More people are being diagnosed with eating disorders, possibly as a consequence of society's emphasis on and preoccupation with thinness. Eating disorders are conditions that involve genetic, biological, psychosocial, and environmental factors. In North America, anorexia nervosa, bulimia nervosa, and binge eating disorder are the most common eating disorders. More women than men are affected by eating disorders.
Anorexia nervosa is a psychiatric condition in which people restrict their food intake or use behaviours to prevent weight gain, because of a false belief that they are fat or for fear of becoming fat or obese. In reality, people affected by this condition are almost always underweight or of normal weight when the condition starts. It is estimated that more than 90% of all those diagnosed with anorexia nervosa are women, often from middle and upper socioeconomic backgrounds. This disorder usually starts in the years between adolescence and young adulthood, with the average age of onset at 18 years. It is rare for anorexia to start after the age of 40. It is estimated that in their lifetimes, 9 in 1,000 females and 3 in 1,000 males will be diagnosed with anorexia. Bulimia nervosa is an eating disorder characterized by repeated and uncontrolled or compulsive binge eating, usually followed by inappropriate ways of trying to get rid of the food eaten. Most often, this involves purging by self-induced vomiting or abuse of laxatives, enemas, or diuretics. It's also sometimes called the "binge-purge syndrome." Some people with bulimia don't purge, but will binge-eat (consuming as many as 20,000 calories at one time) and then compensate for binge eating sessions with other behaviours such as fasting or over-exercising. A person with bulimia may secretly binge anywhere from once a week to several times a day. In most cases, binge eating is followed by purging. A person with bulimia may use as many as 20 or more laxatives at a time.
Bulimia commonly appears in the latter part of adolescence or early adulthood, but it can develop at an earlier or later age. The estimated lifetime incidence of bulimia nervosa is about 1%, with females being 3 times more commonly affected than males. Binge eating disorder is characterized by the same uncontrollable binge eating that is seen in bulimia nervosa, but without any purging behaviours after binge eating episodes. This condition is distinct from overeating or obesity. The estimated lifetime incidence of binge eating disorder is approximately 2%. It is more common in women than men, and the age at diagnosis tends to be older than anorexia and bulimia.