MJ Meal Research Articles

Impact of pre‐exercise rapid‐acting insulin reductions on ketogenesis following running in Type 1 diabetes

This study examined the effects of reductions to pre-exercise rapid-acting insulin dose on changes in blood beta-hydroxybutyrate, glucose, acid-base balance and counter-regulatory hormone responses to prolonged running in individuals with Type 1 diabetes. Following ethical approval, seven participants with Type 1 diabetes (34±2 years, BMI 27±1 kg/m(2) ) completed this study. After preliminary testing, participants attended the laboratory four times, each time consuming a 1.12 MJ meal (60 g carbohydrate, 2 g fat, 2 g protein), with randomized amounts of their rapid-acting insulin: Full dose (mean 7.3±0.2 units), 75% dose (mean 5.4±0.1 units), 50% dose (mean 3.7±0.1 units) or 25% dose (mean 1.8±0.1 units). After 2-h rest, participants completed 45 min running at 70±1% peak rate of oxygen consumption (VO(2peak) ). Blood metabolites and hormones were recorded over the 2-h rest and 3-h recovery. Data were analysed using repeated-measures ANOVA. Serum insulin peaked at 60 min in all conditions and was lowest after 25% insulin dose compared with full dose (P=0.03). After the 25% insulin dose immediately pre-exercise glucose concentration was higher than after the full or 50% dose (P<0.05). Resting beta-hydroxybutyrate gradually decreased during 2-h rest (P<0.05) with a similar post-exercise peak of beta-hydroxybutyrate at 3 h (P>0.05). Post-exercise blood pH increased for 5 min to a similar extent with all insulin doses , but the rise with the 25% dose was less compared with the full dose (P=0.01). Blood lactate and plasma catecholamines increased after running similarly with all insulin reduction conditions (P<0.05). Blood glucose area under the curve (BG(auc) ) after the 25% insulin dose was greater than after the 75% dose (P=0.02). Ketogenesis following running was not influenced by reductions in pre-exercise rapid-acting insulin dose. This important preparatory strategy aids preservation of blood glucose but poses no greater risk to exercise-induced ketone body formation.

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.

Relationship between acceleration of gastric emptying and oesophageal acid exposure in patients with endoscopy-negative gastro-oesophageal reflux disease

Objective. A delay in gastric emptying has been reported in patients with gastro-oesophageal reflux disease (GORD), but its role in increasing the number of reflux episodes is still debated. The aim of this study was to assess the relationship between acceleration of gastric emptying and gastro-oesophageal reflux in patients with endoscopy-negative GORD and pathological oesophageal acid exposure. Material and methods. Twelve patients (7 M, age range 24–65 years) underwent 6-h postprandial (2.1 MJ meal) combined gastric emptying by real-time ultrasonography and intra-oesophageal pH monitoring after cisapride (20 mg b.i.d.) and placebo for 3 days, on two separate occasions at least 7 days apart in double-blind randomized order. Gastric emptying after placebo was also measured in 12 healthy volunteers (7 M, age range 25–54 years). Results. In the patients’ group, the area under the emptying time curve was greater (p<0.01), and half and total emptying times prolonged (p<0.01) compared to the healthy subjects, 115 min (mean)±6 (SEM) versus 86±6 and 232 min±16 versus 160±7, respectively. Cisapride accelerated both half- and total gastric emptying (p<0.02): −22 min (mean); −10 to −34 (95% CI) and −48 min; −10 to −85, respectively, decreased both percentage of time at pH < 4 (p<0.01) and number of reflux episodes (p<0.05). However, no relationship was found between changes in gastric emptying and in the reflux variables by linear regression analysis (R2<0.005). Conclusion. The emptying rate of the whole stomach is not a major determinant of gastro-oesophageal reflux.

Areca nut, energy metabolism and hunger in Asian men

Background : The nut of the Areca catechu palm has long been attributed effects on hunger and the digestive process. Objectives : The objectives were to assess experimentally effects of areca nut on fasting and postprandial energy metabolism, substrate utilization and hunger. Subjects and methods : Two randomized, placebo-controlled, double-blind studies were undertaken. In study 1, eight Indian men received bioadhesive gels delivering 0, 5, 10 or 20 mg arecoline to the buccal sulcus after an overnight fast. Resting energy expenditure and substrate utilization were determined by ventilated hood calorimetry over 6 h during which hunger was rated on five occasions. In study 2, 15 Indian men received gels delivering 0 or 10 mg arecoline after consuming a 2.5 MJ meal, and the same protocol was then applied as in study 1. Results : Fasting resting energy expenditures exceeded basal metabolic rate (BMR) by 5.4 - 0.8% (Mean - SE) after placebo, and 5.1 - 0.7% after 20 mg arecoline, but by 0.9 - 0.8% and 0.7 - 0.5% following 5 mg and 10 mg arecoline, respectively. Carbohydrate (CHO) utilization rates rose after areca nut compared to placebo (F 3,252 = 7.3, p < 0.001). Hunger varied across doses ( h 2 = 10.5, p < 0.02), being lowest after 10 mg and highest after 20 mg, and was influenced by interaction of dose with delta resting energy expenditure. In study 2, areca dose interacted with fat-free mass (FFM) to lower by 5.4 - 11.2% the thermic effect of a meal (F 1,28 = 4.9, p = 0.05), and retarded peak 'digestive-phase' thermogenesis by 60 min (F 1,58 = 5.7, p = 0.02). Postprandial delta CHO utilization was greater (F 1,28 = 4.5, p = 0.05), and hunger was lower ( h : 2 = 3.8, p = 0.05), after areca nut. The areca nut altered relationships of hunger to thermic effects of the meal, and to delta substrate utilization, in ways consistent with appetite suppression. Conclusion : Areca nut constituents modulate metabolic signals regulating appetite in man. This concurs with customary belief.

