Effects of xylitol on gastric emptying and food intake

We studied the effects of xylitol, the pentose-sugar alcohol, on gastric emptying of the solid-food component of a complex meal. Gastric emptying was measured in human volunteers by utilizing a standardized radiolabeled scrambled-egg meal. After ingestion of 25 g xylitol, gastric emptying was markedly prolonged (T-1/2 58 +/- 5 min control vs 91 +/- 7 min after xylitol [p less than 0.01]). Since delayed gastric emptying may affect food intake, we evaluated the effects of xylitol on calorie intake. Food intake after oral preloading with water resulted in intake of 920 +/- 60 kcal vs 690 +/- 45 kcal after 25 g of xylitol. In contrast, a preload of glucose, fructose, or sucrose failed to suppress food intake. Although xylitol decreased food intake and also delayed gastric emptying, these effects may be unrelated. Our data suggest a role for xylitol as a potentially important agent in dietary control.     

Increasing preload volume with water reduces rated appetite but not food intake in healthy men even with minimum delay between preload and test meal

The role of gastric volume in the short-term control of eating in humans remains unclear, with some studies reporting that food volume alone can reduce appetite but others finding no such effect. A recent study in our laboratory, found effects of preload volume on subjective appetite (hunger, fullness) but not intake, and found effects of preload energy on intake but not appetite. That study used an interval of 30 min between serving preloads and the test meal, and the present study attempted to maximise the effects of the volume manipulation by removing the delay between the preload and test meal. We administered four soup-based preloads varying in volume (150 and 450 ml) using water, and energy density (1.4 and 4.2 kJ/ml) using maltodextrin, producing three energy levels (209, 629, 629 and 1886 kJ; repeated measures). These were followed immediately by an unlimited hot pasta lunch, during which food weight was monitored continuously by computer. Increasing soup volume at constant energy (629 kJ) reduced appetite ratings, but not intake. In contrast, increasing soup energy at constant volume (450 ml) reduced intake, without affecting appetite. The discrepancies between our results and other reported studies suggest that volume is more influential when intakes are large, or that there may be a threshold concentration for nutrients in the GI tract before volume alone is tangibly expressed in subsequent eating.     

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.     

Reproducibility of energy intake, gastric emptying, blood glucose, plasma insulin and cholecystokinin responses in healthy young males

Gastric emptying, as well as intragastric meal distribution, and gastrointestinal hormones, including cholecystokinin (CCK), play an important role in appetite regulation. The evaluation of gastrointestinal factors regulating food intake is commonly performed in healthy, lean, young male participants. It has, however, been suggested that there is a marked interindividual variability in the effects of nutrient 'preloads' on energy intake in this group. Whether there is significant intraindividual variation in acute energy intake after a nutrient preload, and, if so, how this relates to day-to-day differences in gastric emptying and gastrointestinal hormone release, is unclear. The purpose of the present paper is to evaluate the hypothesis that energy intake after a nutrient preload would be reproducible and associated with reproducible patterns of gastric emptying, intragastric distribution and gastrointestinal hormone release. Fifteen healthy men (age 25 (sem 5) years) consumed a glucose preload (50 g glucose in 300 ml water; 815 kJ) on three occasions. Gastric emptying and intragastric meal distribution (using three-dimensional ultrasound), blood glucose, plasma insulin and CCK concentrations and appetite perceptions were evaluated over 90 min, and energy intake from a cold buffet-style meal was then quantified. Energy intake was highly reproducible within individuals between visits (intraclass correlation coefficient, ri = 0.9). Gastric emptying, intragastric meal distribution, blood glucose, plasma insulin and CCK concentrations and appetite perceptions did not differ between visits (ri>0.7 for all). In healthy males, energy intake is highly reproducible, at least in the short term, and is associated with reproducible patterns of gastric emptying, glycaemia, insulinaemia and CCK release.     

