Intake and weight adjustments in rats to changes in feeding schedule.

Abstract

This study has recorded the adjustments in food intake and weight that occurred when subgroups of 34 albino rats were repeatedly shifted from ad lib feeding to a 22-hr. deprivation schedule and conversely. When these Ss were shifted from the ad libitum feeding to the 22-hr. deprivation schedule, there was a 7-10 day period during which Ss gradually increased their intake, although weight decreased. When these Ss are returned to ad libitum feeding, there is a comparable period of readjustment during which they "overeat" with a gradual decrease in intake to a new level, but with a corresponding acceleration in weight. These data also suggest that the first of these adjustments, either from the ad libitum to the deprivation condition or conversely, occurs more slowly than do later ones. This tends to be in keeping with the hypothesis that these adjustments represent in part a period of learning to eat in response to changed internal and external cues. However, there is no clear evidence that this increase in the rate of adjustment continues with repeated experiences of this type. But as a test of the learning hypothesis, these data are contaminated by the fact that Ss continually increased in average weight. If the rate of adjustment is a joint function of physiological factors, such as those mirrored by changes in weight, and learning, the influence of the latter would be obscured by the progressive change in weight.