Removing the tumor can correct the problem. Surgery, radiation therapy, and chemotherapy can also have side effects that cause temporary malnutrition and weight loss. The body needs a great deal of energy to heal and recover from surgery. Radiation therapy often damages healthy tissue in the area of the tumor and, depending on the tumor's location, can result in temporary nutritional difficulties. For example, treatment of the esophagus or nearby structures can lead to difficulties swallowing, while treatments in the abdomen can affect the intestines and result in diarrhea or poor absorption of nutrients.
Chemotherapy can have few or many side effects, depending on the regimen and the individual.
Possible side effects include diarrhea, constipation, anorexia, nausea, and vomiting, all of which can affect a person's weight and nutritional status. At one time, some people believed that cancer cachexia occurred because the growing tumor soaked up nutrients to fuel its own growth, thereby starving the body. Others thought this unlikely because most tumors weigh 5 percent or less of a person's weight. In addition, cachexia occurs even in cancer patients receiving excess calories. In the mid-1980s, scientists investigating cancer cachexia performed a revealing experiment.