Anorexia nervosa, often referred to simply as anorexia, is an eating disorder, characterized by low weight, food restriction, fear of gaining weight and a strong desire to be thin. Many people with anorexia see themselves as overweight even though they are, in fact, underweight. They often deny that they have a problem with low weight. They weigh themselves frequently, eat small amounts and only eat certain foods. Some exercise excessively, force themselves to vomit, or use laxatives to lose weight. Complications may include osteoporosis, infertility and heart damage, among others. Women will often stop having menstrual periods. In extreme cases, people with anorexia who continually refuse significant dietary intake and weight restoration interventions, and are declared incompetent to make decisions by a psychiatrist, may be fed by force under restraint via nasogastric tube after asking their parents or proxies to make the decision for them.