Accuracy of the regulation of caloric ingestion in the rhesus monkey

In seven male monkeys, Macaca mulatta, the infusion of nutrients into the stomach just prior to or 20 h before a 4-h feeding period reduced the feeding by an amount comparable to the calories infused. Pure carbohydrates, fat, protein, and mixtures were employed as infusions and given in a random fashion over a caloric range of 75-300 kcal. In a second series of experiments, monkeys were partially fasted on 1 day and in this way deprived of 75, 150, 300, or 450 kcal. On successive days, they overate to compensate for this deprivation. The smaller deprivations (75 and 150 kcal) were corrected on the first recovery day. The 300-kcal deprivation required 2 days to be corrected while the 450-kcal deficit was only partially restored. These experiments demonstrate the capacities of the monkey to respond with precision to caloric supply and deprivation so as to maintain a constant caloric intake.