Metabolic Effects of Temporally Targeted Food Restriction in Female Rats with or without Estrogen

To lose weight, overweight people limit calories by reducing food intake and/or number of meals, typically eating in the evening when activity is less. We use rats to model this pattern by providing food for 2 hr/day during the inactive period. In previous work, estrogen decreased body weight and food intake during temporally targeted food restriction as it does during ad libitum feeding. Thus, the goal of this study was to investigate mechanisms that underlie estrogen effects on feeding during temporally targeted food restriction. Ovariectomized rats were given estradiol benzoate (EB) or vehicle twice weekly for 3 wks of ad libitum feeding, or for 2 wks of ad libitum feeding followed by 1 wk of access to food for only 2 hr/d. On the last day of food restriction, some rats were allowed to eat before sacrifice (FED) and others were not (FASTED). Rats then were sacrificed to collect blood, livers, adrenals, and uteri. In both hormone groups, 1‐hr food intake increased during targeted food restriction; however EB‐treated rats ate less. Insulin and leptin were reduced in FASTED rats in both hormone groups. Liver glycogen was elevated in ad libitum rats of both hormone groups but decreased in both FED and FASTED food restricted groups. Glucose was reduced, while triglycerides and free fatty acids were elevated in EB‐treated rats that were food restricted. Adrenal weights and plasma corticosterone were greater in EB‐treated rats, but increased in both groups with food restriction, suggesting that temporally targeted restriction is a potent stressor. Together, these results suggest that EB influences metabolic patterns during temporally targeted food restriction, which may contribute to EB effects on eating and body weight during that restriction. Support: OCAST HR12‐196