A Three-Meal-a-Day Dietary Pattern Versus Ad Libitum Food Intake in the Albino Rat

Abstract

The hypothesis tested was that rats offered food ad libitum and rats fed three 40 minute meals daily would eat similar amounts of food, but the ad libitum fed rats would store less fat. Fifty-four 70-day old male rats were acclimated to a reverse light-dark cycle for 1 week after which 6 were killed as initial controls. The remaining 48 were fed a diet where 40% of the energy came from fat and carbohydrate, respectively, and 20% from protein. Half of the rats were fed this diet ad libitum and half were fed the diet in three daily meals of 40 minutes duration. Twelve of the rats in each feeding pattern received a diet containing two parts safflower oil for each one part of beef tallow (P:S = 1.5) while the other 12 received a dietary fat with the reverse formulation (P:S = 0.4). Half of the rats fed each diet in each pattern of intake were stressed by immersion in 10° water for 30 seconds daily while the other half remained unstressed. The rats were killed after 120 days, and serum cholesterol and gains in body com ponents were compared with food intake differences. Rats fed ad libitum and those fed three 40 minute meals daily did not differ in fat-free body accumulation, but the ad libitum fed rats consumed 9.5% more energy which was converted to body fat with an efficiency of 50%. The ad libitum fed rats were fatter than rats fed three meals a day. Stress and the P:S ratio of the diet fat had no significant effect on this finding. The hypothesis was tentatively rejected. It would be necessary to extend eating period length of the three-meal-a-day fed rats until they ate the same amount as ad libitum fed rats before the hypothesis could be categorically rejected or accepted. J. Nutr. 108: 1033-1038, 1978.