Anorexia and weight loss are major problems for cancer patients and are associated with increased cancer morbidity and mortality. The current clinical approach is to encourage high calorie food intake. In the present study, we used an animal model of tumor-induced anorexia to evaluate the effect of feeding a high caloric diet on food and caloric intake and body weight of tumor-bearing rats. Tumor-bearing rats fed a diet containing 4.7 kcal/g reduced the amount of food they ate to equal the caloric intake of rats fed a diet containing 3.7 kcal/g. Body weight and tumor growth were not affected by the diet intervention. These data suggest that energy intake is regulated in tumor-bearing rats as it is in healthy animals, albeit at a lower level. These data have implications for further study of the effects of nutritional supplements on food intake and nutritional status of cancer patients.