Appetite loss, is common among cancer patients. Anorexia is a decrease in or complete loss of appetite that causes significant weight loss in patients with cancer and other diseases. It can occur as a result of cancer, or as a side effect of its many treatments, including surgery, chemotherapy, biological therapy, radiation therapy and hormone therapy.  Anorexia is an almost universal side effect in patients who have widely metastatic (spreading) cancer. Anorexia should not be confused with anorexia nervosa, a primary eating disorder that is one form of anorexia.

Nutrition is the process by which all living organisms assimilate food and use it for growth, energy and for replacement of tissues. Food is chewed and swallowed before it enters the esophagus, a tube-shaped organ that transports food down through the neck and chest and into the stomach.

Nutrients are absorbed into the body during the digestive process. This begins within the stomach, where gastric juices are secreted and mixed with the food into a thick fluid. This fluid is then emptied into the small intestine and further broken down before the nutrients are absorbed into the body.

Improved nutrition has many benefits, including:

• Maintains healthy levels of body weight and strength
• Prevents body tissues from breaking down
• Repairs damaged tissue
• Fights infection
• Improves patient’s long-term prognosis

Cancer patients with appetite loss are frequently diagnosed with protein-calorie malnutrition (PCM), which results from insufficient intake or absorption of carbohydrates, proteins and fats. Patients with this condition do not consume or absorb enough nutrients to meet their body’s metabolic requirements. Changes in the metabolism contribute to loss of skeletal muscle and adipose tissue (fat).

Poor nutrition deprives patients of the strength their bodies need to fight cancer and to withstand the rigors of cancer treatments. Researchers have found a correlation between weight loss and poor prognosis for cancer patients. Poor nutrition can increase the likelihood and severity of side effects associated with treatments, and can increase the risk of infection.

In its most severe form, anorexia and PCM can lead to cachexia, a type of malnutrition that can result in weakness and a substantial, progressive loss of body weight, fat and muscle. Cachexia is suspected in cancer patients who have an involuntary weight loss of greater than 5 percent of their precancer weight within a six-month period. When anorexia triggers cachexia, it is known as the anorexia-cachexia syndrome. About 50 percent of cancer patients suffer from this syndrome, according to the American Cancer Society.

Patients with solid tumors are at particular risk for cachexia. For example, cachexia is associated with cancers of the lung, breast and pancreas.

Cachexia is less likely in patients with blood cancers such as leukemia or multiple myeloma.

Cachexia differs from starvation. A healthy person's body can adjust to starvation by slowing down its use of nutrients. However, the body of a cancer patient does not make this adjustment. As a result, cachexia is identified as the immediate cause of death in 20 percent to 40 percent of cancer patients, according to the National Cancer Institute.

Loss of appetite belongs to a class of manifestations known as nutrition impact symptoms. These are symptoms that affect appetite or impede oral intake. They include:

• Nausea
  
• Vomiting
  
• Diarrhea
  
• Constipation
  
• Mucositis (inflammation of any mucous membrane, including the mouth)
  
• Dysphagia (swallowing impairment)
  
• Alterations in taste and smell
  
• Pain