Dietary influences on gastric emptying of carbohydrate versus fat in the rat.

The degree to which the rat stomach empties carbohydrate in preference to fat was studied in rats fed a diet or various test means providing carbohydrate and fat in a 3:1 (w/w) ratio. When rats were adlibitum fed a glucose-containing diet, the glucose:fat ratio in gastric contents was consistently lower than in the diet and was 10% as great at noon as at midnight. When starved rats were fed a single meal of the same diet the average fractional emptying rate for carbohydrate exceeded that for fat; and the ratio of these rates ("the gastric emptying ratio") was essentially the same when calculated from gastric contents observed 1, 2, 4, or 6 hours after the test meal. The gastric emptying ratio was also not changed when test means were made with hard, soft, or liquid fat or with no or extra protein (lactalbumin). Use of finely divided glucose monohydrate, dried crystalline glucose or of cornstarch resulted, respectively, in high, intermediate and low gastric emptying ratios. The kind and form of carbohydrate in the meals and the ease of its extraction with water appear to be important factors governing the degree to which carbohydrates is preferentially emptied from the stomach.