178 NUTRITION, DIETETICS AND ANIMAL HEAT 



Formation of Adipose Tissue. The adipose tissue in the 

 body is not the result of direct deposition of the oleaginous 

 foods. The amount of fat taken on in a given time by some 

 animals, as hogs, is often far in excess of the quantity of 

 fat in the ingesta. Adipose tissue is, under normal condi- 

 tions, the result always of changes due to protoplasmic ac- 

 tivity. It is formed by the tissues chiefly from the carbohy- 

 drates, but also to a less extent from the proteids. The 

 chemical changes by which sugar is converted into fat are as 

 yet undetermined, but there are so many evidences of an in- 

 crease in body fat upon an excess of carbohydrate food that 

 the fact itself that this class of food is the main source of 

 fat is no longer disputed. 



As regards the formation of fat from proteids, it is 

 thought that the molecule is split up into a nitrogenous mole- 

 cule, which is discharged as urea, and a non-nitrogenous, 

 which at once, or after undergoing other changes, is depos- 

 ited as fat. Experimental observations demonstrate that the 

 liver produces gyycogen on a purely proteid diet. Since 

 glycogen is a carbohydrate, and carbohydrates are the chief 

 source of body fat, it is not improbable that the non-nitro- 

 genous molecule of the proteid dissociation takes the form 

 of glycogen and is later converted into fat after the manner, 

 whatever it may be, of the glycogen introduced in carbohy- 

 drate form. When the carbon discharged is less than the 

 carbon ingested the deficit is thought to be retained to form 

 fat, which is deposited as a reserve to be used whenever its 

 oxidation may become necessary as a supply of energy. 



It follows that to reduce body fat the carbohydrates should 

 be largely interdicted, while to increase it they should be 

 taken in excess. In human beings proper regulation of the 

 diet is more efficacious in reducing than increasing the 

 amount of adipose tissue. 



Adipose Tissue a Reserve Supply of Energy. The carbo- 

 hydrates and fats are preeminently the energy-producing 

 foods, and of these the carbohydrates, for reasons indicated, 



