Dynamics of recovery of body composition after overfeeding, food restriction or starvation of mature female rats

In this study we examined the body composition of rats recovering from overfeeding, underfeeding or starvation. Female rats (220 g) were fed 160%, 100% or 40% of control intake, by stomach tube, until the 40% rats had lost 50 g. Other rats were starved to lose 50 g. Carcass composition was measured on one group from each treatment. The remaining rats returned to ad libitum feeding. The 160% rats were hypophagic and lost weight. Starved and 40% rats were hyperphagic and gained weight. Serum insulin increased with increased food intake. T₄ was depressed by food restriction. T₃ and T₄ increased during weight loss in 160% rats. Carcass composition of rats from each treatment was determined at progressive stages of recovery. Overfed rats had gained 7 g of protein and 43 g of fat. Protein was soon lost but fat was still significantly increased after 44 d of recovery. Starved and restricted rats had lost 11 g of protein and 28 g of fat. Starved rats regained protein earlier than body fat. Restricted rats recovered body fat much earlier than body protein or weight. Body protein and fat may have individual regulatory mechanisms that work together to control body weight.