Orexigenic and obesity effects of estrogen deficiency can be attenuated by half‐day food deprivation either during the light phase or the dark phase

Estrogen deficiency enhances food intake, especially during the light phase, and also body weight gain. In the present study, we examined the effect of food deprivation during the light phase and the dark phase on the estrogen deficiency‐induced enhancement of daily food intake and body weight gain. Ovariectomized rats were assigned into the estrogen (E2)‐treated or vehicle (Veh)‐treated group. Rats were then fed ad libitum or with food deprivation either during the light phase or the dark phase. At the end of the experiment, we examined the number of c‐Fos, Bmal1 and Per1 reactive cells in the SCN during the light and dark phases. Daily food intake, total food intake over 2 weeks and body weight gain were not affected by the diurnal food deprivation in the E2 group, but these were attenuated in the Veh group. Food deprivation during the dark phase reduced daily food intake and body weight gain in the both of E2 and Veh groups compared with ad lib feeding, the decrease was larger in the Veh group than the E2 group, and daily food intake became similar between the groups. Expressions of c‐Fos and Bmal1 in the SCN were not significantly different between the two groups either during the light or dark phase. These data indicate that orexigenic effect of estrogen deficiency can be abolished by half‐day food deprivation either during the light phase or the dark phase, and the SCN is not likely involved in the regulations of daily food intake and body weight in response to the half‐day food deprivation.