Gastric emptying of glucose and nutrient energy in meal-fed rats.

Male rats (designated "meal-feeders") were trained for at least 21 days to eat voraciously for 2 hour a day a high-glucose, nutritionally adequate diet, while "nibblers" were fed the same diet ad libitum. In experiment 1, a second control group received the same amount of diet as eaten by meal-feeders but in four meals per day. Final test meals comprised either 10g per (kilogram body weight)3/4 or all that the animal would eat in a 2-hour period. With both sizes of test meal, gastric emptying of fat and/or glucose was greater in meal-feeders than in either control groups. In experiment 2, gastric emptying of glucose and fat was measured in meal-feeders and nibblers during three intervals of the dark period and during the 12-hour light period. An unusually rapid gastric emptying of glucose and of metabolic energy was observed in meal-feeders but was confined to the early period after the start of the daily meal. Glucose was emptied preferentially to fat under all test conditions. This tendency was prominent, however, only when a small meal was fed or after stomach contents had declined.