Bulimia nervosa involves a recurring, emotionally driven cycle of compulsive consumption of large quantities of high-calorie food over a short period of time, followed by either induced vomiting or other compensating behaviors. Bulimics use various methods to purge, such as laxatives, drugs that induce vomiting, diuretics, excessive exercise, and fasting.
Bulimia nervosa can be difficult to detect, as compared to anorexia nervosa, because bulimics tend to be of average (or slightly above or below average) weight. Furthermore, some individuals engage in significantly disordered eating and exercise patterns without meeting the full diagnostic criteria for bulimia nervosa.
The diagnostic criteria that is utilized the DSM-IV for bulimia nervosa includes repetitive episodes of binge eating (a discrete episode of overeating during which the individual feels out of control) compensated for by excessive or inappropriate measures taken to avoid weight gain. The diagnosis is made only when the behavior is not a symptom of anorexia nervosa and when the behavior reflects an overemphasis on physical appearance or body mass. There are two sub-types of bulimia nervosa:
- Purging type bulimics, who self-induce vomiting (usually by triggering the gag reflex or ingesting emetics) to rapidly remove food from the body before it can be digested, or utilize laxatives, diuretics, or enemas.
- Non-purging type bulimics (approximately 6% to 8% of cases) who exercise or fast excessively after a binge to offset caloric intake.
Purging-type bulimics may also exercise or fast, but as a secondary form of weight control. For the bulimic, fasting is part of a vicious cycle that is divided into three stages: 1) binging, 2) compensation, and 3) dietary restriction, usually in the form of fasting. After gorging on high-calorie foods, the bulimic is driven to compensate for over-eating. This compensation stage is what distinguishes the two sub-types of bulimia.
When the bulimic fasts, it is usually not planned for a specific length of time, but the fast always has an anorexic quality to it in that the goal is to control weight. This explains why so many anorectics are or were previously bulimics.
Research has indicated that bulimics tend to have specific fasting patterns. For example, bulimics have a tendency not to eat for the rest of the day after a binge. Furthermore, fasting for more than 24 hours is uncommon. After the fast is over, binging begins again, and the cycle ultimately repeats itself.