Further Experiments on the Relation of Fat to Economy of Food Utilization

Publisher Website
Google Scholar
Abstract
In two separate experiments a study was made of the relation of dietary fat to the amount of spontaneous voluntary activity in the mature albino rat. Due to the difficulty of measuring activity directly, it was estimated as the difference between the total heat production measured with and without activity. In the first experiment the total heat production of two groups of 12 rats each was measured by the carbon-nitrogen balance method for 4 periods, each of two days' duration, with the animals being permitted normal freedom of movement during the respiration measurement. Equicaloric diets of either low (2%) or high (30%) fat content and containing the same amount of protein, vitamins and minerals were fed, with reversal of diets being made when the experiment was half completed. It was found that the heat production, as well as the utilization of nitrogen, was not influenced appreciably by the level of fat in the diet. As the heat increment had previously been found to be greater on a low fat diet, it was concluded that the energy expended in all forms of activity must be greater in animals on a high fat diet, varying in a reciprocal manner with the heat increment. To substantiate this claim relative to the amount of activity, a second experiment using the same animals was conducted in which the heat production was measured on consecutive days, first with activity unlimited and then with it limited. For the latter estimation the Haldane procedure was used, with the respiratory measurement lasting 7 hours. The results obtained under both conditions of experimentation agree closely, in principle, with former observations showing approximately the same total heat production on a high fat diet when activity was permitted but a lower heat production when activity was limited.