Eating Disorders: Anorexia and Bulimia

Description

Alternative Names

Causes

There is no single cause for eating disorders. Although concerns about weight and body shape underlie all eating disorders, the actual cause of these disorders appear to result from a convergence of many factors, including cultural and family pressures and emotional and personality disorders. Genetics and biologic factors may also play a role.

Negative Family Influences

Negative influences within the family play a major role in triggering and perpetuating eating disorders. Some studies have produced the following observations and theories regarding family influence.

• Insecure Infancy. Some experts theorize that parents who fail to provide a safe and secure foundation in infancy may foster eating disorders. In such cases, children experience so-called insecure attachments. They are more likely to have greater weight concerns and lower self-esteem than are those with secure attachments.
• Parental Behaviors. Poor parenting by both mothers and fathers have been implicated in eating disorders. One study found that 40% of nine- to ten-year-old girls try to lose weight generally with the urging of their mothers. Some studies have found that mothers of anorexics tend to be over-involved in their child's life, while mothers of people with bulimia are critical and detached. On the other hand, a 2002 study reported that the father's behavior also plays a very important role in a child's eating disorder. Some research, for example, strongly implicates overly critical fathers, brothers, or both in the development of anorexia in both girls and boys.
• Family History of Addictions or Emotional Disorders. Studies report that people with either eating disorder are more likely to have parents with alcoholism or substance abuse than are those in the general population. Parents of people with bulimia appear to be more likely to have psychiatric disorders than parents of patients with anorexia.
• History of Abuse. Women with eating disorders, particularly bulimia, appear to have a higher incidence of sexual abuse. Studies have reported sexual abuse rates as high as 35% in women with bulimia.
• Family History of Obesity. People with bulimia are more likely than average to have an obese parent or to have been overweight themselves during childhood.

At least one study has reported that the most positive way for parents to influence their children's eating habits and to prevent weight problems and eating disorders is to have healthy eating habits themselves.

Problems Surrounding Birth

In some studies people with anorexia have reported a higher than average incidence of problems during the mother's pregnancy or after birth. These problems include the following:

• Infection.
• Physical trauma.
• Seizures.
• Low birth weight.
• Older maternal age.

Some experts believe that such patients experienced an injury to the brain while in the womb that predisposed them to eating problems in infancy and to subsequent eating disorders later in life. Studies have suggested that people with anorexia often had stomach and intestinal problems in infancy.

Genetic Factors

Anorexia is eight times more common in people who have relatives with the disorder, and some experts estimate that genetic factors may influence more than half of the variances in eating disorders. For example, a 2000 study reported that twins had a tendency to share specific eating disorders (anorexia nervosa, bulimia nervosa, and obesity). Some evidence has reported an association with genetic factors responsible for serotonin, the brain chemical involved with both well-being and appetite. Some inherited traits that might make someone susceptible to eating disorders include the following:

• A genetic propensity toward thinness caused by a faster metabolism and reinforced by cultural approval could predispose some people to develop anorexia.
• An inherited propensity for obesity could also trigger an eating disorder to compensate.
• Inherited personality traits also play some causal role.

Cultural Pressures

The approach to food in Western countries is extremely problematic. Enough food is produced in the US to supply 3,800 calories every day to each man, woman, and child, far more than any single person needs to sustain life. Obesity is a global epidemic, and few people living in this over-fed and sedentary culture eat a meal guiltlessly. One can nearly make the sweeping generalization that everyone who lives in a developed nation is at risk for either obesity or some eating disorder.

One interesting anthropologic study reported the following observations:

• During historical periods or in cultures where women are financially dependent and marital ties are stronger, the standard is toward being curvaceous, possibly reflecting a cultural or economic need for greater reproduction.
• During periods or in cultures where female independence has been possible, the standard of female attractiveness tends toward thinness.

Whether or not the current Western cultural pressure is for fewer children, the response of the media to both the cultural drive for thinness and overproduction of food play major roles in triggering obesity and eating disorders.

• On the one hand, advertisers heavily market weight-reduction programs and present anorexic young models as the paradigm of sexual desirability. Clothes are designed and displayed for thin bodies in spite of the fact that few women could wear them successfully.
• One study reported that teenage boys and girls who made strong efforts to look like celebrities of the same sex were more likely to be constant dieters.
• On the other hand, the media floods the public with attractive ads for consuming foods. And, the emphasis is on "junk" foods.

In a country where obesity is epidemic, young women who achieve thinness believe they have accomplished a major cultural and personal victory. They have overcome the temptations of junk food and, at the same time, created body images idealized by the media. Weight loss brings a feeling of triumph over helplessness. This sense of accomplishment is often reinforced by the envy of heavier companions who perceive the anorexic friend as being emotionally stronger and more sexually attractive.

Excessive Athleticism and the Female Athlete Triad. The cultural attitude toward physical activity is a fitting companion to the general disordered attitude regarding eating. Americans are encouraged to admire physical activity only as an intense competitive effort that few can attain, leaving most people in their armchairs as spectators (and at risk for obesity).

In the small community of athletes, excessive exercise is associated with many cases of anorexia (and, to a lesser degree, bulimia). In young female athletes, anorexia postpones puberty, allowing them to retain a muscular boyish shape without the normal accumulation of fatty tissues in breasts and hips that may blunt their competitive edge. Many coaches and teachers compound the problem by overstressing calorie counting and loss of body fat. Some over-control the athletes' lives and are even abusive to an athlete that goes over the weight limit. (Male athletes are also vulnerable to their coaches' influence. Anorexia is also a problem among this group.)

