Postprandial Substrate Oxidation Research Articles

Substrate metabolism in male astronauts onboard the International Space Station: the ENERGY study

Bedrest shifts fasting and postprandial fuel selection towards carbohydrate use over lipids, potentially affecting astronauts’ performance and health. We investigated whether this change occurs in astronauts after at least 3 months onboard the International Space Station (ISS). We further explored the associations with diet, physical activity (PA), and body composition. Before and during spaceflight, respiratory quotient (RQ), carbohydrate, and fat oxidation were measured by indirect calorimetry before and following a standardized meal in 11 males (age = 45.7 [SD 7.7] years, BMI = 24.3 [2.1] kg m−²). Postprandial substrate use was determined by 0-to-260 min postprandial incremental area under the curve (iAUC) of nutrient oxidation and the difference between maximal postprandial and fasting RQ (ΔRQ). Food quotient (FQ) was calculated from diet logs. Fat (FM) and fat-free mass (FFM) were measured by hydrometry and PA by accelerometry and diary logs. Spaceflight increased fasting RQ (P = 0.01) and carbohydrate oxidation (P = 0.04) and decreased fasting lipid oxidation (P < 0.01). An increase in FQ (P < 0.001) indicated dietary modifications onboard the ISS. Spaceflight-induced RQ changes adjusted for ground RQ correlated with inflight FQ (P < 0.01). In postprandial conditions, nutrient oxidation and ΔRQ were unaffected on average. Lipid oxidation changes negatively correlated with FFM changes and inflight aerobic exercise and positively with FM changes. The opposite was observed for carbohydrate oxidation. ΔRQ changes were negatively and positively related to FM and FFM changes, respectively. In conclusion, fasting substrate oxidation shift observed during spaceflight may primarily result from dietary modifications. Between-astronaut variability in postprandial substrate oxidation depends on body composition changes and inflight PA.

A Single Bout of Upper-Body Exercise Has No Effect on Postprandial Metabolism in Persons with Chronic Paraplegia.

ABSTRACTPurposeThe acute effects of a single bout of upper-body exercise on postprandial metabolism in persons with spinal cord injury are currently not well understood. The primary aim of this study was to evaluate the effects of a single bout of upper-body high-intensity interval exercise (HIIE) and moderate-intensity continuous exercise (MICE) in comparison with a no-exercise control (REST) condition on postprandial metabolic responses in persons with chronic paraplegia.MethodsTen participants (eight males, two females; age, 49 ± 10 yr; time since injury, 22 ± 13 yr) with chronic paraplegia took part in a randomized crossover study, consisting of three trials: HIIE (8 × 60 s at 70% peak power output [PPEAK]), MICE (25 min at 45% PPEAK), and REST, at least 3 d apart. Exercise was performed in the fasted state, and participants consumed a mixed-macronutrient liquid meal 1-h postexercise. Venous blood and expired gas samples were collected at regular intervals for 6-h postmeal consumption.ResultsThere were no significant differences in postprandial incremental area under the curve for triglycerides (P = 0.59) or glucose (P = 0.56) between conditions. Insulin incremental area under the curve tended to be lower after MICE (135 ± 85 nmol·L−1 per 360 min) compared with REST (162 ± 93 nmol·L−1 per 360 min), but this did not reach statistical significance (P = 0.06, d = 0.30). Participants reported a greater fondness (P = 0.04) and preference for HIIE over MICE.ConclusionsAfter an overnight fast, a single bout of upper-body exercise before eating has no effect on postprandial metabolism in persons with chronic paraplegia, irrespective of exercise intensity. This suggests that alternative exercise strategies may be required to stimulate postprandial substrate oxidation for this population.

