Bulimia Nervosa:

Bulimia Nervosa is a medical condition, but also is an emotional condition in which one has an obsessive desire to lose weight, when they have bouts of extreme over eating. These episodes are usually then followed by depression, self- induced vomiting, purging, fasting, and sometimes an overuse of laxatives. Sometimes, but not always, people who have Bulimia Nervosa also may have Anorexia Nervosa which is also a form of preventing weight gain.

(http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001381/#adam_000341.disease.causes)