In response, people who are vulnerable to such criticism may lose excessive weight, which has been known to be deadly even for famous athletes. The term "female athlete triad" in fact, is now a common and serious disorder facing young female athletes and dancers and describes the combined presence of the following problems:

• Eating disorders.
• Amenorrhea (absence or irregular menstruation). Evidence is mounting that overly restricting calories may be more important than low weight in causing menstrual problems. Studies suggest that amenorrhea occurs even in women with normal weight if they severely diet.
• Osteoporosis. Bone loss, on the other hand, appears to be related to low weight. The more severe the weight loss, the more bone is lost.

In one study, female athletes who consumed a high-fat diet (35% of daily calories) performed longer and with greater intensity than those with a standard athletic low-fat diet (27% of daily calories). And such a diet appeared to be more estrogen-protective.

Hormonal Abnormalities

Hormonal problems are rampant in eating disorders and include chemical abnormalities in the thyroid, the reproductive regions, and areas related to stress, well-being, and appetite. Many of these chemical changes are certainly a result of malnutrition or other aspects of eating disorders, but they also may play a role in perpetuating or even creating susceptibility to the disorders.

The primary setting of many of these abnormalities originate in a small area of the brain called the limbic system. A specific system called hypothalamic-pituitary-adrenal axis (HPA) may be particularly important in eating disorders. It originates in the following regions in the brain:

• Hypothalamus. The hypothalamus is a small structure that plays a role in controlling our behavior, such as eating, sexual behavior and sleeping, and regulates body temperature, emotions, secretion of hormones, and movement.
• The Pituitary Gland. The pituitary gland develops from an extension of the hypothalamus downwards. It is involved in controlling thyroid functions, the adrenal glands, growth, and sexual maturation.
• Amygdala. This small almond-like structure lies deep in the brain and is associated with regulation and control of major emotional activities, including anxiety, depression, aggression, and affection.

Stress Hormones. The HPA systems trigger the production and release of stress hormones called glucocorticoids, including the primary stress hormone cortisol. Chronically elevated levels of stress chemicals have been observed in patients with anorexia and bulimia. Cortisol is very important in marshaling systems throughout the body (including the heart, lungs, circulation, metabolism, immune systems, and skin) to deal quickly with any threat. Among the specific effects is inhibition of neuropeptide Y (NPY), a powerful appetite stimulant that also has anti-anxiety properties. This process may serve as a biologic link between extreme stressful conditions in a young person's life and the later development of anorexia, although some imaging studies indicate that stress-hormone related changes occur after anorexia has developed. More work is needed to determine if changes in stress hormones are a cause or a result of eating disorders.

Release of Neurotransmitters. The HPA system also releases certain neurotransmitters (chemical messengers) that regulate stress, mood, and appetite and are being heavily investigated for a possible role in eating disorders. Abnormalities in the activities of three of them, serotonin, norepinephrine, and dopamine, are of particular interest. Serotonin is involved with both well-being and appetite (among other traits), and norepinephrine is a stress hormone. Abnormalities in both have been observed in patients who binge and in those with anorexia or bulimia. Dopamine is involved in reward-seeking behavior, so deficiencies might create a more intense need for rewards, such as carbohydrates. Studies on dopamine abnormalities have been mixed, however.

Low-Leptin Levels. Leptin is a hormone that appears to trigger the hypothalamus to stimulate appetite, and low levels have been observed in people with anorexia and bulimia.

Low Reproductive Hormones. The hypothalamic-pituitary system is also responsible for the production of important reproductive hormones that are severely depleted in anorexics. Although most experts believe that these reproductive abnormalities are a result of anorexia, others have reported that in 30% to 50% of people with anorexia, menstrual disturbances occurred before severe malnutrition set in and remained a problem long after weight gain, indicating that hypothalamic-pituitary abnormalities precede the eating disorder itself.

Compensating for Mood Swings during Binge-Purging Cycles

Low levels of serotonin have been observed not only in eating disorders but also in depression. One theory for the persistence of the binge-purge cycle in bulimia involves restoring serotonin imbalances and so improving mood. It involves the following:

• Bingeing elevates tryptophan, a compound found in food, particularly carbohydrates, which is essential to the production of serotonin in the brain. People may binge in order to produce serotonin, thereby improving their mood. An initial increase in tryptophan, however, produces depression in some people. Both events are consistent with a study on young people with bulimia who reported negative moods before bingeing and even worse moods right after bingeing.
• Such depression may become associated with guilt over bingeing and the need to purge. Right before and after a purge cycle, however, studies report an improvement in mood, which might indicate the delayed increase in serotonin triggered by the tryptophan. The heightened mood after the purge cycle may be due to stimulation of natural opioids that occur during this process.
• The binge-purge cycle might then be stimulated by chemical changes and perpetuated by feelings of guilt and depression after bingeing and release from guilt and euphoria during and after purging.

Infections

In some cases, infection has been associated with anorexia. In such cases, immune factors released to fight these infections may cause inflammation and injury in the areas of the brain that affect appetite and behavior.

Streptococcal Infection. The bacteria responsible for strep throat and rheumatic fever--called group A beta-hemolytic streptococcal (GABHS)--is now a suspect in some cases of anorexia. Some children who have been infected with this bacteria develop a syndrome that includes obsessive-compulsive disorder (OCD), tics, and anorexia nervosa. The syndrome is called PANDAS (Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcus). More research is needed to confirm this as an actual cause of anorexia and to determine if it may be treatable with antibiotics.

Epstein Barr Virus. Epstein Barr, the virus that causes mononucleosis, has also been associated with the development of anorexia.