Differential effect of protein and fat ingestion on blood glucose responses to high- and low-glycemic-index carbohydrates in noninsulin-dependent diabetic subjects

Six noninsulin-dependent diabetic subjects received meals containing 25 g carbohydrate either as potato or as spaghetti. The meals were repeated with the addition of 25 g protein and with 25 g protein and 25 g fat. Blood glucose and insulin responses were measured for 4 h after the test meal. When carbohydrate was given alone, the blood glucose and serum insulin increments were higher for the potato meal. The addition of protein increased the insulin responses to both carbohydrates and slightly reduced the glycemic response to mashed potato (F = 2.04, p less than 0.05). The further addition of fat reduced the glycemic response to mashed potato (F = 14.63, p less than 0.001) without any change in the blood glucose response to spaghetti (F = 0.94, NS). The different responses to coingestion of protein and fat reduced the difference between the glycemic responses to the two carbohydrates.     

The effects of fiber enrichment of pasta and fat content on gastric emptying,GLP-1, glucose,and insulin responses to a meal

OBJECTIVE: To assess whether the addition of viscous fiber at an amount recommended by the US FDA to allow a 'low saturated fat, cholesterol, soluble fiber and coronary heart disease', health claim label on a food package (1.7 g psyllium) and/or fat (30 g sunflower oil and 3 g sodium propionate) to a pasta meal would affect gastric emptying, postprandial glucose, insulin and GLP-1 concentrations. DESIGN: Ten subjects participated in a two-by-two single blind randomized crossover study. Four meals containing 50 g of available carbohydrate were consumed: pasta with or without psyllium enrichment served with a tomato sauce with (520 kcal per meal) and without (240 kcal per meal) fat. Blood samples were taken for 240 min following the meal and all subjects consumed a buffet meal at the end of the study. Gastric emptying was measured using the paracetamol absorption test. Blood was analysed for glucose, insulin, GLP-1. Visual analog scales were used to record feelings of hunger, pleasantness and nausea. RESULTS: The psyllium-enriched pasta had no significant effect on gastric emptying or the incremental area under the curve (IAUC) for GLP-1, insulin or glucose compared with the control pasta. The addition of polyunsaturated fat and sodium propionate significantly increased the IAUC for GLP-1 (P<0.001), delaying gastric emptying (P<0.002), and decreasing glucose (P<0.002). CONCLUSIONS: A dose of 1.7 g psyllium did not evoke measurable effects on gastric emptying, postprandial GLP-1, insulin or glucose metabolism. However the addition of 30 g of oil and 3 g of sodium propionate to the pasta did reduce gastric emptying, increase GLP-1 and reduce glucose and insulin concentrations. While this short-term study may have implications in terms of reducing the risk of diabetes and improving coronary risk factor profiles the long term effects of these nutrients need to be studied.     

Relationship between the rate of gastric emptying and glucose and insulin responses to starchy foods in young healthy adults

Twelve young healthy adults (five men, seven women) ingested four test meals on four occasions so we could examine the relationship between the rate of gastric emptying (GE) and the glucose response to different starchy foods. Each meal consisted of one food product containing 50 g starch: spaghetti, rice, French bread, or mashed potato. Basal and postprandial glucose and insulin responses were measured for 3 h. The foods were labeled with 3.7 MBq Tc99m-albumin and GE was studied by scintigraphy for 3 h. The rate of GE (expressed by the GE half-time) was fastest for mashed potatoes, then bread, rice, and slowest for spaghetti. Blood glucose and serum insulin responses were similar. A significant negative correlation was found between the GE half-time and the maximum variation in blood glucose level (r = -0.6, p less than 0.0001). The glucose response to all four foods is strongly related to the GE rate.     

Gastric emptying and glycemic response after ingestion of mashed bean or potato flakes in composite meals

Two meals of mashed-bean or potato flakes and meat were served in random order to six healthy male subjects to determine effects on gastric emptying and glycemic reactions. The meals had comparable physical appearance and contained similar amounts of digestible carbohydrate, fat, and protein. No difference in gastric emptying, recorded by gamma camera after mixing 51Cr with the meals, was found between the meals. The bean-flakes meal gave significantly lower blood glucose (p less than 0.01) and serum insulin (p less than 0.05) concentrations than did the potato-flakes meal. The overall blood glucose response, calculated as incremental area under the curves for 2 h, also differed between the meals (p less than 0.05) whereas the overall insulin response did not differ significantly. The low glycemic response after bean flakes could not be explained by the gastric emptying rate, which provides additional evidence for the slow digestion of bean starch in the small intestine.     

