Three main features need to be present to make a diagnosis of bulimia nervosa:
- Recurrent binge eating. A “binge” is an episode of eating during which an objectively large amount of food is eaten, taking into account the circumstances, and there is a sense of loss of control at the time.
- One or more extreme methods of weight control; (recurrent self-induced vomiting, laxative or diuretic misuse, excessive exercising, sustained dietary restriction).
- Over-evaluation of shape and weight and their control; that is, judging self-worth largely, or even exclusively in terms of one’s shape and weight, and one’s ability to control them.
People with bulimia nervosa have recurrent episodes of binge eating, that typically occur against the background of extreme attempts to restrict dieting. Some eat virtually nothing outside their binges, and most others diet strictly. Many make themselves vomit after each binge in order to eliminate the food they have eaten. Some misuse laxatives, diuretics, or diet pills or exercise excessively for this purpose.
The binge eating and extreme methods of weight control are required to occur, on average, at least once a week for three months. The person cannot also have a current diagnosis of anorexia nervosa. This means that the person cannot be significantly underweight.
Bulimia nervosa tends to be self-perpetuating and has little tendency to remit spontaneously, although it can wax and wane in severity.
Bulimia nervosa mainly occurs in women, with the majority being in their 20s. The proportion of males is unclear, although it seems to be less than one in 10. The disorder usually starts in the late teenage years with a period of restrictive dieting. Then, after a variable period, this pattern becomes punctuated by recurrent episodes of binge eating. In about a quarter of cases people develop anorexia nervosa first and then progress to bulimia nervosa.