are specific to each hemisphere are also interesting. In different studies, it has been repeatedly shown that strengthening the role of the left prefrontal cortex is associated with more purposeful behavior, while strengthening the right prefrontal cortex, on the contrary, is associated with weakened self-control. Food causes a greater increase in regional blood flow in the left prefrontal zone, compared to the right, which indicates the involvement of the left prefrontal zone in the development of bulimia nervosa.
The complex mechanism of development of eating disorders makes them one of the most difficult to treat mental disorders. Psychopharmacotherapy does not promise a dramatic improvement in the condition, except in cases where anorexia or bulimia is combined with depression, anxiety or sleep disorders. Psychotherapy with constant family support, as well as the recommendations of nutritionists when it comes to extremely low body weight — is the main psychiatric help, according to world standards of treatment. Psychiatry can offer nothing but psychoeducation, empathy, and a higher-calorie diet. But still, the latest genetic and neurobiological data on the nature of eating disorders give hope for the creation of new effective drugs and the development of endocrinological drugs in the treatment of anorexia and bulimia.