Dietary guar gum effects on postprandial blood glucose, insulin and hydroxyproline in humans

Meals (425 kcal) containing various doses of guar gum (0, 2.5, 7.5 or 12.5 g) were ingested by nine healthy male subjects after a 12-h fast. The rise in blood glucose was higher after the control meal without guar gum than after the guar gum-containing meals, which all gave a similar rise in glucose. In contrast, increased doses of guar gum led to a greater reduction in the postprandial rise in insulin. The postprandial increase in serum hydroxyproline, an amino acid added to all meals, was decreased in a similar manner by all of the guar gum doses. Gastric emptying was measured after the control meal without guar gum and the meal containing 12.5 g of guar gum by monitoring 51Cr, which was added to the meals. Guar gum was found to reduce the variation between individuals, as well as the initial rate of gastric emptying, which correlated with changes in both serum hydroxyproline (rs = 0.93, P less than 0.01) and blood glucose (rs = 0.83, P less than 0.01). The effectiveness of guar gum in reducing postprandial response was lost after heating and homogenization for canning. A threshold in the reduction in rise of glucose or hydroxyproline was reached with the lowest dose (2.5 g) of viscous guar gum; larger doses had no additional effects. The reduced absorption seems to be an effect of a slower gastric emptying rate.     

A small dose of soluble alginate-fiber affects postprandial glycemia and gastric emptying in humans with diabetes.

Seven men with well-controlled, noninsulin-dependent (type 2) diabetes ingested on two different mornings, in random order, meals with or without a 5.0-g sodium alginate supplement (algae-isolate, 75% soluble fiber). The meals contained similar amounts of digestible carbohydrates, fat and protein. The gastric emptying rate of the meal containing sodium alginate, measured by detection of 51Cr mixed into the meals, was significantly slower than that of the fiber-free meal. Sodium alginate also induced significantly lower postprandial rises in blood glucose, serum insulin and plasma C-peptide. The diminished glucose response after the addition of sodium alginate could be correlated to the delayed gastric emptying rate induced by the fiber (rs = 0.92, P less than 0.01).     

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.     

Almonds decrease postprandial glycemia, insulinemia, and oxidative damage in healthy individuals

Strategies that decrease postprandial glucose excursions, including digestive enzyme inhibition, and low glycemic index diets result in lower diabetes incidence and coronary heart disease (CHD) risk, possibly through lower postprandial oxidative damage to lipids and proteins. We therefore assessed the effect of decreasing postprandial glucose excursions on measures of oxidative damage. Fifteen healthy subjects ate 2 bread control meals and 3 test meals: almonds and bread; parboiled rice; and instant mashed potatoes, balanced in carbohydrate, fat, and protein, using butter and cheese. We obtained blood samples at baseline and for 4 h postprandially. Glycemic indices for the rice (38 +/- 6) and almond meals (55 +/- 7) were less than for the potato meal (94 +/- 11) (P < 0.003), as were the postprandial areas under the insulin concentration time curve (P < 0.001). No postmeal treatment differences were seen in total antioxidant capacity. However, the serum protein thiol concentration increased following the almond meal (15 +/- 14 mmol/L), indicating less oxidative protein damage, and decreased after the control bread, rice, and potato meals (-10 +/- 8 mmol/L), when data from these 3 meals were pooled (P = 0.021). The change in protein thiols was also negatively related to the postprandial incremental peak glucose (r = -0.29, n = 60 observations, P = 0.026) and peak insulin responses (r = -0.26, n = 60 observations, P = 0.046). Therefore, lowering postprandial glucose excursions may decrease the risk of oxidative damage to proteins. Almonds are likely to lower this risk by decreasing the glycemic excursion and by providing antioxidants. These actions may relate to mechanisms by which nuts are associated with a decreased risk of CHD.     

