442 



METABOLISM, NUTRITION, AND DIET 



and others. Rubner states that 82 to 92 per cent, of the fat excess can be 

 stored. The fat stored is of the same kind given in the food, even though 

 the usual fat of the animal is different. The melting point of dog's 

 fat is about 20 C., but by feeding an excess of mutton fat the melting 

 point has been raised to 40 C. The subcutaneous fat of pigs subjected 

 to this experiment is more or less fluid according to the melting point of 

 the fat fed. 



The body fat can also be derived from carbohydrate food, a fact which 

 the practices of the stock feeder and dairyman constantly verify. The ex- 

 periments will present the matter more vividly than pages of description. 



GAIN IN FAT OF A PIG FED ON RICE. (MEISSL AND STROHMER.) 



It is obvious that the 5 . 3 grams of fat and the 66 grams of protein cannot 

 account for the carbon retained, and one must look to the carbohydrate as 

 the source of the fat. 



Jordan placed a Jersey cow on a feed of hay and grain from which the 

 fat was extracted. The cow in 95 days assimilated 5 . 7 pounds of fat, in- 

 creased 47 pounds in weight, and produced 62.9 pounds of fat in the milk. 

 The nitrogen excreted was the equivalent of 33.3 pounds of protein. The 

 non-nitrogenous moiety of the protein, if its carbon had all gone into fat, 

 could not have produced over 17 pounds. Summarized, this experiment 

 shows conclusively that fat is synthesized from carbohydrate. It requires 

 about 2 . 7 grams of dextrose to form i gram of fat, and this condensation 

 takes place with the formation of carbon dioxide and water and the libera- 

 tion of about 15 per cent, of the available heat of oxidation. 



Persistent excess of carbohydrate food produces an accumulation of fat, 

 which may not only be an inconvenience causing obesity, but may interfere 

 with the proper nutrition of muscles, produce a feebleness of the action of 

 the heart, and other troubles. 



The formation of fat from protein is discussed on page 436. 



Obesity is a condition of excessive storage of fats. In many of these 

 cases there is persistent storing of fat in the presence of a diet of low energy 

 value and when considerable physical labor is expended. It seems that 

 such persons must have a very economic protoplasmic metabolism, a bio- 

 logical factor that lacks sufficient explanation. 



