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 normal volunteers were studied on four occasions, on each of which a meal comprising ground beef mixed with tomato sauce of either 650 g ("large") or 217 g ("small") was eaten. Two studies were performed while the subject was lying in the left lateral decubitus position, and two studies were performed while the subject was sitting so that in each subject data were available for both meals and in both postures. Hunger and fullness were evaluated using a visual analog questionnaire. In both postures and after both meals, gastric emptying approximated a linear pattern after an initial lag phase. The lag phase was shorter for the 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 greater 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 rapid 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 between 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 volume and posture between the four studies and demonstrated an effect of 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 the 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 large meal. We conclude that meal volume has a major effect on gastric emptying; in contrast posture has only a minor impact on intragastric meal distribution, which is observed only after a large meal, and no effect on gastric emptying.