Role of food intake in estradiol-induced body weight changes in female rats

In two experiments, we examined the relationship between estradiol-induced undereating and body weight loss in ovariectomized (OVX) rats. In the first experiment, both estradiol benzoate (EB) and the nonsteroidal anti-estrogen, MER-25, produced body weight losses that could not be duplicated simply by pair-feeding. In the second experiment, we compared the effects of EB treatments in obese OVX rats and in OVX rats in which the post-OVX obesity was prevented by food restriction. When fed ad libitum, both groups of oil-treated OVX rats exhibited substantial body weight gains that were not accompanied by overeating. In lean OVX rats, EB treatments caused a transient hypophagia but did not reduce body weight. These results suggest three conclusions. (1) Changes in food intake are neither necessary nor sufficient to cause some of the body weight changes induced by ovarian hormones. (2) Estradiol can depress food intake in female rats without altering the regulated body weight. (3) More attention should be paid to metabolic factors when studying gonadal influences on body weight.