Lactose and Digestible Maltodextrin in Milk Replacers Differently Affect Energy Metabolism and Substrate Oxidation: A Calorimetric Study in Piglets

Background:In recent years, lactose-free infant formulas have been increasingly used. Digestible maltodextrins are commonly used as a substitute for lactose in these formulas, but the effects on energy metabolism are unknown. Objective:We aimed to evaluate the differences in energy metabolism and substrate oxidation in piglets fed milk replacers containing lactose compared with maltodextrin as the only source of carbohydrates. Methods:Piglets (Tempo × Topigs 20) from 8 litters were fed milk replacers containing lactose or maltodextrin (28% w/w, milk powder basis) from 1 to 9 wk of age (n = 4 litters/milk replacer). At 5 wk of age, 4 females and 4 entire males (mean ± SEM bodyweight, 10 ± 0.3 kg) were selected per litter, and housed in 16 groups of 4 littermates, with 2 females and 2 males per pen (n = 8 groups/milk replacer). Between 7 and 9 wk of age, groups were housed for 72 h in climate respiration chambers, and fed their experimental milk replacer in 2 meals per day, at 08:30 and 16:30. Heat production data were calculated from the continuous measurement of gaseous exchanges and analyzed using general linear models in SAS. Results:Resting metabolic rate was 6% less in maltodextrin- than in lactose-fed piglets, notably before the morning meal. The postprandial respiratory quotient was 13% greater in maltodextrin- than in lactose-fed piglets after both meals. Net rates of carbohydrate oxidation were on average 5% greater in maltodextrin- than in lactose-fed piglets, particularly after the afternoon meal, whereas net rates of fat oxidation were 9% less in maltodextrin- than in lactose-fed piglets, particularly after the morning meal. Conclusions:Compared with lactose, maltodextrin in milk replacers reduced resting metabolic rate in the fasting state, and induced a shift in postprandial substrate oxidation profiles in pigs. Further research is warranted to evaluate the consequences of these metabolic changes for body composition.

1865-P: SGLT2 Inhibition Compared with Iso-energetic/Low-Carbohydrate Diet Reprograms Systemic Substrate Oxidation in Type 2 Diabetes

Introduction: Pharmacologic inhibition of the renal sodium/glucose cotransporter-2 (SGLT2i) facilitates lipid oxidation. Iso-energetic/low-carbohydrate diet (i-Carbo) eliminates the same amount of glucose as SGLT2 inhibition (∼ 50 g/day of glucose). We examined whether i-Carbo and SGLT2i may have any impact, on 1) fasting and postprandial energy expenditure (EE) and substrate oxidation, 2) the basal-bolus dose of insulin that achieve euglycemia. Method: Twenty four T2D (M/F = 15/9, age 53.6 ± 14.2, BMI 26.9 ± 4.8 kg/m2, HbA1c 12.5 ± 1.6 %) were enrolled to this 12 weeks, randomized, 3 arms open-label, prospective study with basal-bolus insulin titration algorithm, control diet (CON) or adding canagliflozin 100 mg/day to CON (SGLT2i) and the i-Carbo. We measured indirect calorimetry to provide EE and respiratory quotient (RQ) during fasting and postprandial before and after the intervention. Results: In spite of similar carbohydrate amount in the i-Carbo, compared to the SGLT2i, the total daily dose of insulin was significantly higher (p=0.02). Compared to the CON, fasting EE were similar on both SGLT2i and i-Carbo, however, postprandial EE were elevated, respectively (p=0.03, 0.04). Fasting RQ was marginally higher in SGLT2i compared to the CON (p=0.049). Postprandial RQ was elevated by means of increased carbohydrate substrate utilization on both SGLT2i (p=0.04) and i-Carbo (p=0.03) groups compared to the CON. Conclusion: Iso-energetic/low-carbohydrate in i-Carbo, which matches urinary carbohydrate loss in SGLT2i, had similar fasting and postprandial energy expenditure and substrate oxidation rate. Increased insulin requirement in i-Carbo indicates that relative high lipid and protein ratio, compared to SGLT2i, may have any effect to insulin requirement. Disclosure H. Igarashi: None. H. Uchino: None. M. Furuta: None. M. Miyagi: None. N. Kumashiro: Research Support; Self; Boehringer Ingelheim Pharmaceuticals, Inc. Speaker’s Bureau; Self; Novo Nordisk Inc., Ono Pharmaceutical Co., Ltd., Takeda Pharmaceutical Company Limited. T. Hirose: Research Support; Self; Boehringer Ingelheim Pharmaceuticals, Inc., Daiichi Sankyo, Mitsubishi Tanabe Pharma Corporation, Ono Pharmaceutical Co., Ltd., Takeda Pharmaceutical Company Limited. Speaker’s Bureau; Self; AstraZeneca, Lilly Diabetes, Novo Nordisk Inc., Sanofi, Sumitomo Dainippon Pharma Co., Ltd.

