The degree of weight loss varies from tumor to tumor. The monthly weight loss of some tumor patients can reach five to ten percent of the total body weight. Tumors produce a series of biological mediators in the process of growth, which directly affect the energy metabolism of the host, and even interfere with the body’s metabolism, such as lactic acid accumulation, tumor necrosis factor, etc., and ultimately affect the body’s nutritional metabolism, leading to protein depletion, fat metabolism, and glucose deficiency, which results in the host’s weight loss. Early weight loss is not obvious in most tumor patients, and with the severity of the disease, weight loss can reach five to ten percent of total body weight per month. In the case of tumor-induced weight loss, the patient needs should be supplemented in a balanced manner with foods high in calories, vitamins, and proteins to avoid further worsening of symptoms. At the same time, actively treat the tumor and choose treatment methods such as chemotherapy, radiotherapy and surgery according to the specific conditions of the patient in order to control the development of the disease as much as possible. Tumor patients are advised to go to the hospital in time and follow the doctor’s instructions for active treatment.