Interactions between postprandial thermogenesis, sensory stimulation of feeding, and hunger.

An early thermogenic response has been described following the ingestion of palatable food. This study was designed to investigate the possible relationship between this so-called cephalic response, the sensory stimulation of feeding, and the declining feeling of hunger as the meal progresses. O2 consumption, carbohydrate and lipid oxidation, as well as ratings of hunger were measured in four experimental situations in which the subjects, after overnight fast, ate either two small caramel cakes at one time or the same amount of calories divided in eight portions that were eaten at 10-min intervals. The third experiment, the sham-feeding experiment, was similar to the last one except that the food was spit out instead of being swallowed after being chewed. A control experiment was added in which no food was given but during which the subject mimicked the act of chewing as was done in the preceding experiment. A small increase in O2 consumed was observed in the control experiment. After the one-meal experiment, the increase was larger for the first 90 min and declined thereafter. During the first 40 min of the sham-feeding experiment, O2 consumption increased more than when the eight meals were eaten, indicating that during this period the sensory stimulation per se is responsible for the cephalic thermic response to food. At 90 min, the ratings of hunger were diminished not only in the eight meals experiment but in the eight sham meals experiment as well, showing the role of sensory stimulation in the control of hunger. These results indicate a possible causal relationship between the cephalic thermogenesis, the control of hunger, and the prandial sensory stimulations.