SOURCES OF FAT IN ANIMAL BODY 539 



as determined by balance experiments has been confirmed in the goose 106 

 and in the dog. 107 



A second method, also indirect, by which this thesis has been proved, is 

 based upon the fact that an elevation of the Respiratory Quotient (R.Q., 

 i.e., volume of respiratory CCVvolume of respiratory O2) occurs over a 

 considerable period following the ingestion of large amounts of carbohy- 

 drate. This phenomenon is to be observed during the interval when a 

 conversion of carbohydrate to fat is presumably taking place. For a 

 discussion of the R.Q. and its implications, see the review of Richardson. 108 



When carbohydrate is completely oxidized to carbon dioxide and water, 

 the R.Q. is 1.00. However, when an oxygen-rich foodstuff such as carbo- 

 hydrate is converted to an oxygen-poor foodstuff such as fat, extra oxygen 

 is available for metabolic purposes; accordingly, less oxygen need be ab- 

 sorbed, and the R.Q. for this reaction will exceed 1 .00. In fact, Bleibtreu, 109 

 as cited by Lusk 110 calculated that the theoretical R.Q. for the conversion 

 of carbohydrate to fat is 8.00. The postulated reaction for this change is: 



4C 6 H 12 6 + Oo > C 16 H 32 2 + 8CO2 4- 8H 2 



Glucose Palmitic acid 



However, since a certain amount of carbohydrate continues to be com- 

 pletely oxidized to furnish energy, with a resultant R.Q. of 1.00, and pro- 

 tein must likewise be metabolized to supply the body needs (R.Q. = 0.801), 

 the observed R.Q. of the animal during the process of fat synthesis never 

 approaches the theoretical value of 8.00. The resultant R.Q. will be the 

 sum of the R.Q.'s of the myriad of reactions taking place concomitantly. 



According to a number of reports in the literature, the respiratory quotient 

 under these conditions actually does exceed 1.00. Bleibtreu 109 observed a 

 ratio of 1.33 in a goose which was stuffed with carbohydrate, although when 

 the animal was fasted the R.Q. was only 0.73. Under the latter circum- 

 stances, fat was largely oxidized; this foodstuff has an R.Q. of 0.707. A 

 ratio of respiratory carbon dioxide to respiratory oxygen of 1.39 has been re- 



106 K. B. Lehmann and E. Voit, Z. Biol, /& [n.s. 24), 619-671 (1901). 



107 M. Rubner, cited by G. Lusk, The Elements of the Science of Nutrition, 4th ed., 

 Saunders, Philadelphia-London, 1928, p. 395. 



108 H. B. Richardson, Physiol. Revs., 9, 61-125 (1949). 



109 M. Bleibtreu, Arch. ges. Physiol. (Pfliiger's), 85, 345-400 (1901). 



110 G. Lusk, The Elements of the Science of Nutrition, 4th ed., Saunders, Philadelphia- 

 London, 1928, pp. 206, 275, 396-398. 



