Effects of posture on gastric emptying and satiety ratings after a nutritive liquid and solid meal.

To study the effects of posture and meal structure on gastric emptying and satiety, nine women ingested tomato soup and then immediately or 20 min later an egg sandwich, when seated and when supine. The lag time was not different, but the half-emptying time of the sandwich was 32% longer (P < 0.01) and the emptying rate after the lag phase was 39% slower (P < 0.01) when the subjects were supine than when they were seated. The half-emptying time of the soup was 50% longer (P < 0.01) when the subjects were supine and ingested the soup immediately before the sandwich than in the other three conditions. Postprandial hunger ratings recovered more slowly (P < 0.01) when the subjects ingested the soup 20 min before the sandwich than when they ingested the soup immediately before the sandwich. These results suggest that posture did not affect the intragastric distribution of the sandwich but affected propulsion of the meal into the intestine and that postprandial satiety was enhanced by the cumulative effect over time of a 20-min "head start" in stimulation of intestinal receptors by emptying of the soup.

Rate of intake, bites, and chews-the interpretation of lean-obese differences.

The microstructure of eating behavior reflects physical properties of food. Responses of lean and obese subjects to these physical properties are similar. For example, eating smaller bite-sized food units reduces initial ingestion rate and mean and local ingestion rate for the entire meal, but does not affect total intake in either lean or obese women. On the other hand, analysis of the microstructure of eating behavior also suggests that obese subjects are less hungry and are more motivated by food preferences than lean subjects. For example, in meals of bite-sized food units, initial ingestion rate is less affected by deprivation and more affected by food preference in obese than lean women. In buffet meals with a variety of foods, obese men eat dessert earlier in the meal, and eat more dessert and other energy dense foods than lean men. The research reviewed here suggests that treatments for obesity should not focus on modifying bite size and ingestion rate and other microstructural variables, which are largely determined by the physical properties of food. Instead, treatment should focus on food selection and the stimulatory effects of palatability on intake.

Contribution of gastric and postgastric feedback to satiation and satiety in women.

Two parallel preload studies were conducted to determine the relative contributions of inhibitory feedback from the stomach and intestine to satiation (meal termination) and postprandial satiety. In the Gastric Emptying Study, five normal-weight women each ingested an egg sandwich (307 kcal) (1) immediately after a tomato soup preload (120 kcal), (2) 20 min after a tomato soup preload, and (3) with no preload. There was 125 g more of soup in the stomach when subjects began ingesting the sandwich immediately compared to 20 min after the soup, and the emptying of the sandwich was delayed when it was ingested immediately but not 20 min after the soup. The lag times for emptying of the sandwich were 76.5 (69.1-82.4), 47.2 (20.1-67.7), and 42.4 (17.8-65.1) min for the three conditions, respectively, p < 0.05. In the Food Intake Study, 16 normal-weight women ate significantly less (p < 0.01) in test meals offered immediately (978+/-246 kcal) and 20 min (1027+/-298 kcal) after the soup preload than in a test meal with no preload (1151+/-279 kcal). Despite the different amounts of soup in the stomach, subjects' test-meal intake in the two preload conditions was not significantly different. Subjects' fullness ratings following the preloads and the test meals were not different among the treatment conditions. The results suggest that feedback from neither the gastric nor the postgastric compartment is primary in determining meal size and postprandial satiety. Instead, signals from gastric and postgastric sources are combined to determine meal size and postprandial satiety.

Bioavailability of medication after laparoscopic cholecystectomy.

Bioavailability of medication after laparoscopic cholecystectomy has not been studied previously. There is concern about the ability of patients to tolerate oral medication postoperatively and the optimal timing of hospital discharge. In this study, each subject received 20 mg/kg acetaminophen (po) preoperatively, with a repeat dose at 6 (group 1), 12 (group 2), or 24 h (group 3) postoperatively. Serum levels were obtained 40 and 90 min after each ingestion. Bioavailability of medication was significantly decreased (p < 0.01) 6 h (group 1) and 12 h (group 2) postoperatively. Bioavailability returned to baseline by 24 h after laparoscopic cholecystectomy (group 3). This study indicates that oral medication should be used judiciously during the first 12 h after laparoscopic surgery.

Effects of soup preloads on gastric emptying and fullness ratings following an egg sandwich meal.

To identify the source of inhibitory signals from the stomach or intestine that lead to satiation, the effects of 300-g tomato soup preloads on the gastric emptying of a solid meal and on hunger and fullness ratings were examined. Subjects were nine healthy women who each ingested an egg sandwich: 1) with no soup, 2) immediately after the soup, and 3) 20 min after the soup. Emptying of the sandwich was measured using radionuclide scintigraphy. Soup significantly prolonged the lag phase (period before significant emptying occurred, p < 0.05), and the half-emptying time (p < 0.01) of the sandwich, but only when ingested immediately before the sandwich. Thus, soup affected the emptying of the sandwich when the volume of soup in the stomach was at a maximum. Passage of soup into the duodenum over a 20-min period had no effect on emptying of the sandwich. Despite the different gastric/postgastric distributions of the soup and the sandwich in the two preload conditions, fullness ratings were not different.

Bite size, ingestion rate, and meal size in lean and obese women.

