Relation of body energetic status to dietary self-selection in Sprague-Dawley rats

Self-selection from carbohydrate, protein and fat sources including essential micronutrients was studied in male Sprague-Dawley rats that were 4 weeks of age at the beginning of the experiment. During the experimental period of 14 days, the intake of carbohydrate and fat was quite constant, whereas that of protein increased gradually. The mean intake of carbohydrate, protein, and fat was 31.1 +/- 3.5%, 56.1 +/- 4.6%, and 12.8 +/- 2.8% of the total energy intake, respectively. Animals fed on a mixed diet consisting of high sucrose, consumed 65.1% of their daily energy as carbohydrate, 17.6% as protein, and 17.3% as fat. Total energy intake and body weight gain were not significantly different between the rats on self-selection and those fed on the mixed diet. These results indicate that young rats on dietary self-selection were able to gain body weight comparable to that of rats fed on the mixed diet. Body energetic status affected self-selection patterns. In rats fasted for 5 days or fed on a protein-free diet for 21 days, fat intake increased, but protein intake decreased. On the other hand, fat intake decreased in animals given a sucrose diet higher in energy content than the stock diet; these animals exhibited increased accumulation of body energy. These results indicate that dietary self-selection is closely related to nutritional and physiological body requirements.