Frequent feeding delays the gastric emptying of a subsequent meal

To assess the suitability of the 13C-octanoic acid breath test for measuring gastric emptying in circumstances other than the post-absorptive state, a preliminary study was performed where 6 hourly spaced isoenergetic meals preceded the determination of gastric emptying of a subsequent 2 MJ meal. Emptying was measured in three individuals on four separate occasions, with a reproducibility of 8%. A crossover study was then conducted to test the hypothesis that meal frequency can modulate the gastric emptying of a subsequent meal, with the potential to influence appetite regulation. Sixteen subjects were fed to energy balance, receiving food either as 2 isoenergetic meals 3 h apart or 6 isoenergetic meals fed hourly. Gastric emptying of a subsequent 2 MJ meal was investigated. Visual analogue scales were used throughout to assess appetite. The maximum rate of gastric emptying was unchanged but the onset of emptying was delayed by the more frequent feeding pattern. There was no significant difference in subjective appetite before or after the test meal. In conclusion, short-term increases in feeding frequency delayed the gastric emptying of a subsequent meal, but significant effects on post-meal appetite could not be demonstrated.     

Increasing Preload Volume with Water Reduces Rated Appetite But Not Food Intake in Healthy Men Even with Minimum Delay Between Preload and Test Meal

Abstract

The role of gastric volume in the short-term control of eating in humans remains unclear, with some studies reporting that food volume alone can reduce appetite but others finding no such effect. A recent study in our laboratory, found effects of preload volume on subjective appetite (hunger, fullness) but not intake, and found effects of preload energy on intake but not appetite. That study used an interval of 30 min between serving preloads and the test meal, and the present study attempted to maximise the effects of the volume manipulation by removing the delay between the preload and test meal. We administered four soup-based preloads varying in volume (150 and 450 ml) using water, and energy density (1.4 and 4.2 kJ/ml) using maltodextrin, producing three energy levels (209, 629, 629 and 1886 kJ; repeated measures). These were followed immediately by an unlimited hot pasta lunch, during which food weight was monitored continuously by computer. Increasing soup volume at constant energy (629 kJ) reduced appetite ratings, but not intake. In contrast, increasing soup energy at constant volume (450 ml) reduced intake, without affecting appetite. The discrepancies between our results and other reported studies suggest that volume is more influential when intakes are large, or that there may be a threshold concentration for nutrients in the GI tract before volume alone is tangibly expressed in subsequent eating.     

Gastric acid secretion, gastrin release, and gastric emptying in humans as affected by liquid meal temperature

We investigated the effect of the temperature of a liquid meal on intragastric temperature, gastric acid secretion, gastrin release, and gastric emptying in normal human subjects. Coffee (360 mL) was infused into the stomach through a nasogastric tube at 58 (steaming hot), 37, or 4 degrees C (ice cold). Intragastric temperature, measured by an intragastric temperature sensor attached to the nasogastric tube, returned to body temperature 16.7 +/- 2.7 min after the hot meal and 23.8 +/- 1.1 min after the cold meal. Gastric acid secretion increased after hot, warm, and cold coffee but the initial temperature of the meal had no effect on gastric acid secretion. The temperature of the meal also had no effect on serum gastrin concentrations, which increased significantly after all the meals. Gastric emptying of hot, warm, or cold coffee meals was similar. These findings indicate that over a wide temperature range, the temperature of a liquid meal has little effect on gastric function in humans.     