Title: Differentiating the effects of whey protein and guar gum preloads on postprandial glycemia in type 2 diabetes

Background and aimsWhey protein and guar gum have both been reported to reduce postprandial glycemia in health and type 2 diabetes, associated with stimulation of glucagon-like peptide-1 (GLP-1) and/or slowing of gastric emptying. Our aim was to evaluate, in type 2 diabetes, the acute effects of low dose “preloads” of whey and guar, given alone or in combination before a meal, on postprandial glycemia, insulin, GLP-1, and gastric emptying.Methods21 patients with type 2 diabetes, managed by diet or metformin alone, were each studied on 4 days. They received a preload “shake” 15min before a mashed potato meal (368.5 kcal) labeled with ¹³C-octanoic-acid. The preloads comprised either (i) 17 g whey (W), (ii) 5 g guar (G), (iii) 17 g whey + 5 g guar (WG) each sweetened with 60 mg sucralose, and (iv) 60 mg sucralose alone (control; C), all dissolved in 150 mL water. Venous blood was sampled frequently for measurements of glucose, insulin, and GLP-1 concentrations. Gastric half-emptying time (T50) was calculated from breath ¹³CO₂ excretion over 240 min.ResultsPostprandial blood glucose concentrations were lower with W and WG compared to C (each P < 0.0001, treatment × time interaction), and lower after G than C only at 30min. Insulin, GLP-1, and glucagon concentrations were higher after W than WG, G, or C (P < 0.05, treatment × time interaction), without differences between the latter three. Gastric emptying was slower with W (T50: 179.6 ± 6.1 min, P < 0.05) and WG (T50: 197.6 ± 9.7 min, P < 0.0001) when compared to C (T50: 162.9 ± 6.2 min), but did not differ between G (T50: 171.3 ± 7.0) and C (P > 0.99).ConclusionBoth whey and whey/guar preloads reduced postprandial glycemia, associated with slowing of gastric emptying. Low dose guar was less effective as a preload for glucose-lowering and did not slow gastric emptying.Clinical Trial Registry number and websiteAustralian and New Zealand Clinical Trials Registry, Trial ID ACTRN12615001272583, http://www.anzctr.org.au     

Protein and fat modify the glycaemic and insulinaemic responses to a mashed potato-based meal

Potatoes, especially mashed potatoes, are known to result in high glycaemic and insulinaemic responses. However, in most meals, potatoes are accompanied by other foods. The objective of the present study was to investigate how glycaemic and insulinaemic responses to a mashed potato meal changed when a high-fat food (rapeseed oil), a high-protein food (chicken breast) and/or salad were added to the meal. Healthy subjects (n 11) ingested the test meals once and the reference food (glucose solution) twice in a random order at 1-week intervals. Capillary blood samples were then drawn for 2 h, and glucose and insulin were analysed. The 2 h glycaemic responses to six mashed potato-containing meals varied more than twofold. The glycaemic index (GI) of pure mashed potato was 108, whereas combined with chicken breast, rapeseed oil and salad, it was only 54. The latter GI also differed considerably from its predicted value of 103, which was based on the individual GI of the components of the meal. The insulinaemic indices of the mashed potato-based meals varied between 94 and 148. Chicken breast in the meal increased the insulinaemic response, and rapeseed oil diminished it. However, the insulinaemic response to mashed potato with chicken breast and rapeseed oil was lower than that to mashed potato alone. In conclusion, the protein, fat and salad contents of a meal exert considerable influence on the glycaemic and insulinaemic responses to mashed potatoes. Furthermore, the estimation of the GI of a mixed meal by calculation is imprecise.     

Effects of varying the carbohydrate:fat ratio in a hot lunch on postprandial variables in male volunteers

