TRIGLYCERIDES AND FATTY ACIDS 159 



which arises is whether the Eskimos are inherently less susceptible to keto- 

 sis, or whether they ha^'e become adapted to a meat diet. In the year-long 

 experiment carried out in the case of the white Arctic explorers, who 

 consumed only a meat diet, McClellan and DuBois^^* noted that an 

 apparent adaptation to the diet obtained, inasmuch as the ketonuria 

 tended to diminish after several months on the carbohydrate-free diet. 



Samuels and co-workers^^^ demonstrated that the spontaneous and forced 

 activity exhibited by fasting rats, as well as the duration of survival, are 

 related to the prefast diet. Marked increase in survival time, and in the 

 amount of work performed before exhaustion, were observed in the case of 

 rats receiving fat diets as contrasted with those on carbohydrate or protein 

 diets. Roberts and Samuels*^'' reported that the rats Avhich had been given 

 a high-fat diet exhibited a lower susceptibility to insulin injection than 

 did animals previously fed a high-carbohydrate regimen. This resistance 

 to insulin by the fat-fed group was found to be ascribable to the sparing 

 action of the diet on liver glycogen."^'^^^ Even in the case of hepatecto- 

 mized rats, the animals previously conditioned to fat survived about twice 

 as long after the operation as did animals previously conditioned to carbo- 

 hydrate. ^^^ Gilmore and Samuels'*^" carried out experiments with isolated 

 tissues; they noted a lower rate of glucose utilization when the rats had 

 received a high-fat diet than was the case when they had been fed on a 

 high-carboh.ydrate regimen. Lundbaek and Stevenson ^^^ observed that the 

 rate of glucose utilization in vitro by the diaphragm of fat-fed rats was 

 only approximately one-half of that of carbohydrate-fed animals, when the 

 tissues were immersed in glucose solution. 



El Rawi and Geiger'*^^ demonstrated that adaptation to a fat diet 

 develops in rats fed a diet containing 15% protein and the balance largely 

 composed of fat, as contrasted with one containing chiefly carbohydrate. 

 Not only were the fat-adapted rats able to maintain higher li^^er glycogen 

 and blood-sugar levels during subsequent fasting, but they were likewise 

 found to be more resistant to insulin. It would therefore seem probable 

 that the body accommodates itself to different dietary regimens by the 

 development of diverse • enzyme systems for carrying out the catabolism 



«« L. T. Samuels, R. C. Gilmore, and R. M. Reinecke, J. Nutrition, 36, 639-651 (1948). 



«'S. Roberts and L.' T. Samuels, Proc. Soc. Exptl. Biol. Med., 53, 207-208 (1943). 



*™ L. T. Samuels, R. M. Reinecke, and H. A. BaU, Proc. Soc. Exptl. Biol. Med., 49, 

 456-458(1942). 



"^ S. Roberts, L. T. Samuels, and R. M. Reinecke, Am. J. Physiol, 140, 639-644 

 (1944). 



*8» R. C. Gilmore, Jr., and L. T. Samuels, J. Biol. Chem., 181, 813-820 (1949). 



*^^ K. Lundbaek and J. A. F. Stevenson, Federation Proc, 7, 75 (1948). 



^* I. EI Rawi and E. Geiger, unpublished results, 1953. 