Soup preloads in a variety of forms reduce meal energy intake

Consuming soup can enhance satiety and reduce energy intake. Little is known about the influence on energy intake and satiety of varying the form of soup by altering the blending of ingredients. We tested the effects on meal intake of consuming different forms of soup as a preload: broth and vegetables served separately, chunky vegetable soup, chunky-pureed vegetable soup, or pureed vegetable soup. Normal-weight men and women (n = 60) came to the laboratory for lunch once a week for 5 weeks. Each week, one of four compulsory preloads, or no preload, was consumed prior to lunch. A test meal was consumed ad libitum 15 min after the soup was served. Results showed that consuming soup significantly reduced test meal intake and total meal energy intake (preload + test meal) compared to having no soup. When soup was consumed, subjects reduced meal energy intake by 20% (134+/-25 kcal; 561+/-105 kJ). The type of soup had no significant effect on test meal intake or total meal energy intake. Consuming a preload of low-energy-dense soup, in a variety of forms, is one strategy for moderating energy intake in adults.     

The effect of dietary fibre isolates on gastric secretion, acidity and emptying

1. In six volunteers, the effect of intragastric administration of different water-soluble chemical isolates of dietary fibre on gastric secretion, acidity and emptying was studied. 2. At 30 min after administration of the test meals, the stomach contents were completely aspirated and the volume, pH, phenol red concentration, total titratable acidity and different electrolytes were measured. 3. Compared with the control meal, the pH and unionized (combined) hydrogen concentrations were significantly higher (P less than 0.05) following most of the fibre-containing meals, while the total titratable acid concentration was not significantly different. None of the fibre-containing meals appreciably altered the volume or type of gastric secretion but had a low-grade variable effect on gastric emptying. 4. It is concluded that most dietary fibre isolates, although having a definite and notable buffering effect on the acid in the stomach, have a minimal effect on gastric secretion and a variable and small effect on gastric emptying.     

Preventing gastric sieving by blending a solid/water meal enhances satiation in healthy humans

Separation of solids and liquids within the stomach allows faster gastric emptying of liquids compared with solids, a phenomenon known as sieving. We tested the hypothesis that blending a solid and water meal would abolish sieving, preventing the early rapid decrease in gastric volume and thereby enhancing satiety. We carried out 2 separate studies. Study 1 was a 2-way, crossover, satiety study of 22 healthy volunteers who consumed roasted chicken and vegetables with a glass of water (1008 kJ) or the same blended to a soup. They completed satiety visual analogue scales at intervals for 3 h. Study 2 was a 2-way, crossover, mechanistic study of 18 volunteers who consumed the same meals and underwent an MRI to assess gastric emptying, gallbladder contraction, and small bowel water content (SBWC) at intervals for 3 h. In Study 1, the soup meal was associated with reduced hunger (P = 0.02). In Study 2, the volume of the gastric contents after the soup meal decreased more slowly than after the solid/liquid meal (P = 0.0003). The soup meal caused greater gallbladder contraction (P < 0.04). SBWC showed a biphasic response with an initial "gastric" phase during which SBWC was greater when the solid/liquid meal was consumed (P < 0.001) and a later "small bowel" phase when SBWC was greater when the soup meal was consumed (P < 0.01). Blending the solid/liquid meal to a soup delayed gastric emptying and increased the hormonal response to feeding, which may contribute to enhanced postprandial satiety.     

Effect of time of consumption of preloads on measures of satiety in healthy normal weight women

Differences in the time interval between preload and test meal may account for the variation in the satiating effects of whey protein found in previous preload studies. The objective was to compare the satiating effects (ad libitum meal intake at a set time after ingestion of preload) of whey protein (including glycomacropeptide) and maltodextrin carbohydrate and to determine whether such effects were influenced by the timing of preloads. On nine separate days, 19 healthy normal weight women consumed mixed composition preloads containing either water, or maltodextrin, or whey protein, 30, 60 or 120min before an ad libitum test meal. Whey protein reduced food intake (p<0.05) at the test meal more than maltodextrin and water (respective food energy intakes were 2343, 2584 and 3135kJ). The time interval between preload and test meal did not affect the food intake response. Total energy intake (preload+test meal) differed, with intake for the maltodextrin-enriched preload being greater than that for the whey protein-enriched preload, which was greater than for the water control. Total respective energy intakes were 3955, 3676 and 3135kJ. Subjective ratings of appetite did not support a greater satiating effect of whey protein versus maltodextrin on food intake but there was evidence for a satiating effect of maltodextrin and whey protein versus the water control.     

