Increased efficiency of food utilization following weight loss

The efficiency of food utilization following a period of restricted caloric intake was examined under controlled feeding conditions. By restricting caloric intake, the body weight of two groups of rats was reduced to either 92 or 81% of that of an unrestricted control group. For one week, all animals were then fed daily an amount of food equal to their prerestriction intake, adjusted for the intervening change in metabolic mass ($\text{FI}\text{BW}{}_{\mathrm{kg}}{}^{0.75}\text{=}\text{K}$). During this period of realimentation, the control animals gained an average of 1.6 g body weight while ingesting 156.1 g of food. The two restricted groups gained 21.4 g on 154.2 g food and 29.6 g on 140.4 g food, respectively. This inverse relationship between weight gain and food intake provides evidence that underweight animals utilize food more efficiently than do undeprived control animals.