Malnutrition affects your whole body, making you steadily weaker. It can also decrease your immunity and make you more susceptible to infections. It can promote tissue breakdown that can lead to "fistulas"—leakage from the natural gastrointestinal tract—and poor healing of any surgical wounds. Malnutrition can also worsen any problem of malabsorption of food you may have as a side effect of treatment, resulting in cramping, bloating and diarrhea.
    But the worst effect of malnutrition is the excessive weight loss so often seen in cancer patients. Losing a great deal of weight unfortunately sets up a vicious cycle. A decreased appetite and weight loss lead to fatigue and depression. Depression and progressive weakness lead to reduced activity and an even smaller appetite. More weight loss and weakness lead to a lower resistance to disease and a decrease in immunity. Lower resistance may limit the amount of chemotherapy , radiation therapy or surgery that can be delivered, leading to a poorer prognosis .
    Anyone with cancer who is potentially curable may fail to be cured because of poor nutritional management.

Planning for Improved Nutrition  The key to keeping this cycle at bay is to do everything in your power to prevent malnutrition from occurring in the first place. Once weight loss begins, it is hard to reverse. The time to start thinking and planning for proper nutrition is not when you have already lost a lot of weight but when the diagnosis is made or your treatment gets under way.