Casein and whey exert different effects on plasma amino acid profiles,gastrointestinal hormone secretion and appetite

Protein, generally agreed to be the most satiating macronutrient, may differ in its effects on appetite depending on the protein source and variation in digestion and absorption. We investigated the effects of two milk protein types, casein and whey, on food intake and subjective ratings of hunger and fullness, and on postprandial metabolite and gastrointestinal hormone responses. Two studies were undertaken. The first study showed that energy intake from a buffet meal ad libitum was significantly less 90 min after a 1700 kJ liquid preload containing 48 g whey, compared with an equivalent casein preload (P<0.05). In the second study, the same whey preload led to a 28 % increase in postprandial plasma amino acid concentrations over 3 h compared with casein (incremental area under the curve (iAUC), P<0.05). Plasma cholecystokinin (CCK) was increased by 60 % (iAUC, P<0.005), glucagon-like peptide (GLP)-1 by 65 % (iAUC, P<0.05) and glucose-dependent insulinotropic polypeptide by 36 % (iAUC, P<0.01) following the whey preload compared with the casein. Gastric emptying was influenced by protein type as evidenced by differing plasma paracetamol profiles with the two preloads. Greater subjective satiety followed the whey test meal (P<0.05). These results implicate post-absorptive increases in plasma amino acids together with both CCK and GLP-1 as potential mediators of the increased satiety response to whey and emphasise the importance of considering the impact of protein type on the appetite response to a mixed meal.     

Acute tryptophan depletion slows gastric emptying in females

Serotonin (5-HT) is an important neurotransmitter involved in the brain-gut axis. It is possible to lower the 5-HT level in the body by means of a nutritional intervention using an amino acid mixture; the acute tryptophan depletion (ATD) method. We studied the effect of ATD on gastric emptying in healthy females, who received both ATD and placebo in a random order. Gastric emptying was measured using the [(13)C]octanoic acid breath test. The present data demonstrate significant differences in both gastric emptying and lag phase (Tlag) between the ATD and placebo experiment. Eight out of ten subjects showed a delayed gastric emptying in the ATD experiment. Both the gastric half-emptying time (T1/2) and the Tlag were significantly higher in the ATD experiment. T1/2 in the ATD experiment was 137.2 (range 76.2-634.8) min; T1/2 for the placebo experiment was 98.5 (range 63.7-168.8) min (P=0.028). Tlag in the ATD experiment was 83.7 (range 45.1-356.2) min; Tlag for the placebo experiment was 56.9 (range 23.2-101.2) min (P=0.007). We conclude that lowering the 5-HT level in the body using the ATD method leads to a significantly delayed gastric emptying of a solid meal. Nutritional manipulation of the serotonergic system in healthy volunteers may lead to alterations in gastrointestinal motility.     

Failure to Reduce Short-term Appetite Following Alcohol is Independent of Beliefs about the Presence of Alcohol

Previously, it has been reported that energy consumed as alcohol prior to lunch does not result in subsequent reductions in voluntary food intake, and in some situations alcohol can increase subsequent appetite. The present study extends these findings by examining the effects of beliefs about alcohol content. Eighteen unrestrained men ate lunch 20 min after a preload of either water, an alcoholic beer or a non-alcoholic beer matched for energy content. Food intake was significantly less following the non-alcoholic beer than after alcohol or water, but when preload energy was included subjects had a higher overall energy intake on the day they consumed alcohol compared with both water and no-alcohol conditions. There were no significant differences in hunger or fullness ratings following the three drinks before or after the test meal, but the specific relationship between rated hunger and intake within the test meal was altered by the drink manipulation. The rate at which hunger decreased, and fullness increased, was slower after alcohol than after water or no-alcohol. The drinks did not alter the pleasantness of the test meal or increase hunger at the start of eating. When contrasted with previous work, these data confirm that alcohol consumed before lunch fails to reduce subsequent food intake, but also suggests that changes in rated appetite are influenced by beliefs about alcohol content.     

