192. Possible Errors

Two facts should be recognized in discussing Dr. Chittenden's conclusions; first, his athletes confessedly ate less during the periods when the nitrogen balance was accurately determined, and second, the energy values were estimated. It is unsafe to conclude, therefore, that the energy values of the average diet of the athletes when under observation was as low as is given. This view is strengthened by the fact that although Dr. Chittenden estimated at 1700 calories the food-energy consumption of Mr. Fletcher, who maintained an apparent body equilibrium while he was given the "drastic exercises" of the Yale University crew, when this subject was tested in the respiration calorimeter in a state of inactivity, his heat output was 1896 calories, 536 calories more than his food contained.1 Dr. Benedict in commenting on this says with good reason that Mr. Fletcher's use of energy when taking the Yale exercises could not have been less than 3000 calories, part of which was at the expense of his body. The maintenance of a nitrogen equilibrium and of uniform body weight, as in Mr. Fletcher's case, is not evidence that the body has not lost substance, for muscular exercise in excess of the food supply is sustained by the body fat as long as it lasts, and weight may be maintained even during a loss of body fat, for this loss may be replaced by water. Moreover, the estimation of available food energy on the basis of the average composition and digestibility is a precarious method. Exact measurements are necessary for exact conclusions.

1 "Metabolism and Practical Medicine," Von Noorden, Vol. I, pp. 260-261. 2 "Physiological Economy in Nutrition," pp. 327-454.

Table XXVII. Heat Production (Energy Use) During 24 Hours1 Subjects In Fasting Condition

1"Metabolism and Practical Medicine," Von Noorden, Vol. 1, pp. 260-1.