Eating Disorders: Anorexia and Bulimia
DescriptionAn in-depth report on the treatment and prevention of eating disorders.
Alternative NamesAnorexia; Bulimia
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.
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:
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.
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:
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:
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.
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:
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 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:
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:
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.