Malnutrition is usually divided into undernutrition and overnutrition. I. Undernutrition: Generally caused by inappropriate or insufficient diet, patients mostly have a history of chronic inadequate food intake, gastrointestinal diseases, tumors and other wasting diseases. In clinical manifestations, energy malnutrition is characterized by emaciation, protein malnutrition is characterized by edema, and mixed type has both characteristics, usually divided into three degrees: 1, Ⅰ degree of weight loss of 15%-25%, abdominal skin fold thickness of 0.8-0.4cm. 2, Ⅱ degree of weight loss of 25%-40%, abdominal skin fold thickness of less than 0.4cm. 3, Ⅲ degree of weight loss greater than 40%, abdominal skin fold disappeared. The abdominal skin fold disappears. Second, overnutrition: also refers to obesity, can use the weight in kg as a unit divided by the height in m as a unit of the square, the resulting value to determine the level of overnutrition. Usually <18.5kg/m^2 belongs to the wasting, in 18.5-23.9kg/m^2, belongs to the normal nutritional state, ≥24kg/m^2 judged as overweight, ≥28kg/m^2 for the nutritional state as obese.