VARIATIONS IN DIETS 



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that certain foods cannot be used at all. The diet, there- 

 fore, which is proper for a person in good health may 

 be most injurious for one who is ill. 



To activity. Another important factor in determin- 

 ing the amount of food necessary for the body is the 

 amount of muscular activity. Of two healthy adults 

 of the same weight and age, the one who is active re- 

 quires more food than the one who is not, because the 

 former is constantly having to oxidize food materials 

 for the production of energy. 1 If the inactive man 

 should eat and absorb as much as the active one, in- 

 stead of oxidizing it all, he would store the excess as fat. 



Variations in diet. Between the amount of food re- 

 quired by the body and the amount actually eaten, there 

 is often a wide divergence. If a person's appetite is 

 good or if he can afford to tempt it with luxuries, he 

 may overeat ; if poor, he may fail to have enough to eat. 

 It is probably true that many persons eat too much pro- 

 teid, especially in the form of meat. Proteid can be 

 stored in the body but slowly, even during the grow- 

 ing period of youth. In adult life, only a comparatively 

 small amount is needed to make good the wear and tear 

 of the active tissues. Since the greater part of it can- 

 not be stored, it is immediately oxidized for the produc- 

 tion of energy, and its waste products of urea and uric 

 acid are removed by the kidneys. Up to a certain point, 

 the kidneys are able easily to do this. If the proteid 



