CONVERSION OF FAT TO CARBOHYDRATE 227 



for R.Q. cited in the literature, in reports from laboratories in which the 

 analytical technic could not be questioned. 



A large proportion of the low ^•alues were obtained in the case of dia- 

 betics; R.Q. values as low as 0.669 for such patients can be justified on 

 theoretical grounds, without the necessity of assuming a transformation of 

 fat to carbohydrate or of an inaccuracy in determination. Thus, if one ex- 

 cludes from the calculation the proportionate amount of carbohydrate 

 formed from protein (since this is not oxidized in the diabetic), the revised 

 protein R-Q.'"" becomes 0.632 instead of 0.802. Magnus-Levy^"^ estimated 

 the R.Q. of the protein -^ carbohydrate conversion as 0.613, while Geel- 

 muyden^"- proposed a figure of 0.706. The R.Q. of fat is likewise altered in 

 diabetes, since a complete combustion does not obtain due to the attendant 

 ketonuria. According to Allen and DuBois,^^ and Magnus-Levy,^"^ the 

 normal R.Q. of fat, 0.707, would be reduced to 0.669 if the jS-hydroxybutyr- 

 ate were not metabolized.- If more than one molecule of ketone bodies were 

 formed from one molecule of long-chain fatty acid,^^ the R.Q. would be re- 

 duced to a still greater extent, below 0.669. An upset of acid-base balance 

 in the blood and tissues would probably further complicate the calculation 

 of the R.Q. in diabetes. 



Hawley, Johnson, and Murlin^"^ ha\'e suggested another interesting pos- 

 sibility to explain the low R.Q. during the earl}^ period of fat metabolism, 

 which might very well occur normally. Thus, in the oxidation of the fatty 

 acid chains, if desaturation proceeded rapidly and was not accompanied by 

 a rapid completion of the oxidation, absorption of oxj^gen to oxidize the 

 hydrogens removed might occur without a concomitant production of car- 

 bon dioxide. This would result in a reduced R.Q. during the period when 

 this part of the reaction was the predominant one. This as offered is a pos- 

 sible explanation for the low values obtained in human subjects before they 

 have become adjusted to a high-fat diet. Werthessen ^"^ reported wide varia- 

 tions in the respiratory quotient of rats over a twenty-four-hour period, 

 ranging from 0.27 to L70, when the animals were fed their total twenty- 

 four-hour requirement within a period of one to five hours. Similar results 

 were obtained by MarkoAvitz,^"^ using himself as subject. Soskin^" de- 



i"' G. Lusk, Arch. Internal Med., 15, 939-944 (1915). 



i"! A. Magnus-Levy, Arch. Anat. Physiol, 1.904, 377-382; Z. kiin. Med., 56, 83-99 

 (1905). 



102 H. C. Geelmuyden, Ergeh. Physiol, 21, No. I, 274-360 (1923); 22, 51-298 (1923). 



i»3 E. E. Hawley, C. W. Johnson, and J. R. Murlin, /. Nutrition, 6, 523-557 (1933). 



10^ N. Werthessen, Am. J. Physiol, 120, 458-465 (1937). 



»"« J. Markowitz, unpublished results cited bv S. Soskin, Physiol Revs., 21, 140-193 

 (1941), p. 153. 



