842 XIV. NUTRITIONAL VALUE OF FATS 



category has been that of Hoagland, Snider, and Swift,^^ who reported 

 that they were unable to demonstrate any statistical difference in the gains 

 of weight, storage of fat or protein, or the efficiency of utilization of feeding 

 energy in rats on diets containing 4, 9, or 14% of fat (5.0, 10.98, or 18.27% 

 of the calories, respectively). The most recent results of French and his 

 collaborators-* have confirmed the fact that identical growth can be 

 brought about in male and female rats on a high-fat diet (22.7%), and on a 

 low-fat I'egimen (3.4%). The difference in food consumption amounted 

 to 4.8% and 5.7% less total calories consumed on the high-fat diet for 

 males and for females, respectively. The preponderance of evidence, 

 therefore, would seem to favor the hypothesis that greater increases in 

 weight, and improved efficiencies of the diet, are associated with fat con- 

 sumption in the rat. Siedler and Schweigert-^ reported that the rates of 

 gain of cocker spaniel pups when 4, 6, or 8% of fat was added to the basal 

 diet, or when 6% of fat was added to commercial meal, were equal or 

 superior to those obtained when no fat was added. No significant differ- 

 ences in the food or caloric efficiency were noted between groups fed 

 different levels of fat, indicating that the calories from fat were well 

 utilized. 



b. Associative Dynamic Action. The greater gain in weight observed 

 by many different investigators for rats on isocaloric diets containing 

 generous proportions of fat, as compared with weight gains in animals on 

 low-fat regimens, is best accounted for by differences in the specific dy- 

 namic action exerted by the fat under these conditions. This variation in 

 the effect of the fats, which was first discovered by Forbes and Swift, ^^ 

 and which has been termed "Associative Dynamic Effect," may be ex- 

 plained by the fact that the increased growth of animals on a high-fat 

 diet represents an accumulated saving of calories due to the fact that 

 smaller amounts of waste energy are lost, as a result of specific dynamic 

 action. This saving can be reflected in the calories utilized for growth 

 instead of for heat production. 



It has long been recognized that respiratory metabolism is increased 

 above the basal level during the period of absorption, transport and inter- 

 conversion of the foodstuffs in the animal body. This increase in metab- 

 olism over and above the normal basal rate is termed specific dynamic 

 action. On the basis of caloric intake, protein exerts the greatest stimula- 



23 R. Hoagland, G. G. Snider, and C. E. Swift, /. Nutrition, 47, 399-409 (1952). 



24 C. E. French, R. H. Ingram, J. A. Uram, G. P. Barron, and R. W. Swift, J. Nutri- 

 iion, 51,329-339 (1953). 



2ft A. J. Siedler and B. S. Schweigert, J. Nidritioii, 48, 81-90 (1952). 

 26 E. B. Forbes and R. W. Swift, /. Nutrition, 27, 453-468 (1944). 



