Effect of a soup preload on reduction of food intake by cholecystokinin in humans.

Cholecystokinin octapeptide (CCK-8) or saline was intravenously infused for 5 min before and 5 min during a meal of macaroni and beef, served 20 min after a preload of either 100 or 500 g of soup to 12 nonobese men. Intake of the test meal was significantly lower when CCK-8 was given, following the larger preload, than after any of the other treatments. There were no significant differences among the other three treatment conditions. These results are consistent with the hypothesis that gastric, but not merely pregastric, stimulation interacts with CCK-8 to reduce food intake in humans. Although gastric filling seems to be the most likely stimulus for the interactive effect with CCK-8, other factors such as activation of nutrient-sensitive sites cannot be eliminated. In addition, hunger ratings were significantly lower immediately after the larger soup preloads than after the smaller. Hunger ratings after the soup also correlated better with test-meal intake after the large soup preloads with and without CCK-8 than after the smaller preloads. Hunger did not correlate significantly with test meal intake after the small soup preload with CCK-8. These results suggest that hunger ratings are more sensitive predictors of intake when the stomach is relatively full (i.e., after a large preload) than when it is relatively empty (i.e., after a small preload) at the time the hunger rating is taken.