840 XIV. NITTRITTOXAL VALUE OF FATS 



tlie dominant factor up to the last period investigated, namely, nine to 

 twelve weeks, at which time the greatest potentiality for growth was still 

 exhibited by the animals whose diet contained generous quantities of fat. 

 In another series of tests which were carried out by Scheer et al?^ on young 

 adult rats, it was found that the loss of weight by the rats, when subjected 

 to severe caloric restriction, was less in the groups receiving the high-fat 

 diets than in those receiving the isocaloric low-fat diets. Moreover, the 

 mortality rate observed in rats receiving the high-fat diet during the period 

 of caloric restriction was much less than the figure obtained for those on 

 the low-fat regimen. Finally, when the depleted animals were again 

 allowed to replete on the same diets, but given ad libitum, those animals 

 which were receiving the high-fat rations made a much better recovery 

 during the subsequent period than did those which were on the low-fat 

 diets. This gain was due to fat rather than to the essential fatty acids 

 contained, as is shown by the experiments of Pearson and Panzer, ^^ which 

 demonstrated that rats fed a diet containing 8% of corn oil or lard dd 

 libitum gained 29% more in body weight than did animals which were 

 maintained on a similar diet minus the fat but with the addition of ethyl 

 linoleate. In general the fat content of the body is not closely related to 

 the fat content of the diet. Thus it was shown by Scheer and colleagues^'' 

 that rats receiving 20% of fat in the diet, rather than those receiving 40%, 

 had the highest content of body fat. It was calculated in these experi- 

 ments that the greater body size of animals on diets containing liberal 

 amounts of fat, as compared with fat-free diets, is not solely the result of 

 deposition of fat. It would thus appear from the experiments carried 

 out employing ad libitum feeding that animals do better on high-fat diets 

 than when a low-fat regimen is employed. However, these data do not 

 answer the question whether or not improved body weights are to be as- 

 cribed to the fact that the animal is able to consume a larger proportion 

 of calories on the higher fat diets than on the lower fat diets, or whether 

 some other condition is responsible for the better growth. 



Lundbaek and Stevenson"^ observed greater weight gains in rats on a 

 high-fat, non-carbohydrate diet than on diets high in carbohydrate. A 

 greater efficiency of utilization of the calories was noted on high-fat diets. 

 These workers advanced the hypothesis that this greater efficiency was 



16 B. T. Scheer, J. F. Codie, and H. J. Deuel, Jr., /. Nutrition, 33, 641-648 (1947). 

 16 P. B. Pearson and F. Panzer, J. Nutrition, 38, 257-265 (1949). 

 " B. T. Scheer, E. Straub, M. Fields, E. R. Meserve, C. Hendrick, and H. J. Deuel, 

 Jr., /. Nutrition, 34, 581-586 (1947). 



i7» K. Lundbaek and J. A. F. Stevenson, Am. J. Physiol., 151, 530-537 (1947). 