Tabata style functional exercise increases resting and postprandial fat oxidation but does not reduce triglyceride concentrations

We evaluated the effect of a high fat meal with and without prior high intensity functional exercise executed in a Tabata style interval pattern on resting and postprandial substrate oxidation, to include blood glucose and triglyceride concentrations in humans. Eleven healthy males completed two trials [Tabata exercise (TE) and non‐exercise control (CON)] in random order separated by 7 days. A two‐day protocol was used in which TE or CON was performed on the first day and a high fat meal was administered ~13 hrs later on the following morning. Power output from the TE session was quantified using a kinematic approach by calculating external work performed per unit of time for each of the 4 exercises (rowing, dumbbell thrusters, kettlebell swings, and burpees). For the meal challenge, respiratory gases and blood samples were taken fasted and at 1, 2, and 3 hrs postprandial. Fat oxidation was significantly higher after TE compared to CON at each time point (P &lt; 0.05). Total fat oxidized, total fat oxidation AUC, and total postprandial fat oxidized all significantly increased after TE (P &lt; 0.05). Carbohydrate oxidation was significantly lower after TE compared to CON at 1 hr postprandial (P &lt; 0.05). Total carbohydrate oxidized, total carbohydrate oxidation AUC, and total postprandial carbohydrate oxidized all significantly decreased after TE (P &lt; 0.05). There were no significant effects of TE on fasting or postprandial glucose or triglyceride concentrations. Functional exercises performed in a high intensity TE pattern enhance fasting and postprandial fat oxidation on the following day with minimal influence on blood triglycerides or glucose levels.Support or Funding InformationR.C.P. was support by the University of Georgia Graduate School Georgia Research Education Award Traineeship Follows Program

Tabata‐style functional exercise increases resting and postprandial fat oxidation but does not reduce triglyceride concentrations

What is the central question of this study? What are the metabolic impacts of high intensity functional Tabata exercise? What is the main finding and its importance? Tabata exercise with high intensity functional movements causes increases in fasted and postprandial fat oxidation the day after exercise without altering postprandial triglyceride concentrations. These results support the usage of a Tabata-style high intensity functional exercise to improve postprandial fat oxidation. We evaluated the effect of a high fat meal with and without prior high intensity functional exercise executed in a Tabata-style interval pattern on resting and postprandial substrate oxidation, as well as postprandial blood glucose and triglyceride concentrations. Eleven healthy males completed two trials (Tabata exercise (TE) and non-exercise control (CON)) in random order separated by 7days. A two-day protocol was used in which TE or CON was performed on the first day and a high fat meal was administered ∼13h later the following morning. Power output from the TE session was quantified using a kinematic approach by calculating external work performed per unit time for each of the four exercises (rowing, dumbbell thrusters, kettlebell swings and burpees). For the meal challenge, respiratory gases and blood samples were taken fasted and at 1, 2 and 3h postprandial. Fat oxidation was significantly higher after TE compared to CON at all time points (P<0.05). Carbohydrate oxidation was significantly lower after TE compared to CON at 1h postprandial (P<0.05). There were no significant effects of TE on fasting or postprandial glucose or triglyceride concentrations. Functional exercises performed in a high intensity TE pattern enhance fasting and postprandial fat oxidation on the following day with minimal influence on blood triglycerides or glucose levels.

Similarities in Metabolic Flexibility and Hunger Hormone Ghrelin Exist between FTO Gene Variants in Response to an Acute Dietary Challenge

