Eating disorders are typical diseases of adolescence and early adulthood. About 1-3% of female juveniles suffer from anorexia nervosa (AN) or bulimia nervosa (BN). Today AN is still the psychiatric disease with the highest mortality rate. The peri-operative mortality rate of patients suffering from AN is in the range up to 15%. The beginning of AN is a lingering process and the majority of patients show increasingly restrictive eating habits ending in cachexia. Patients are obsessed by the predominant idea of being obese in spite of having a significant underweight. Patients suffering from bulimia break the strict regimen by eating enormous amounts of high calorie food. Such eating attacks are followed by weight reducing measures, mostly vomiting. Most of the physical changes caused by AN are due to starvation and loss of weight. The most significant medical complications are alterations of the cardiovascular system accompanied by decreasing contractility of the heart, bradycardia, electrocardiographic changes as well as disequilibrium of electrolytic and water balance. Most of these symptoms can be reversed by putting on weight.