The effect of bite size on ingestion rate, satiation, and meal size was studied in nine lean and nine obese women. On separate days, subjects were given one of three bite sizes of sandwiches and one of two bite sizes of bagels with cream cheese to eat in a laboratory lunch. Decreasing bite size significantly lowered ingestion rate for the whole meal. The effect was most pronounced at the beginning of meals. As bite size decreased from 15 to 5 g, the average ingestion rate decreased from (mean +/- SEM) 19.4 +/- 2.0 to 15.9 +/- 2.0 g/min (p < 0.001). The initial ingestion rate decreased from 30.0 +/- 2.9 to 19.6 +/- 1.7 g/min (p < 0.001). The larger the bite size, the more quickly ingestion rate decelerated; by the end of meals, ingestion rate was not different across conditions. The decrease in ingestion rate with smaller bites was offset by an increase in meal duration, such that meal size did not differ across conditions. Eating behavior of lean and obese subjects was not different. There were individual differences related to ingestion rate, but these were not related to body weight nor to meal size. These results bring into question the recommendation of behavior therapists that obese people eat more slowly in order to eat less.

Effects of variety on food intake of underweight, normal-weight and overweight women.

The food intake of 27 underweight, normal-weight and overweight women was monitored during laboratory luncheon meals of solid food units (SFUs), bite-sized spirals of bread with different sandwich fillings. Simultaneous, but not sequential, presentation of three SFU flavors increased intake compared to presentation of a single flavor in normal-weight and overweight women. Neither variety manipulation enhanced intake in the underweight women, who are more than the other subjects in all conditions. The fact that the foods were so similar probably reduced the effectiveness of the variety manipulations. Overweight and normal-weight subjects had different patterns of intake, but only when eating a single flavor of SFU. Only overweight subjects ate less when three flavors of SFUs were hidden from view in the apparatus used to monitor intake. This procedure prevented subjects from selecting particular flavors of SFUs. Differences in cognitive restraint probably do not explain the differences in the eating behavior of normal-weight and overweight subjects in the present study. Lack of dietary restraint or a high level of hunger may account for the different eating behavior of the underweight subjects compared to the other subjects.

Responses of lean and obese subjects to preloads, deprivation, and palatability.

The effects of preloads, deprivation, and palatability on the eating behavior of non-dieting lean and obese subjects were studied during laboratory meals, using small solid food units (SFUs) to measure the rate of ingestion over the time-course of the meals. In both weight groups, rate of intake decreased from the beginning to the end of meals. The smaller the preloads and the longer the deprivation interval, the faster subjects ate at the beginning of meals and the higher their hunger ratings were. The longest deprivation interval also increased palatability ratings, meal length, and the total amount that subjects ate. Increasing the palatability of the food increased the rate of intake at the beginning of meals, meal length, and the amount of food that subjects ate. Obese subjects were more sensitive to palatability and less responsive to deprivation than lean subjects. For example, while lean subjects became less discriminating about the palatability of the food at the beginning of meals as deprivation increased, obese subjects did not. The satiation mechanism of obese subjects was also different from lean subjects. For example, obese subjects overate after preloads while lean subjects underate compared to their baselines.

Limited weight losses with a gastric balloon.

An evaluation of the Garren-Edwards gastric bubble in the treatment of obesity was done. Several clinical trials have compared the effects of behavior therapy with and without the bubble, but the effects of the bubble alone have not been previously evaluated. Ten obese women averaging 91% overweight received the bubble without adjunctive therapy during a 12-week treatment period. Frequent psychological and laboratory measures as well as weight were obtained during the study to explore the possible mechanisms of the bubble's effect and its side effects. Mean weight change was -2.5 kg, with a range of -8.8 to +1.6 kg. Four patients lost more than 3.5 kg, three lost less than 3.5 kg, and three gained weight. The Garren-Edwards gastric bubble alone does not appear to provide significant benefit to most obese patients.

Effect of naltrexone on food intake, hunger, and satiety in obese men.

Increasing doses of naltrexone (25 to 200 mg) given over 4 consecutive days reduced intake of laboratory luncheon meals by 30% in 17 obese men. Meal size remained suppressed in the laboratory during the week following naltrexone administration. Water intake in the laboratory and body weight were not affected. Rates of ingestion and subjective ratings suggested that naltrexone reduced appetite rather than promoted early satiation. Nausea and other side effects occurred on 1 or 2 days during the naltrexone week in seven subjects whose food intake was reduced. Food intake was also reduced in seven of the remaining 10 subjects who reported no adverse reactions. These results suggest that a conditioned taste aversion or a conditioned anorexia may have developed in some subjects.

Effects of simultaneous oral-intragastric ingestion on meal patterns and satiety in humans.

Simultaneous oral-intragastric ingestion of a liquid diet was compared with oral ingestion for 15-21 days in four males or normal weight, 18-21 years old. All the subjects are significantly more (M= 222 cm3 or kcal [930 kJ] per meal, p less than .025) during simultaneous compared with oral lunches and dinners. Subjects reduced the size and frequency of breakfasts and snacks, which were always ingested orally, however, and did not gain weight. In a second experiment, the same four subjects ate significantly more (M-177 cm3 more, p less than .001 at lunch when the rate of ingestion was 200 cm3/min compared with 100 cm3/min regardless of route (oral, intragastric or simultaneous). They also ate significantly more (M=135 cm3 more, p less than 0.25) during simultaneous meals compared with oral or intragastric meals ingested at the same rate. Thus, rate of ingestion and oral stimulation are important determinants of meal size in humans.