The Effect of Caloric Density of Food on Energy Intake and Body Weight of Tumor-Bearing Rats
Format of Original
Research in Nursing and Health
Original Item ID
doi: 10.1002/nur.4770180409; Shelves: RT1 .R48x Raynor Memorial Periodicals
OBJECTIVE: The purpose of the present study was to examine the food and energy intake of tumor-bearing rats who are switched to a diet of higher caloric density after the onset of anorexia. The findings from this study should increase our understanding of tumor-induced anorexia and the regulation of food intake in tumor-bearing hosts.
POPULATION: Thirty-two male Buffalo rats weighing between 100 to 120g were housed individually and maintained on a 12-hr light-dark cycle commencing at 6:00 a.m. Food and water were freely available.
INTERVENTIONS: The Morris 7777 hepatoma was aseptically excised from a donor animal and 16 rats were randomly selected for tumor implant, leaving 16 healthy animals as controls. The experimental period lasted for 28 days. For the first 15 days, all animals were maintained on a standard rodent diet. After day 15 of tumor growth, one half of the tumor-bearing and one half of the healthy controls were switched to a diet containing 24% fat. The effects of tumor growth and diet formulation on food intake and body weight were analyzed using three-factor (tumor, diet, days) repeated measures analysis of variance for days 0, 18, 21, 24, and 27 of tumor growth.
MAIN OUTCOME MEASURE(S): By day 23, rats fed the 24% fat diet had reduced the grams of food eaten such that the calories consumed were no longer significantly different from that of rats fed the 5% fat diet. There was no effect of diet formulation on body weight of either healthy or tumor-bearing rats. By day 15, body weight of the tumor-bearing rats was 3% less than controls, by day 24, 7.3% below controls, by day 27, 20% lower. Finally, no significant effect of diet formulation on tumor size was found. On day 27 the mean weight of tumors from rats fed the high caloric diet was not significantly different from rats fed the standard diet.
RESULTS/CONCLUSIONS: The energy intake of healthy animals is regulated relative to metabolic size, and food intake will vary as a function of energy content of food. The data from the present study would suggest that the same is true of anorectic tumor-bearing rats. However, the regulation of food appetite and energy intake in humans is much more complex and use of an animal model does not allow testing of other variables that may affect food intake and energy balance in cancer patients. There is a need for long-term studies to determine if supplemental energy intake can be sustained by cancer patients and whether supplemental protein/calorie intake will arrest their nutritional decline.