EFFECTS OF MEAL VOLUME AND POSTURE ON GASTRIC-EMPTYING OF SOLIDS AND APPETITE

The effects of volume and posture on gastric emptying and intragastric distribution of a solid meal and appetite were evaluated. Eight norma l volunteers were studied on four occasions, on each of which a meal c omprising ground beef mixed with tomato sauce of either 650 g (''large '') or 217 g (''small'') was eaten. Two studies were performed while t he subject was lying in the left lateral decubitus position, and two s tudies were performed while the subject was sitting so that in each su bject data were available for both meals and in both postures. Hunger and fullness were evaluated using a visual analog questionnaire. In bo th postures and after both meals, gastric emptying approximated a line ar pattern after an initial lag phase. The lag phase was shorter for t he large meal when compared with the small meal [sitting: large 13 +/- 5 vs. small 29 +/- 7 min; left lateral: large 16 +/- 3 vs. small 24 /- 3 min, F(1,7) = 46.3, P < 0.0005]. In both postures the contents of the total [F(1,7) = 1794.5, P < 0.0001], proximal [F(1,7) = 203.7, P < 0.0001], and distal [F(1,7) = 231.5, P < 0.0001] stomach were greate r after the large meal when compared with the small meal. Although the 50% emptying time was greater with the large than the small meal [F(1 ,7) = 40.8, P < 0.001], the postlag emptying rate (g/min) was more rap id with the large meal [sitting: large 1.7 +/- 0.2 vs, small 1.1 +/- 0 .1 g/min; left lateral: large 1.8 +/- 0.1 vs, small 1.3 +/- 0.04 g/min , F(1,7) = 44.7, P < 0.0005]. There was a significant interaction betw een meal volume and posture for retention in the distal stomach [F(1,7 ) = 7.14, P < 0.05]. Contrasts were used to evaluate the effects of vo lume and posture between the four studies and demonstrated an effect o f posture for the large [F(1,21) = 18.7, P < 0.005] but not the small [F(1,21) = 0.30, P = 0.60] meal so that the retention was greater in t he sitting when compared with the left lateral position. The magnitude of the postprandial increase in fullness [F(1,7) = 7.8, P < 0.05] and reduction in hunger [F(1,7) = 5.9, P < 0.05] was greater with the lar ge meal. We conclude that meal volume has a major effect on gastric em ptying; in contrast posture has only a minor impact on intragastric me al distribution, which is observed only after a large meal, and no eff ect on gastric emptying.