Regulation of food intake in monkeys: response to caloric dilution.

HANSEN, B. C., K.-L. C. JEN AND P. KRIBBS. Regulation of food intake in monkeys: Response to caloric dilution. PHYSIOL. BEHAV. 26(3) 479--486, 1981.--Ability to regulate level of energy intake was studied in adult rhesus monkeys (Macaca mulatta) using calorically diluted diets. Twenty-four hour access to a complete liquid diet was provided via leakproof gravity feeders. The addition of water provided 4 caloric concentrations over the range of 0.5 to 1.35 kcal/ml. Average caloric intake per kg body weight was 84 _+ 0.7 kcal/kg (mean _+ SE). Seven of the eight monkeys maintained a constant caloric intake by adjusting oral intake in response to randomly ordered but sustained changes in caloric density. One monkey ingested a significantly higher caloric load while receiving the highest density diet. Rates of compensation for dilution following each diet change varied widely, occurring over periods of 3 days to 2 weeks. It was concluded that individual monkeys vary significantly in the rate of adjustment to caloric dilution, and thus long term studies must be used in studying controls of feeding in monkeys.