Consequences of Restricted Feeding/Refeeding Cycles in Lean and Obese Female Zucker Rats

Abstract

Lean and obese female Zucker rats underwent four, 6-wk cycles of restricted feeding/refeeding. Restricted-fed, lean (RL) rats lost and then regained sufficient weight in each cycle to weigh the same amount as ad libitum-fed, lean (AL) rats at the end of each refeeding period. After the final period of restricted intake, RL rats had significantly lower parametrial and retroperitoneal pad weights and fat cell sizes than AL rats, but their organ growth and lipogenic enzymes were not affected. After the final refeeding period, there were no differences between RL and AL rats except in cumulative food intake. During the first period of restricted intake restricted-fed, obese (RO) rats did not lose weight; however, they were unable to attain the body weight of ad libitum-fed, obese (AO) rats during the subsequent refeeding period. In later cycles, RO rats lost and regained weight, but always weighed significantly less than AO rats. Following the final restricted feeding and refeeding periods, fat pad weights and cell numbers were significantly lower in RO than AO rats, but fat cell size was not affected. Liver weight and lipogenic enzymes were lower in RO than in AO rats after the final period of restricted intake, but were similar to AO rats after the final refeeding period. Permanent effects on heart and kidney growth were found in RO rats. Obese rats appeared to respond differently than lean rats to this form of dietary intervention.