Many people with bulimic behavior are probably never diagnosed. The strict diagnostic criteria specify that, in order to be classified as having bulimia nervosa, a person must binge and purge at least twice a week for 3 months. People with bulimia nervosa lead secret lives, hiding their abnormal eating habits. Moreover, it is impossible to recognize people with bulimia nervosa simply from their appearance. Because most diagnoses of bulimia nervosa are based on self-reports, current estimates of the number of cases are probably low. The disorder, especially in its milder forms, may be much more widespread than commonly thought.
Among sufferers of bulimia nervosa, bingeing often alternates with attempts to rigidly restrict food intake. Elaborate food rules are common, such as avoiding all sweets. Thus, eating just one cookie or donut may cause bulimic persons to feel they have broken a rule. Then the objectionable food must be eliminated. Usually, this leads to further overeating, partly because it is easier to regurgitate a large amount of food than a small amount. For intake to qualify as a binge, an atypically large amount of food must be consumed in a short time, and the person must exhibit a lack of control over this behavior.
Binge-purge cycles may be practiced daily, weekly, or at longer intervals. A special time is often set aside. Most binge eating occurs at night, when other people are less likely to interrupt, and usually lasts from '/> to 2 hours. A binge can be triggered by a combination of hunger from recent dieting, stress, boredom, loneliness, and depression. It often follows a period of strict dieting and thus can be linked to intense hunger. The binge is not at all like normal eating; once begun, it seems to propel itself. The person not only loses control but generally doesn't even taste or enjoy the food that is eaten during a binge. This separates the practice from simple overeating.
Most commonly, bulimic people consume cakes, cookies, ice cream, and similar high-carbohydrate convenience foods during binges because these foods can be purged relatively easily and comfortably by vomiting. In a single binge, foods supplying up to 3,000 kcal or more may be eaten. Purging follows in hopes that no weight will be gained. However, even when vomiting follows the binge, 33% to 75% of the food energy taken in is still absorbed, which causes some weight gain. When laxatives or enemas are used, about 90% of the energy is absorbed, as these act in the large intestine, beyond the point of most nutrient absorption. The common belief of bulimic persons that purging soon after bingeing will prevent excessive energy absorption and weight gain is clearly a misperception.
Early in the onset of bulimia nervosa, sufferers often induce vomiting by placing their fingers deep into the mouth. They may inadvertently bite down on these fingers. The resulting bite marks around the knuckles are a characteristic sign of this disorder. Once the disease is established, however, a person can often vomit simply by contracting the abdominal muscles. Vomiting may also occur spontaneously.
Another way bulimic people attempt to compensate for a binge is by engaging in excessive exercise to expend a large amount of energy. Some bulimic people try to estimate the amount of energy eaten in a binge and then exercise to counteract this energy intake. This practice, referred to as "debting," represents an effort to control their weight.
People with bulimia nervosa are not proud of their behavior. After a binge, they usually feel guilty and depressed. Over time, they experience low self-esteem and feel hopeless about their situation. Compulsive lying and drug abuse can further intensify these feelings. Bulimic people caught in the act of bingeing by a friend or family member may order the intruder to "get out" and "go away." Sufferers gradually distance themselves from others, spending more and more time preoccupied by and engaging in bingeing and purging.