1. Healthy male volunteers consumed at noon, hot test meals with four different carbohydrate:fat ratios varying between 2.64 and 0.50, and composed of fried beefsteak, mashed potatoes, French beans, and a dessert of custard with mashed peaches. The energy content of the meals was 40% of the daily intake of the volunteers, estimated from their individual dietary histories. 2. Before, and at different times after the start of the meal, blood samples were taken and a number of indices of carbohydrate and lipid metabolism were determined in the samples, i.e. glucose, insulin, free fatty acid, free and total glycerol, free and total cholesterol, high-density-lipoprotein (HDL)-cholesterol and low-density-lipoprotein (LDL)-cholesterol. 3. Increasing the carbohydrate:fat ratio resulted in higher postprandial peaks of glucose and insulin. In addition, the peak area under the postprandial glucose curve showed a significant increase. The peak area under the postprandial insulin curve had also increased, indicating that a larger amount of insulin was secreted by the pancreas on increasing the carbohydrate content in the meal. There was no significant correlation between the height of the postprandial peak of blood glucose and the size of the meal. 4. All four meals caused elevated postprandial blood triacylglycerol levels. However, the decline of this elevated level took a much longer time after the meals with the lower carbohydrate:fat ratios, i.e. containing larger amounts of triacylglycerols. There was a significant decreasing linear relation between the carbohydrate content of the meals and the peak area under the postprandial triacylglycerol curve. Free glycerol and free fatty acids showed lower postprandial levels in the blood after the meals with the higher carbohydrate:fat ratios, and the peak areas of the postprandial curves of both variables displayed a significant decrease. Little or no effect of the meal carbohydrate:fat ratio was observed on the postprandial concentrations of total cholesterol, unesterified cholesterol, HDL-cholesterol or LDL-cholesterol.     

Effects of protein on glycemic and incretin responses and gastric emptying after oral glucose in healthy subjects

BACKGROUND: Dietary interventions represent a promising therapeutic strategy to optimize postprandial glycemia. The addition of protein to oral glucose has been reported to improve the glycemic profile. OBJECTIVE: The aim of the current study was to evaluate the mechanisms by which protein supplementation lowers the blood glucose response to oral glucose. DESIGN: Nine healthy men were studied on 3 d each in a random order. Subjects consumed 300-mL drinks containing either 50 g glucose (Glucose), 30 g gelatin (Protein), or 50 g glucose with 30 g gelatin (Glucose + Protein) in water labeled with 150 mg [(13)C]acetate. Blood and breath samples were subsequently collected for 3 h to measure blood glucose and plasma insulin, glucagon-like peptide 1 (GLP-1), and glucose-dependent insulinotropic polypeptide (GIP) concentrations and gastric half-emptying time, which was calculated from (13)CO(2) excretion. RESULTS: The blood glucose response was less after Glucose + Protein than after Glucose (P < 0.005); GIP was lower (P < 0.005), and there were no significant differences in plasma insulin or GLP-1. Protein alone stimulated insulin, GLP-1, and GIP (P < 0.05 for each) without elevating blood glucose. The gastric half-emptying time was greater after Glucose + Protein than after Glucose (P < 0.05) and tended to be greater for Glucose than for Protein (P = 0.06). CONCLUSIONS: In healthy humans, the addition of protein to oral glucose lowers postprandial blood glucose concentrations acutely, predominantly by slowing gastric emptying, although protein also stimulates incretin hormones and non-glucose-dependent insulin release.     

Different effects of whole milk and a fermented milk with the same fat and lactose content on gastric emptying and postprandial lipaemia, but not on glycaemic response and appetite

Longitudinal studies indicate that milk and fermented milk products lower basal plasma cholesterol concentrations, despite their high content of saturated fat, and therefore have favourable health effects. However, there have been few studies on the postprandial effects of milk products. The present study compared the effect of whole milk with a fermented milk, A-38, on postprandial carbohydrate and lipid metabolism, gastric emptying and appetite. Eight healthy young men participated. On the two test days, they arrived fasting for collection of baseline values before consuming the meals, which for a 75 kg subject consisted of 1.4 litre milk or fermented milk, plus 165 mg [13C]acetate (for later determination of gastric emptying by a [13C]acetate breath test). Lactose (15 g) was added to the A-38 meal to equalize the lactose content. Postprandially the A-38 meal resulted in a slower gastric emptying rate than milk (P<0.001). Furthermore, the A-38 meal resulted in a greater increase and a quicker decrease of the triacylglycerol content in all lipoprotein fractions (LDL-fraction, P<0.05; other fractions, P<0.001) and of the gastrointestinal hormones (cholecystokinin and peptide YY, P<0.05; gastric inhibitory polypeptide and glucagon-like polypeptide-1, P<0.001). There were no significant differences in appetite sensations (measured by visual analogue scale) or in the glucose and insulin response (P>0.10). The slower emptying rate of the liquid phase after the A-38 meal is probably due to the higher viscosity of A-38. The lower and more prolonged triacylglycerol response after the milk meal might be caused by coagulation of milk in the stomach.     

