146 THE PKOTEIN ELEMENT IN NUTRITION 



value of the diets are taken into consideration. Chittenden 

 would not only lower the protein standard, but would likewise 

 decrease materially the potential energy of diets. Whatever 

 may be the true physiological requirements of the body for 

 protein in maintaining it in a thorough condition of efficiency, 

 there can be no doubt concerning the recognized fact that the 

 total energy requirements must be met by the oxidation of the 

 food partaken of, unless the organized tissues or reserve materials 

 are to be drawn on. Benedict, from a series of brilliant experi- 

 ments, carried out by means of the respiration calorimeter, has 

 shown that a man of average size, weighing 66 kilos, and at rest 

 within the calorimeter, in twenty-four hours expends about 

 2,270 calories. The average individual under ordinary condi- 

 tions, but not at work, would require more ; whilst the same 

 individual engaged in labour will dissipate large amounts of 

 energy in proportion to the work done. Quantities up to 600 

 calories per hour have been recorded as the output of energy by 

 a professional bicycle rider. 



It has been shown from these experiments that the total 

 energy estimated by Chittenden for some of the dietaries his 

 subjects lived on was considerably less than the quantity neces- 

 sary to meet the ordinary requirements of the body, and markedly 

 lower than that essential for the body at work. The case of 

 Mr. Fletcher, already briefly referred to, is most instructive 

 from this standpoint. Professor Chittenden concluded that 

 Mr. Fletcher was able to perform the work of a member of the 

 Yale University crew on an intake of 1,700 calories. Exact 

 observation on Mr. Fletcher for three days in the respiration 

 calorimeter, most of his time being spent reclining very quietly 

 on a cot, or sitting reading and occasionally writing on a type- 

 writer, showed the average output of energy to be 1,896 calories, 

 whereas the amount of energy actually derived from the food 

 averaged only 1,357 calories. 



In view of these results when at rest, Benedict states that it 

 is safe to assume that Fletcher could not have taken the exercises 

 of the Yale University crew on an expenditure of less than 

 3,000 calories. If the estimate of 1,700 calories of intake be 

 correct, then he must have drawn on his tissues to an extent of 

 1,300 calories daily, or about one-third pound of body fat. 

 Yet Chittenden records that not only was he in a condition of 

 nitrogenous equilibrium, but that his body weight also remained 

 practically unchanged. 



