Relative contributions of intestinal, gastric, oro-sensory influences and information to changes in appetite induced by the same liquid meal

To investigate the contribution of oral, gastric and intestinal factors in the control of appetite, 425 ml (400 kcal) tomato soup was administered either orally, intragastrically (covertly and overtly) or intraduodenally (overtly) to nine healthy, fasted, male volunteers. Ratings of fullness, hunger and desire to eat were recorded over a period of 2 h and gastric emptying was measured after soup fed orally and intragastrically. Infusion of the soup into the small intestine at a rate commensurate with normal gastric emptying exerted no significant suppression of ratings of hunger and desire to eat and no significant production of fullness. Covert, intragastric infusion of the same soup suppressed appetite and this suppression was increased when the subjects were informed of the nature of the infusion, but there were no differences in gastric emptying profiles between covert and overt intragastric infusions of soup. Oral administration of the soup produced the greatest suppression of appetite compared with other conditions and also generated a slower rate of gastric emptying compared with both intragastric soup infusions. Strong correlations were observed between appetite ratings and both gastric and intestinal contents following intragastric infusions of the soup meal and these were enhanced following oral administration of soup. These results indicate how information, orosensory, gastric and intestinal factors can interact to elicit optimal expression of fullness and suppression of hunger. Specifically, the data not only demonstrate how the influence of gastric distension appears to overwhelm any direct influence of intestinal chemostimulation on appetite and how information modulates this effect, but the data also support an important role in appetite suppression for psychophysiological mechanisms stimulated by orosensory mechanisms. (C) 1998 Academic Press.