Postprandial thermogenesis in lean and obese subjects after meals supplemented with medium-chain and long-chain triglycerides

The thermic effect of medium-chain triglycerides (MCTs) was studied in six lean and six obese young males by evaluating postprandial thermogenesis (PPT) after the ingestion of mixed meals containing either 38 g long-chain triglycerides (LCTs) or 30 g MCTs plus 8 g LCTs. Postabsorptive resting metabolic rate (RMR) was higher (P less than 0.05) in the obese individuals than in the lean ones. PPT, evaluated as 6-h incremental areas above RMR, was greater (P less than 0.05) in both groups after meals containing MCTs. The thermic effect of MCTs was 119.7 +/- 33.9 and 144.7 +/- 48.8 kJ/6 h in the lean and the obese subjects, respectively. The postprandial response of glucose, insulin, and free fatty acids did not depend on the type of oil contained in the meal. Our study shows that PPT is enhanced in both lean and obese subjects when LCTs in a mixed meal are replaced with MCTs.     

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.     

Dietary supplementation with hydroxypropyl-distarch phosphate from waxy maize starch increases resting energy expenditure by lowering the postprandial glucose-dependent insulinotropic polypeptide response in human subjects

The aim of the present study was to investigate the effects of hydroxypropyl-distarch phosphate (HDP) supplementation on postprandial energy metabolism and glucose-dependent insulinotropic polypeptide (GIP) in human subjects. A total of ten healthy male subjects, with a mean BMI of 23·6 (SEM 1·3) kg/m(2), age 35·2 (SEM 1·9) years and body weight 71·1 (SEM 4·0) kg, participated in a randomised, cross-over, intervention study with two different test meals (1673·6 kJ) containing either waxy maize starch or HDP from waxy maize starch (degree of substitution 0·154, P content 0·004 %). Resting energy expenditure (REE) and blood concentrations of various biomarkers were measured at fasting and up to 180 min postprandially. Indirect calorimetry showed that the HDP meal caused higher REE (P < 0·05) and fat utilisation (P < 0·001) than the waxy maize starch meal. The HDP meal led to significantly lower postprandial glucose (P < 0·05), insulin (P < 0·05) and GIP (P < 0·05) responses than the waxy maize starch meal. Both postprandial REE (R - 0·576, P < 0·01) and fat utilisation (R - 0·514, P < 0·05) were negatively correlated with the postprandial GIP response, but not with the glucose and insulin responses. In conclusion, dietary supplementation with HDP lowers postprandial GIP and increases postprandial REE and fat utilisation in healthy humans. An HDP-rich diet may therefore have beneficial implications in weight management. Further studies are required to confirm the efficacy in overweight or obese subjects, and to determine the precise mechanisms.     

Meal size and frequency: effect on the thermic effect of food

The effects of meal size and frequency on thermic effect of food (TEF) were examined in seven healthy normal-weight young women. Each volunteer consumed in random order one of two identical meals [3138 kJ (750 kcal), 54.5% carbohydrate, 14.0% protein, 31.5% fat]. One meal was taken over 10 min [large meal (LM)] whereas the other was taken in six equal portions of 523 kJ (125 kcal) at 30-min intervals over a 3-h period [small meals (SM)]. Metabolic rate was measured for 1 h before and every 30 min after the meal started for 5 h. When expressed as either kJ/min (kcal/min) or kJ/5h (kcal/5h), TEF was significantly higher in the LM day than in the SM day (P less than 0.05). We conclude that the temporal pattern in which a mixed caloric load is eaten affects the thermogenic response and may be an important determinant of energy balance after a meal.     

The effect of low and moderate fat intakes on the postprandial lipaemic and hormonal responses in healthy volunteers.

