Body weight change of aged rats on fat option diets

Variability in caloric intake may contribute to compromised nutritional sutus in the elderly, yet mechanisms regulating food intake and body weight in aged groups are poorly understood. This study was designed to determine if aging is associated with a decline in the ability to compensate for alterations in the caloric density of the diet in rats. 3 groups of male F344/BN rats were used:young (3 mo; n=21), middle-aged (MA; 22 mo; n=20), old (30 mo; n=22). After matching for body weight, half of the rats in each group were assigned to a chow-only (C) condition, and half to a limited access fat option (F) condition. All groups had 24-h access to chow (Rodent Diet 5001, PMI Feeds. Richmond, IN) and water. In addition to chow, during weeks 1 and 2 (Phase I) F rats had daily 2-h access to fat (Crisco, Proctor and Gamble, Cincinnati, OH), 3-h prior to lights out. During weeks 3 and 4 (Phase II) 2-h fat access was provided on M, W, F only. 24-h chow and Crisco intakes were measured daily and body weights biweekly. During Phase I, MA and old F rats consumed more calories (p<0.05) and gained more weight (p<0.01) when compared to controls, but not when compared to each other. In Phase II, 24-h food intake patterns differed between F and C rats in each age group, i.e., F rats overate on Crisco days (p<0.05), and undorate on non-Crisco days (p<0.05). Additionally, MA and old F rats lost more weight than controls (p<0.01), but when compared to each other, old F rats lost more weight than MA F rats (p<0.001). These results suggest that fluctuations in the availability of calorically dense foods may impair body weight regulation and contribute to compromised nutritional status in the elderly.