Failure to reduce short-term appetite following alcohol is independent of beliefs about the presence of alcohol

Previously, it has been reported that energy consumed as alcohol prior to lunch does not result in subsequent reductions in voluntary food intake, and in some situations alcohol can increase subsequent appetite. The present study extends these findings by examining the effects of beliefs about alcohol content. Eighteen unrestrained men ate lunch 20 min after a preload of either water, an alcoholic beer or a non-alcoholic beer matched for energy content. Food intake was significantly less following the non-alcoholic beer than after alcohol or water, but when preload energy was included subjects had a higher overall energy intake on the day they consumed alcohol compared with both water and no-alcohol conditions. There were no significant differences in hunger or fullness ratings following the three drinks before or after the test meal, but the specific relationship between rated hunger and intake within the test meal was altered by the drink manipulation. The rate at which hunger decreased, and fullness increased, was slower after alcohol than after water or no-alcohol. The drinks did not alter the pleasantness of the test meal or increase hunger at the start of eating. When contrasted with previous work, these data confirm that alcohol consumed before lunch fails to reduce subsequent food intake, but also suggests that changes in rated appetite are influenced by beliefs about alcohol content.     

Caffeine,coffee, and appetite control: a review

Coffee and caffeine consumption has global popularity. However, evidence for the potential of these dietary constituents to influence energy intake, gut physiology, and appetite perceptions remains unclear. The purpose of this review was to examine the evidence regarding coffee and caffeine’s influence on energy intake and appetite control. The literature was examined for studies that assessed the effects of caffeine and coffee on energy intake, gastric emptying, appetite-related hormones, and perceptual measures of appetite. The literature review indicated that coffee administered 3–4.5?h before a meal had minimal influence on food and macronutrient intake, while caffeine ingested 0.5–4?h before a meal may suppress acute energy intake. Evidence regarding the influence of caffeine and coffee on gastric emptying, appetite hormones, and appetite perceptions was equivocal. The influence of covariates such as genetics of caffeine metabolism and bitter taste phenotype remain unknown; longer controlled studies are needed.     

Preload of slowly digestible carbohydrate microspheres decreases gastric emptying rate of subsequent meal in humans

Gastric emptying rate influences how fast the nutrients of a meal are delivered to the body, and when slow, it moderates glycemic response and may impact satiety. Carbohydrates are one of the macronutrients that trigger the ileal brake, and we hypothesized that slowly digestible carbohydrate (SDC) administered in a premeal load would delay gastric emptying. A crossover design study was conducted with 10 healthy adults using fabricated SDC-microspheres (cooked) that were given 20 minutes before a non-nutritive viscous paste meal. There were 4 treatment arms, each separated by a 1-week washout period, consisting of (1) the paste alone, (2) a rapidly digesting maltodextrin (Polycose) preload followed by the paste 20 minutes later, (3) an SDC-microsphere preload followed by the paste, and (4) a comparably slower SDC-microsphere preload followed by the paste. A ¹³C-labeled octanoic acid breath test method was used to measure gastric emptying, with the label incorporated into the non-nutritive paste. The microspheres were less than 1 mm in diameter (a size that does not require breakdown in the stomach before emptying) and, after cooking, were of the same density value. Compared with the paste alone, both of the SDC-microsphere preloads (slow and comparably slower digesting) decreased gastric emptying rate of the paste, with the latter having the most effect (half-emptying times of 1.7, 2.3, and 2.8 hours, respectively [each different at P < .05]). In conclusion, SDCs decreased gastric emptying rate, and this was suggested to be due to a triggering of the ileal brake.     

