The Effect of High Versus Low Protein Equicaloric Diets on the Heat Production of Human Subjects

Abstract

Using the respiration calorimeter, the 24-hour metabolism of two pairs of male college students was measured at intervals during a period of 63 days throughout which time the daily intake of energy and protein remained constant. The two diets were equicaloric but differed markedly in protein. At the end of 63 days the assignment of the diets to the two pairs of subjects was reversed and the experiment continued for 38 days with further measurements of the 24-hour metabolism by direct and by indirect calorimetry. With one pair of subjects, the average daily heat production from the diet high in protein (128.6 gm per subject per day) was was about 5.0% greater than that obtained from the equicaloric diet of low protein content (38.0 gm per subject per day). With the second pair of subjects, no difference in daily heat productions was found. This finding emphasizes the insignificant dynamic effects of high protein diets in contrast to that of meals composed entirely of protein. Under the conditions of the experiment, it appears that a given diet is as correctly represented by the heat production measured at the end of a few days as when measured after several weeks. The percentage of the total heat which was eliminated by the evaporation of water was approximately 31% and was inappreciably affected by the composition of the diets.