712 PHYSIOLOGY 



the nitrogen output during starvation, carbohydrate food causes a 

 diminution in the nitrogen output, and thus exercises a marked 

 sparing effect on the proteins of the body. Voit found that during 

 starvation or with an insufficient protein diet addition of fat to the 

 food increased the total metabolism. When sufficient protein was 

 being supplied, the addition of fat caused no increase in the total 

 metabolism, the whole of the fat in the food being laid on as fat in 

 the body. The stimulating effect of fat on metabolism is but slight. 

 Magnus Levy found that the increase in the metabolism on the 

 administration of fat to a starving animal was minimal and never 

 exceeded 10 per cent. 



Carbohydrates have a somewhat greater influence on meta- 

 bolism. The administration of a large meal of carbohydrates to a 

 starving animal may raise the respiratory exchanges from 20 to 

 30 per cent., and the increase may last four hours after the meal. 

 This stimulating influence on metabolism is, however, much less than 

 that observed on the administration of large doses of protein. If 

 carbohydrate be given in excess of the daily energy requirements 

 the greater proportion of it remains in the body, being stored up to 

 a small extent as glycogen, but mainly in the form of fat. 



