THE NORMAL DIET OF MAN 729 



This would correspond to a total calorie value of 3055, or, sub- 

 tracting 10 per cent, for the food which is not utilised in the alimentary 

 canal, to 2749 calories. The fat in this diet is rather low, preference 

 being given to the carbohydrate on account of its greater cheapness. 

 It is not advisable to reduce the fat below this limit, since the 

 human body has a need for a certain proportion of fat, in the absence of 

 which the utilisation of the other food-stuffs does not proceed normally. 

 The presence of fat in the diet is especially important in the case of 

 infants and young children, many of the disorders of nutrition pre- 

 valent among the children of the lower classes being largely determined 

 by the absence of the proper quantity of fat from the diet. In the 

 case of severe work this diet may not be adequate to supply the 

 necessary quantity of energy. Thus, for soldiers, Voit's ration during 

 manoeuvres consists of : 



Protein . . . . .135 grm. 



Fat 80 



Carbohydrate . . . . 500 



with a total calorie value of 3348. His ration for war-time 

 consists of : 



Protein 145 grmj 



Fat 100 



Carbohydrate .... 500 ,, 



corresponding to 3575 calories. Even this may be insufficient to 

 supply the energy needs during a period of intense muscular activity. 

 In one experiment by Atwater, in which the individual performed 

 muscular work for a period of sixteen hours out of the twenty- 

 four in a calorimeter, the total energy given out amounted to 

 over 9000 calories in the course of the twenty-four hours. It is 

 probable, however, that in all cases where such excessive calls on 

 the energies of an individual are made, one or even two rest days 

 would follow the day of exertion, so that the deficiency of the food 

 on the day of exertion would be made good by an increased intake 

 of food on the following days. Thus three days' intake of 5000 

 calories would yield sufficient energy for the output of 9000 calories 

 on one day of exertion and of 3000 calories, the normal amount, 

 on each of the two succeeding rest days. The relative part played 

 by the different constituents of a diet in yielding energy to the 

 body has been determined by many observers and especially in 

 a long series of researches by Atwater. On the next page are given 

 details of the daily food in one such experiment on a man weighing 

 76 kilos. 