Comparison of gastric emptying of a solid and a liquid nutritional rehabilitation food

OBJECTIVE: To compare gastric emptying of a solid and a liquid nutritional rehabilitation food. DESIGN: Cross-over trial. Eight volunteers took, in random order at least 1 week apart, 2100 kJ of a solid and a liquid nutritional rehabilitation food with added labelled [13C] glycine. SETTING: Research ward for healthy volunteers. SUBJECTS: Eight healthy volunteers. METHODS: Appearance of 13CO2 was monitored in expired gas every 15 min for 240 min after meal intake and compared between solid and liquid meals. Parameters of gastric emptying were then calculated. RESULTS: Gastric half-emptying time was slightly longer for solid meal compared to liquid meal (101+/-6.0 vs 88+/-9.8 min, P=0.24). 13CO2 excretion peaked 138+/-5.3 min after the solid meal compared with 119+/-8.6 min with liquid meal (P=0.06). 13CO2 excretion was higher for the liquid food up to 110 min after the meal but then became higher for the solid food. Analysis of variance for repeated measures of 13CO2 excretion showed a significant interaction term between the type of food and time indicating a delayed elimination of 13CO2 for the solid food (P=0.018). CONCLUSIONS: Attempts to replace liquid nutritional rehabilitation foods by a solid food in malnourished patients should take into account a possible slower gastric emptying. SPONSORSHIP: Supported by a grant from Nutriset (Malaunay, France) and ANVAR (Agence Nationale de la Valorisation de la Recherche, contract no. A9703021P).     

The effect of incorporating fat into different components of a meal on gastric emptying and postprandial blood glucose and insulin responses

1. Three studies were carried out in each of six normal volunteers to investigate how lipid, when given at different stages during the course of a meal, affects gastric emptying and postprandial blood glucose and insulin concentrations. 2. The control meal consisted of 300 ml beef consommé (50 kJ, 12 kcal), followed 20 min later by 300 g mashed potato (908 kJ, 217 kcal). In the two test meals, 60 g margarine were incorporated into either the soup or the mashed potato. 3. The addition of margarine to either component of the meal delayed gastric emptying of the mashed potato (P less than 0.05), but the pattern varied according to the component to which the fat was added. 4. Incorporation of fat into the soup increased the lag phase (P less than 0.05) but did not influence the slope of emptying of the mashed potato, while incorporation of fat into the mashed potato reduced the slope of emptying of the mashed potato (P less than 0.05) but did not influence the lag phase. 5. Addition of fat to either component of the meal reduced postprandial blood glucose (P less than 0.05) and insulin responses, but when the fat was incorporated in the soup, peak glucose and insulin responses were delayed as well (P less than 0.05). 6. The results show that the effect of fat on gastric emptying and absorption of nutrients depends on when, in relation to the other components of the meal, the fat is consumed.     

Xylitol vs glucose: effect on the rate of gastric emptying and motilin, insulin, and gastric inhibitory polypeptide release

The effect of xylitol and glucose on the rate of gastric emptying and intestinal transit and on motilin, gastric inhibitory polypeptide (GIP), and insulin release were studied in human volunteers. A single oral dose of 200 mL water containing 30 g glucose or 30 g xylitol, mixed with a 99mtechnetium-tin (99mTc-Sn) colloid, was used. Similar dosing without the label was used in motilin, GIP, and insulin studies. Xylitol decreased the rate of gastric emptying but concomitantly accelerated intestinal transit compared with glucose. The half-times for gastric emptying were 77.5 +/- 4.6 and 39.8 +/- 3.4 min after ingestion of xylitol and glucose solutions, respectively. Glucose suppressed motilin and stimulated GIP secretion; xylitol stimulated motilin secretion but had no effect on GIP, which is currently the main candidate for the role of enterogastrone. The accelerated intestinal transit and increase in plasma motilin observed after xylitol ingestion were thought to be causally related to the diarrhea and gastrointestinal discomfort produced by it.