Evidence that the amount of food consumed in early life fixes appetite in the rat.

Rats were raised in litters of 22 (low caloric intake) or litters of 4 (high caloric intake). At the end of 62 wk, rats from large litters were approximately 140 g lighter than those from small litters even though all animals were permitted unrestricted access to food after weaning. One factor responsible for the smaller body size was a lower voluntary food intake after weaning (8,188 +/- 205 g vs. 9,808 +/- 193 g; P less than 0.001). These results provide evidence that the amount of food consumed during suckling plays an important role in determining the habitual food intake of rats in later life. In a separate experiment, rats were raised in litters of 4, 13, 17, or 22. The results show that as litter size increased from 4 to 22, a corresponding reduction in the voluntary intake of food occurred. These results provide evidence that by controlling the food intake of the newborn rat it is possible to "program" the animal for a desired voluntary food intake in later life.