Loss of appetite occurs commonly among cancer patients. Anorexia is an abnormal loss of appetite that often results in severe weight loss. It affects patients with many different diseases, and is the leading cause of malnutrition in patients with cancer. Anorexia is not the same as anorexia nervosa, an eating disorder that is one form of anorexia.

Loss of appetite can develop when cancer causes pain, nausea, vomiting, diarrhea, constipation, sore or dry mouth, difficulty swallowing or other symptoms. Many cancer treatments, such as chemotherapy and radiation therapy, also cause some degree of appetite loss, as do stress, anxiety and depression related to cancer.

Anorexia can lead to a condition called protein-calorie malnutrition (PCM), and severe cases can result in cachexia, a form of malnutrition. This is especially dangerous for cancer patients, who need proper nutrition to give their bodies strength to fight the disease and cope with its treatments.

Loss of appetite is present in 15 to 25 percent of all cancer patients at the time of diagnosis, according to the National Cancer Institute. Patients are often referred to a registered dietitian, to help them cope with their nutritional problems. In many cases, the dietitian will be part of the patient’s cancer care team.  These professionals can help plan meals that are appealing, as well as rich in nutrients and calories, to meet the needs of the cancer patient. They can also provide recommendations for dealing with the side effects of cancer or its treatments that can lead to anorexia.  

Patients with anorexia may need medications to help stimulate their appetite. However, some patients may be at risk for malnutrition even when eating properly. This is because cancer can also affect the body’s ability to properly absorb nutrients. In such cases, patients may need to receive nutrition via a feeding tube or intravenously to ensure adequate nutrition.