It is important to realize that, for the most part, these are adaptations that are geared toward survival. In effect, the body is prioritizing its available nutrients for purposes like wound healing and maintaining the immune system. Sometimes, these metabolic changes can become exaggerated or prolonged to the point that they are harmful rather than beneficial to the patient. Significant weight loss and muscle wasting can occur rapidly and can be difficult or even impossible to reverse. The specific nutritional requirements of the pet with cancer are unknown.
Some nutrients are of higher priority than others.
Water is the most essential nutrient. Next, a pet requires adequate calories and protein, followed by minerals and vitamins. Commercial pet foods are balanced so that when a pet eats adequate calories he will also get adequate amounts of all other required nutrients. The typical problem encountered in pets with cancer is reduced food intake, or refusal of pet foods and acceptance only of table foods that lack essential nutrients. A pet with cancer loses weight in part because of decreased food intake and in part because of the metabolic effects of the disease.