Without adequate nutrition the brain cannot function normally. People with eating disorders do not think in normal ways. Some become delusional. They think they are fat when they are skin and bones. They think people do not or could never love them. Their mind constantly tells them how awful they are for starving themselves. They translate everything that is said to them, including compliments or encouragement, into criticism and rejection. Even saying, "I love you" can be translated, "You wouldn't love me if you really knew me."
With starvation, the heart shrinks and becomes weak, resulting in low blood pressure and poor organ function. The deficiency of sodium, magnesium, calcium, and especially potassium salts by the anorexic's poor diet can cause electrical defects in the heart that can led to a weak heart unable to support or supply other body organs with what they need to function. Inadequate nutrition can prevent digestive enzymes from being produced which impairs digestion and causes bloating which is perceived by the anorexic as weight gain, rather than what it is "indigestion." A weak heart and poor nutrition can cause liver damage and kidney failure. Anorexics have a reduced white blood cell count leading to impaired immunity, anemia and weakness. The thyroid gland is nearly always impaired in anorexia resulting in cold intolerance, dry skin, and brittle hair. When weight drops below 70 percent of the ideal the body's hormonal function becomes similar to that prior to puberty. Menstrual periods stop and secondary sexual characteristics are lost, sometimes these never can be regained, even with hormone therapy. The loss of calcium can lead to premature osteoporosis. Anorexia carries the highest risk of death due to the multiple organ traumas that come from starvation which weakens the heart and it's ability to help the other organs function.
If purging is excessive, confusion and disorientation may result. Seizures are more frequent in Bulimia than in anorexia, probably because more salts are lost by vomiting than avoided in starvation. Vomiting results in inflammation of the esophagus, eventually making swallowing difficult and surgical treatment necessary. The misuse of laxatives actually causes constipation. Restoration can take years,if it occurs at all. Laxatives rarely prevent weight gain unless damage to the small bowls occurs which may or may not be able to be treated. There is an erosion of teeth which leads to early tooth loss. Liver function can be impaired by bulimia, this is especially true when bulimia is associated with alcoholism. The parotid (mumps) glands often swell, giving the patient a chipmunk-like appearance. Bulimic patients are more likely to die from cardiac arrest (sudden heart stoppage) caused by the salt and water imbalance that results from purging. Bulimics also have greater risk from impulse control disorders, including drugs and alcohol, which themselves carry a high mortality rate.