Present literature indicates that whereas an acute fat intake of 5 g does not elicit a postprandial triacylglycerolaemic response, 20 g of fat does. Since 67% of fat intake occasions involve fat doses of less than 20 g, the present study examined the effect of a relatively low-fat (LF) meal (0.2 g/kg body weight; mean 14 g) on postprandial triacylglycerol (TAG) metabolism, compared with a high-fat (HF) meal (0.6 g/kg body weight; mean 43 g), a fat dose which is more typical of laboratory studies. Plasma- and chylomicron-TAG concentrations increased significantly (P < or = 0.001) following both meals, and the increase was significantly (P < or = 0.02) greater after the HF meal. The postprandial areas under the curves and maximal postprandial TAG concentrations for plasma- and chylomicron-TAG were significantly higher following the HF meal (P < or = 0.05). Postprandial plasma insulin and gastric inhibitory polypeptide concentrations increased significantly (P < or = 0.001) after each meal, but there was no difference between the two meals. These data show that modest amounts of fat in a meal will elicit a measurable postprandial TAG response. Since postprandial lipaemia affects the composition and concentration of the TAG- and cholesterol-rich lipoproteins, controlling dietary TAG supply may influence the metabolic fate of these lipoproteins.     

Ingestion of thermally oxidized sunflower oil decreases postprandial lipemia mainly in younger individuals

Animal studies have shown that diets rich in thermally oxidized fat increase glucose and decrease insulin and triglyceride (TG) concentrations in the blood. We hypothesized that ingestion of a potato meal rich in thermally oxidized sunflower oil (TOSO) would decrease postprandial concentrations of insulin, incretins, and TG and increase plasma glucose concentrations. Twenty healthy subjects aged 22 to 70 years consumed meals rich in TOSO or unheated sunflower oil and containing paracetamol (1.5 g) in a randomized, crossover trial. Blood samples were taken at baseline and 10, 20, 30, 60, 90, and 120 minutes after the meals and glucose, insulin, TG, nonesterified fatty acids, glucagon-like polypeptide-1, glucose-independent polypeptide, and paracetamol (as a marker of gastric emptying) were measured in plasma or serum. The incremental areas under the curve of glucose, insulin, nonesterified fatty acid, incretins, and paracetamol levels were not significantly different between the meals. Plasma TG incremental area under the curve was 44% lower after the TOSO meal at a marginal level of significance (P = .06) in the total study population and was significantly (P = .04) and 61% lower in those of median age and younger (n = 11). These data suggest that ingestion of TOSO may acutely decrease plasma TG mainly in younger individuals and does not acutely affect glucose and insulin metabolism or gastric emptying in healthy subjects.     

Thermic effect of food in man: effect of meal composition, and energy content

The effect of meal composition and energy content on the thermic effect of food (TEF) was investigated in sixteen adult, non-obese female subjects. Each subject consumed four different test meals, each meal on a different day. Meals were of high-carbohydrate-low-fat (HCLF) with 0.70, 0.19 and 0.11 of the energy content from carbohydrate, fat and protein respectively, and low-carbohydrate-high-fat (LCHF) with 0.24, 0.65 and 0.11 of the energy content from carbohydrate, fat and protein respectively. The energy contents of the test meals for each composition were 2520 kJ (600 kcal) and 5040 kJ (1200 kcal). The basal metabolic rate (BMR) and the postprandial metabolic rate (PP-MR) were measured by open-circuit indirect calorimetry using the Douglas bag technique while the subjects were in the supine position. The mean BMR value was 3.63 (SE 0.07) kJ/min (0.87 kcal/min (SE 0.017)). The 5 h-TEF value for the 2520 kJ (600 kcal) HCLF meal was 228 (SE 11.8) kJ (54 kcal (SE 2.8)) and for the LCHF meal was 228 (SE 9.6) kJ (54 kcal (SE 2.3)). The corresponding values for the 5040 kJ (1200 kcal) meals were 356 (SE 20.4) kJ (85 kcal (SE 4.9)) and 340 (SE 15.8) kJ (81 kcal (SE 3.8)). There was no significant (P = 0.49) effect of meal composition on TEF, but the energy content of the meals had a significant (P less than 0.001) effect on TEF. In all subjects and for all meals, PP-MR had not returned to premeal level 5 h after a meal, indicating that the TEF values measured underestimate total TEF. The present study suggests that TEF is significantly influenced by the energy content of a meal but not by meal composition.