22 PHYSIOLOGY AND NATIONAL NEEDS 



not work neither shall he eat is seldom carried out in 

 practice ; but the converse that if he does work he should 

 have more to eat is a sine qua non. The peace-time allow- 

 ance for a man doing a day's hard muscular labour is food 

 equivalent to about 3500 calories, and under conditions of 

 extreme work this may rise to more than 4000 in a day. 

 Many people in the time of peace and plenty took food of 

 this high calorific value even if they were not hard workers, 

 and it was such people who as a consequence put on weight : 

 it is just these people who lost their extra weight when 

 rationed in war time. 



But the man who really is putting forth extra energy 

 must either get it from an increase in his food intake or 

 he has to fall back on his reserves ; the first line of reserve 

 is his adipose tissue, and so he becomes thin. This 

 reserve obviously will not last him for an indefinite time, 

 so after a given period, if he still continues to work hard 

 on insufficient food, the more precious protein reserves in 

 his muscles and other tissues will suffer a harmful strain. 



A definite example may help us to realise the thing in 

 figures. Take the case of a well-to-do and not over energetic 

 person. His basal metabolic requirement is 1700 calories, 

 and his daily food in peace time gave him 3500 ; that will 

 leave him 1800 calories for muscular work, which probably 

 he did not wholly use, so that he put on a store of fat. 

 Now suppose he is rationed down to 2500 calories per 

 diem ; in a few weeks most of his superfluous weight will 

 be lost, and his basal requirement will be lowered also, say 

 to 1500 calories ; he will still have 1000 calories left for 

 muscular activities, and this will be all that he can afford 

 to spend without encroaching on his protein reserves. 



THE PLACE OF MEAT IN A DIETARY. Meat is eaten 

 because it forms a concentrated form of easily digestible 

 protein or albumin, and protein is the great repairer of 

 our tissue waste. As a source of energy, it is about equal 

 to carbohydrate and far inferior to fat ; considering its 



