Deprivation, weight loss and intake in the rat as a function of age: Evidence for an obligatory growth factor

Groups of rats covering a range of ages were deprived of food, water, or both food and water. The percentage weight loss in all groups was found to be well approximated by a simple power function of deprivation time, with the exponent being relatively independent of the age of the animals or the kind of deprivation. However, younger animals lost weight at a faster rate than older ones and were more affected by food deprivation than by water deprivation. Several aspects of the data suggest that young animals are subject to an obligatory growth factor that produces a disproportionately greater debilitation when they are food deprived.