Binge eating is an element of another eating disorder, bulimia nervosa. The formal diagnosis criteria are similar: at least two binges per week for an extended period of time. In bulimia, however, episodes of binge eating are followed by purging, periods of fasting, or performance of strenuous exercise - indeed, "exercise bulimia," in which a person eats normally but then engages in strenuous exercise, is an inverse form of bulimia People with binge eating disorder, by contrast, do not purge, fast or engage in strenuous exercise after binge eating. Additionally, people with bulimia are typically of normal weight or may be slightly overweight (the purging, etc., have little to no effect on the subject's body fat), whereas people with binge eating disorder are typically overweight or obese.
Binge eating disorder is similar to, but it is distinct from, compulsive eating. People with binge eating disorder do not have a compulsion to overeat and do not spend a great deal of time fantasising about food. On the contrary, some people with binge eating disorder have very negative feelings about food. As with other eating disorders, binge eating is an expressive disorder - that is, the disorder is an expression of a deeper, psychological problem.
It is actually hotly contested whether binge eating disorder has its own diagnosis. Some believe that it is a milder form, or subset of bulimia nervosa, but others argue that it is its own distinct disorder. Currently, the DSM-IV categorizes it under Eating Disorder Not Otherwise Specified (ED(NOS)), simply stating that more research is needed.
Src: www.wikipedia.org