Effects of palatable diets on body weight and adipose tissue cellularity in the adult obese female Zucker rat (fa/fa).

Obese 7-8 mo-old female Zucker rats (fa/fa) and their lean littermates (Fa/-) exhibited the same percentage increase in body weight during a 50-day period when both groups of animals were fed a highly palatable snack food diet (SF). A subsequent 50-day period of refeeding with standard laboratory chow caused rats of both genotypes to shed the excess weight gained on SF. These findings suggest that lean and obese Zucker female rats are comparably responsive to a highly palatable diet. When a second group of female fa/fa rats were fed either SF or another palatable, semipurified high fat diet for 135 days, beginning at 2-3 mo of age, they were found to have substantially more fat cells in all depots studied than did female (fa/fa) rats that had been fed only chow. Thus, the obese Zucker rat is also comparable to normal rats with respect to the phenomenon of diet-induced adipocyte hyperplasia.