Effect of Calories and Fat on Postprandial Gastro-oesophageal Reflux

Background: Gastro-oesophageal reflux (GOR) is commonly considered to be worsened by fatty food, but it has recently been shown that changing the fat content of equicaloric meals has no effect on GOR over a 3-h postprandial period. Our aims were to verify this finding over a longer postprandial period and test the hypothesis that increasing the caloric content of balanced meals increases GOR. Methods: Thirteen healthy subjects (6 men) aged 19-31 years underwent 6-h oesophageal pH monitoring after 3 solid/liquid meals of the same volume and osmolarity eaten on separate days in a randomized order: a) high fat (58% fat) 2.8 MJ; b) balanced (23% fat) 2.8 MJ; and c) balanced low calorie (25% fat) 1.6 MJ. Results: The mean percentage of time at pH < 4 and the mean number of reflux episodes after the balanced 2.8 MJ meal (3.0% and 11.5, respectively) were higher ( P < 0.05) than after the balanced 1.6 MJ meal (1.6% and 7.2) and similar to those after the equicaloric (2.8 MJ) high-fat meal (2.5% and 9.3). Acid clearance time was similar after all three meals. Conclusions: Our data suggest that advice on dietary habits in patients with GOR disease should be concentrated on decreasing the caloric load of meals rather than their fat content.

Small bowel transit of a bran meal residue in humans: sieving of solids from liquids and response to feeding

Background—Ileal motor patterns are adapted to the propulsion of viscous meal residue, such as bran, which accumulates in the distal ileum postprandially.Aims—To examine the effects of a second liquid/solid meal...

The effect of meal size on the cardiovascular responses to food ingestion

Cardiac output (CO; indirect Fick), blood pressure (BP) and heart rate (HR; oscillometry), superior mesenteric artery blood flow (SMABF; Duplex Doppler) and calf blood flow (CBF; venous occlusion plethysmography) were recorded in the fasted state and for 120 min following the ingestion of 1, 2, and 3 MJ, high-carbohydrate meals in eight healthy females. BP was unchanged following food. HR (P < 0.0005) and CO (P < 0.005) rose significantly following all three meals. Integrated increments in CO over the postprandial period were greater after 3 MJ compared with the 1 and 2 MJ meals (P < 0.05). SMABF rose significantly following all three meals. The pattern of blood flow response was significantly different between the 1 and 3 MJ meals (interaction effect P < 0.02, ANOVA), with blood flow after the 3 MJ meal being significantly greater than flow after the 1 MJ meal at 15, 60, and 90 min. Similarly, the pattern of response was significantly different after the 2 and 3 MJ meals (interaction effect P < 0.03, ANOVA), with blood flow being significantly greater at 15 and 90 min after the 3 MJ meal. CBF fell significantly in the first 15 min after the 3 MJ meal and then recovered towards baseline values. No other significant changes in CBF were recorded. There are substantial peripheral and central cardiovascular changes after food in man and there appears to be a relationship between meal size and the extent of these changes.

Superior mesenteric artery blood flow and gastric emptying in humans and the differential effects of high fat and high carbohydrate meals.

This study was designed to determine if the differential effect of high fat and high carbohydrate meals on mesenteric blood flow is a result of changed gastric emptying rate. Eight healthy men were studied twice. Superior mesenteric artery blood flow (Doppler ultrasound) was measured before and after a 2.5 MJ meal (either 74% of the energy as carbohydrate or 71% as fat). Emptying of meals was followed by gamma-scintigraphy. The pattern of the superior mesenteric artery blood flow response was different after the two meals (interaction effect p < 0.001 analysis of variance), with a far more sustained response after fat. The time by which half the meal had emptied (t50) was also significantly greater after fat (p < 0.02). Superior mesenteric artery blood flow corresponding to t50 was 449 ml/min after carbohydrate and 592 ml/min after fat. There was a significant curvilinear relation between the superior mesenteric artery blood flow response and gastric emptying after carbohydrate (r2 = 0.94) and no relation at all after fat. This study confirms the finding that ingestion of meals with a high fat content slows gastric emptying compared with meals with a high carbohydrate content in healthy volunteers. A more sustained mesenteric hyperaemia was also recorded after the fat meal compared with the carbohydrate meal. The relation, however, between the volume of meal remaining in the stomach and the mesenteric response was considerably different after the two meals. Further study is required to elucidate the mechanism behind the vascular responses recorded in the mesenteric bed after food in humans.

