Body weight set-point changes during the ovarian cycle: experimental study of rats using hoarding behavior.

Body weight, food intake and food hoarding behavior were measured in 12 female rats fed ad lib and correlated with the ovarian cycle of each. All three parameters fluctuated synchronously, being minimal at estrus and maximal at diestrus. The hypothesis was then tested that these fluctuations result from cyclical oscillation of the body weight set-point entrained by the ovarian cycle, as previously proposed by others. The linear correlation between hoarding behavior and body weight was used to extrapolate the computed threshold of body weight at which hoarding behavior occurred at diestrus and at estrus; this threshold has already been shown to be a good index of the body weight set-point. The results indicated that the regression of hoarding behavior on body weight was virtually identical at estrus and diestrus (same slope), but the critical level of body weight for the onset of hoarding behavior was 31.2 g lower at estrus than at diestrus. This provides direct evidence in the rat of fluctuation of the body weight set-point with the ovarian cycle.