830 NUTRITION AND HEAT REGULATION. 



which they form fat. Some upon relatively small diets form much 

 fat, while others remain thin in spite of the ingestion of large amounts 

 of food. Voit has indicated the general reason for this difference 

 namely, that it depends upon the capacity of the body to destroy 

 food material. When food is supplied and absorbed in excess 

 of this capacity the excess is stored mainly as fat, and to a small 

 extent as glycogen or as new protein. A diet which will give such 

 an excess to one individual may in the body of another of the same 

 weight be all consumed. The oxidizing capacity of the body 

 differs in different individuals and some will lay on fat more readily 

 than others, because for them an excess of material is provided by 

 a relatively small diet. Fundamental differences of this character 

 in the properties of the protoplasm are frequently transmitted by 

 heredity through many generations. Those individuals who show 

 little tendency to lay on fat may be made to do so by largely in- 

 creasing the amount of food, or more certainly by altering the mode 

 of life. A sedentary life, absence of worry, etc., may lead to a 

 tendency of this kind, while a very active muscular life has the 

 opposite effect. Men who lead a very muscular life farmers, 

 fishermen, etc. are rarely disposed to accumulate fat to a notice- 

 able degree. So also the use of alcoholic beverages may indirectly 

 favor accumulation of fat, partly because the oxidation of the 

 alcohol protects the fats and carbohydrates from oxidation, and 

 partly also, perhaps, because long-continued use of alcohol may 

 depress the oxidizing capacity of the tissues. The tendency to 

 form fat may exhibit itself in some cases to such an extent as to con- 

 stitute an almost pathological condition. Obesity may be coun- 

 teracted by altering the mode of life, especially by taking much 

 muscular exercise, and by reducing the diet, so that the total amount 

 of calories represented do not exceed one-half to three-fifths that 

 recognized as the usual average (see p. 849). The diet for such 

 purposes should not only be reduced in amount, but should be as 

 free as possible from excess of fats and carbohydrates, consisting of 

 such material as eggs, fish, lean meat, salads, fruits, etc.* 



Summary of the General Functions of Fat. The general 

 functions fulfilled by the fats may be summarized briefly under 

 the following heads: (1) It provides a store of reserve food which 

 is used by the body in case of deficiency of food or complete starva- 

 tion. The fattening of hibernating animals before their winter 

 sleep and the humps of the camel give conspicuous examples of this 

 peculiarity. (2) By its oxidation in the body it furnishes a part 

 of the heat energy necessary to maintain the body temperature. 

 On account of its high combustion equivalent (1 gm. of fat yields 

 9.3 Calories) fat is very effective in this respect. Inhabitants 



* For practical directions concerning the treatment of obesity by dieting 

 see Gautier, " L'alimentation et les regimes." Paris, 1904. 