The Effect of Caffeine on Postprandial Hypotension in the Elderly

In a double-blind, randomized trial the effects of caffeinated and decaffeinated drinks on postprandial hemodynamic and neurohumoral changes were studied in seven fit, elderly subjects after a standard 2.4MJ meal. There was a significant difference in supine postprandial systolic blood pressure between the placebo and caffeine phases (P less than 0.01); at 60 minutes, supine systolic blood pressure had fallen 14 mmHg [95% confidence interval (CI)-7 to-21 mmHg, p less than 0.01) after placebo, but was unchanged after caffeine (+9 mmHg, CI 0 to 18 mmHg, NS]. Similar differences between placebo and caffeine were seen in erect systolic and diastolic blood pressure (P less than 0.01), although orthostatic tolerance was maintained throughout each study period. Postprandial plasma noradrenaline levels were higher (P less than 0.02) and the increase greater (P less than 0.02) after caffeine than after placebo. Caffeine administered at the end of a standard test meal prevents the postprandial fall in blood pressure in fit, elderly subjects. The clinical relevance of this finding has yet to be determined, but it may offer a simple remedy for patients with symptomatic postprandial hypotension.

The effect of environmental temperature on prandial changes in leucocyte sodium transport in man.

Cellular sodium transport via the Na+, K+-ATPase contributes significantly to daily energy expenditure. The effect of a meal on leucocyte Na+ transport and intracellular electrolytes was therefore investigated in lean normal subjects at room temperatures of 23 degrees and 33 degrees, to determine if the Na pump responds to the need for thermogenesis. In the fasting state, the ouabain-sensitive efflux rate which reflects active Na+ transport, and the intracellular electrolytes were similar. At 2 h after eating a 4.2 MJ (1000 kcal) meal, the ouabain-sensitive efflux rate constant rose when the room temperature was 23 degrees but not at 33 degrees. The ouabain-sensitive Na+ efflux rate, an index of active Na+ transport, rose post-prandially at 23 degrees only. The post-prandial activation of leucocyte active Na efflux in normal subjects was blunted at higher environmental temperatures, when the need for thermogenesis was reduced.

Leucocyte sodium pump activity after meals or insulin in normal and obese subjects: cause for increased energetic efficiency in obesity?

As cellular sodium pumping is an energy consuming process and differences in the obese may account for their energetic efficiency, leucocyte sodium-22 efflux was studied in obese and normal volunteers both in the fasting state and after a test meal or infusion of glucose and insulin intravenously. The 22Na ouabain sensitive efflux rate constant was significantly higher in obese subjects than normal (mean (1 SD) 2.69 (0.40)/h v 2.35 (0.49)/h). Two hours after a 4.2 MJ (1000 kcal) meal there was an increase in the efflux rate constant from its fasting value in normal weight subjects (2.39 (0.33)/h to 2.71 (0.40)/h) but not in obese subjects (2.65 (0.54)/h to 2.61 (0.58)/h). The rise in ouabain sensitive efflux rates was significantly higher in normal than obese subjects. Both groups showed a rise in intracellular sodium concentrations. The euglycaemic clamp produced similar results. Feeding or infusion of insulin increases sodium pump activity more in normal than obese subjects. This difference may contribute to any defective dietary thermogenesis in obesity, which may lead to energetic efficiency and a tendency to gain weight.

Genotype dependency of the thermic effect of a meal and associated hormonal changes following short-term overfeeding

The purpose of this experiment was to assess the effects of short-term overfeeding (mixed diet) on the thermic effect of a meal (TEM) and associated hormonal changes and to investigate the role of the genotype in the observed changes. Six pairs of male sedentary monozygotic (MZ) twins consumed an extra 1,000 kcal per day over their individual level of energy expenditure while maintaining a sedentary existence. Resting metabolic rate (RMR) and TEM following a 4.2 MJ meal challenge was measured before and after 22 days of overfeeding. RMR did not change significantly (7% elevation) in response to the positive caloric stimulus, whereas significant increases ( P < 0.01) in TEM were observed. Moreover, postprandial insulin and glucose responses were not modified. Overfeeding did not significantly alter catecholamine levels but induced significant elevations in plasma levels of T3 and T4 ( P < 0.05). Changes in RMR exhibited moderate but nonsignificant within twin pair resemblance in response whereas significant within pair resemblance was noted in the magnitude of TEM changes induced by overfeeding ( P < 0.05). Hormonal responses exhibited a weaker genotype dependency. These results suggest that short-term overfeeding can induce an elevation in TEM with accompanying increases in T3 and T4. Large individual response variation in metabolic and hormonal measures were observed. The similarity of response within twin pairs suggests that sensitivity to change in TEM induced by short-term overfeeding is genetically influenced.