Eating disorders are very common today. An increasing number of patients that undergo anesthesia and surgery have some nutritional disorder. These disorders are very versatile starting from obesity to anorexia. Significant changes in all organ systems are present. These pathophysiological changes are increased with the duration of the disease. There are many changes in the functioning of the cardiovascular system in all these diseases and there are significant. Respiratory and ventilatory functions are changed too. There are also many endocrine disorders. As a final result, there are many serious biochemical and coagulation disorders. These patients are often under some drug treatment. Patients could be under psychiatric therapy (psychiatric drugs) and/or could take drugs for relieving symptoms related to the pathophysiological changes in different organ systems. Preoperative preparation of patients must be detailed. All changes must be improved to optimal condition. In addition, it is necessary to think about the possible influence of used drugs on the anesthesia.