Dynamics of intake suppression after a preload: role of calories, volume, and macronutrients

Twenty-four-hour cumulative food intake is the summation of repeated bouts of feeding, separated by intermeal intervals. Intake in a given meal influences subsequent feeding by modulating the duration of the intermeal interval, meal size, or both. Analysis of the time course of the effect of an individual meal on subsequent feeding may therefore clarify the controls of meal patterning and 24-h intake. In the present experiments, rats consumed a preload and then ate a test meal ad libitum. With the length of the preload-to-test meal interval varied from 10 to 180 min, the time course of the impact of various preloads on meal size was revealed. The main findings were the following: 1) caloric content, rather than volume, was the primary determinant of the intake-reducing effect of a glucose preload; 2) no differences in the time course of intake reduction were found after isocaloric preloads of fructose, glucose, and sucrose; 3) a fat preload attenuated subsequent intake less than an isocaloric sucrose preload; and 4) a short-lived (< 20 min) effect of sensory-specific satiety was evident. These findings are consistent with what is known about long-term effects of dietary manipulations on 24-h intake. Because daily intake reflects multiple iterations of feeding followed by an intermeal interval, a focused study of the duration of the impact of meals on subsequent ingestion may clarify the relationship between controls of individual meals and 24-h food intake.