After a malignant tumor grows in the colon, the tumor can rupture, and the tumor causes nutritional deficiency during the growth process and secondary infection after rupture, all these factors can cause the patient to lose weight, as well as blood loss caused by the tumor rupture, which finally triggers anemia and leads to weight loss. In addition, the tumor will produce various toxic factors, which will affect the appetite of patients, especially when right hemicolectomy cancer occurs, the tumor form is mass type, which will lead to nutritional deficiency and wasting. When left colon cancer causes intestinal obstruction, it is difficult for patients to eat, and weight loss is also one of the complications. The reasons for wasting due to colon cancer are as follows: 1, tumor takes a lot of nutrients from human body in the process of continuous growth, which becomes chronic consumption; 2, cancer tissue necrosis produces toxins, which leads to anorexia and fever, that is, cancer fever, anorexia reduces nutrient intake, while fever increases body consumption, which eventually leads to wasting; 3, chronic bleeding, if cancer tissue necrosis destroys blood vessels, it may cause different degrees of bleeding. Especially for patients with colon cancer, rectal cancer and other gastrointestinal tumors, it is more likely to cause chronic bleeding, resulting in patient consumption and anemia. If the causes of colon cancer wasting have been clearly diagnosed, different treatments according to different causes can solve the above problems.