Pain caused by the tumor can result in severe anorexia and a decrease in the amount of foods and liquids consumed. Changes in the body's metabolism can also cause nutritional problems. Tumor cells often convert nutrients to energy in different, less efficient ways than do other cells. Tumors may produce chemicals or other products that can cause anorexia and cachexia. For example, tumors can produce a substance that changes a person's sense of taste, so that the patient does not want to eat.
Tumors can affect the receptors in the brain that tell the stomach if it is full.
Tumors can also produce hormone substances, which can change the amount of nutrients eaten, the way they are absorbed, and the way they are used by the body. Effect of cancer therapies Nutrition problems can be caused by cancer therapies and their side effects. The treatment may have a direct effect, such as poor protein and fat absorption after certain types of surgeries, or an indirect effect, such as an increased need for energy due to infection and fever. Surgery Head and neck surgery may cause chewing and swallowing problems or may cause mental stress due to the amount of tissue removed during surgery. Surgery to the esophagus may cause stomach paralysis and poor absorption of fat.