The effects of ovarian hormones on regulation of energy balance in Zucker rats

Congenitally obese Zucker rats showed greater food intake, less running in activity wheels and greater body weight and fat content than the normal phenotype. Their food intake, running and body weight did not change significantly with the phase of the oestrous cycle. Ovariectomy had no effect on these variables or on body composition. Oestradiol replacement had little effect. Zucker rats of normal weight, however, showed a normal pattern of responses to the oestrous cycle, ovariectomy and oestradiol administration. The central regulation of energy balance and body weight appear to be insensitive to oestrogens in the obese Zucker rat.