The effect of increased adiposity on food intake of juvenile rats

The regulation of feeding by body adiposity, as proposed by the lipostatic theory, has been well demonstrated in adult animals. However, mechanisms controlling long-term feeding in juvenile animals have not been well defined. In this study, increased adiposity was induced in young rats through oral gavage. Four-week-old rats were divided into three groups; ad lib feeding (100%-AL), tubefed 100% (100%-TF) or 150% (150%-TF) of ad lib intake. Animals were tube-fed these levels for one week. At the end of this period, one third of each group were killed and all remaining animals were returned to ad lib feeding for either 4 or 29 days later. During this recovery period, the 150%-TF group had significantly depressed food intakes for the first 4 days in comparison to the 100%-TF group. Afterwards, there were no significant differences between these two groups for the remainder of the study. Overfeeding induced significant increases in total body fat in the 150%-TF group (24.8 grams) in comparison to the 100%-AL group (11.0 grams) and the 100%-TF group (14.0 grams). By day five of recovery, only the 150% group exhibited a significant loss of body fat. Total carcass protein and ash were not different between groups at any period. At day 29 of recovery, there were no treatment differences in carcass weight or fat content. Loss of body fat from the 150%-TF rats was associated with the decline in caloric intake. It appears that food intake is affected by relative adiposity during the dynamic phase of growth.