The rs9939609 polymorphism of the fat mass and obesity-associated (FTO) gene has been associated with obesity, and studies have also shown that environmental/lifestyle interaction such as dietary intake might mediate this effect. The current study investigates the postprandial hormonal regulators of hunger and indirect markers of substrate utilisation and metabolic flexibility following a dietary challenge to determine if suppression of circulating ghrelin levels and/or reduced metabolic flexibility exist between FTO genotypes. One hundred and forty seven healthy, sedentary males and females (29.0 ± 0.7 yrs; 70.2 ± 1.1 kg; 169.1 ± 0.8 cm; 24.5 ± 0.3 kg/m2) complete a single experimental session. Anthropometric measures, circulating levels of active ghrelin, insulin and glucose, and substrate oxidation via indirect calorimetry, are measured pre-prandial and/or post-prandial. The FTO rs9939609 variant is genotyped using a real-time polymerase chain reaction. Metabolic flexibility (∆RER) is similar between FTO genotypes of the rs9939609 (T > A) polymorphism (p > 0.05). No differences in pre-prandial and/or postprandial substrate oxidation, plasma glucose, serum insulin or ghrelin are observed between genotypes (p > 0.05). These observations are independent of body mass index and gender. Altered postprandial responses in hunger hormones and metabolic flexibility may not be a mechanism by which FTO is associated with higher BMI and obesity in healthy, normal-weighted individuals.

A Single Dose of Goji Berries Does Not Affect Postprandial Energy Expenditure and Substrate Oxidation in Healthy, Overweight Men.

Background and Aim Increasing energy expenditure is an effective strategy for the prevention of obesity. In this respect, Lycium barbarum (goji berry) is of interest, as it has been shown to increase postprandial oxygen consumption. Although this suggests that energy expenditure was also increased, energy expenditure and substrate oxidation can only be assessed accurately when both oxygen consumption and carbon dioxide production are measured. We therefore investigated the effects of a single dose of Lycium barbarum fruit on postprandial energy expenditure and substrate oxidation in a randomized, double-blind crossover trial. In addition, markers of lipid and glucose metabolism were measured. Methods Seventeen healthy, overweight men received in a random order a meal containing 25 grams of dried Lycium barbarum fruit or a control meal matched for caloric content and macronutrient composition. Energy expenditure and the respiratory quotient were determined using indirect calorimetry before and up to 4 hours after meal intake. Blood was sampled before and after meal intake at regular intervals for analyses of plasma glucose, serum triacylglycerol, and free fatty acid concentrations. Results Energy expenditure significantly increased after the Lycium barbarum and control meal, but no differences were found between the meals (p=0.217). Postprandial changes in respiratory quotient (p=0.719) and concentrations of glucose (p=0.663), triacylglycerol (p=0.391), and free fatty acids (p=0.287) were also not affected by Lycium barbarum intake. Conclusions A single dose of Lycium barbarum does not affect postprandial energy expenditure, substrate oxidation, and markers for lipid and glucose metabolism in healthy, overweight men.

Phosphorus ingestion with a high-carbohydrate meal increased the postprandial energy expenditure of obese and lean individuals.

Phosphorus ingestion with glucose was reported to stimulate the postprandial peripheral uptake of both phosphorus and glucose, a process that favors energy production. The aim of this study was to determine whether phosphorus ingestion with a meal can affect energy metabolism. Overnight fasted men (eight lean and seven obese) consumed a high-carbohydrate meal (648 kcal) with either placebo or phosphorus (500 mg) tablets in a random order. Energy expenditure and substrate oxidation were monitored for 240 min using ventilated hood indirect calorimetry. Phosphorus ingestion with a meal increased the postprandial energy expenditure of both lean and obese individuals (P < 0.001), although in different patterns. Alterations in postprandial substrate oxidation was highly noticeable from time 120 min onward, where phosphorus-treated lean participants exhibited a significant decrease in respiratory quotient. Phosphorus ingestion with a high-carbohydrate meal alters postprandial energy metabolism mainly by enhancing postprandial energy expenditure that may ultimatly favor weight loss.

Postprandial energy metabolism and substrate oxidation in response to the inclusion of a sugar- or non-nutritive sweetened beverage with meals differing in protein content

BackgroundThe macronutrient composition of the diet may play a more important role in maintaining a healthy body weight and preventing obesity than previously thought. The primary goal of this research was to determine the extent to which the simple addition of a small serving of a sugar-sweetened beverage (SSB) to meals with different macronutrient compositions impacts appetite, energy metabolism and substrate oxidation.MethodsAppetite, energy metabolism and substrate oxidation were measured in 27 healthy weight adults (age = 23 ± 5 y; BMI = 23 ± 2 kg/m2) on two occasions in a room calorimeter after consuming a SSB or a non-nutritive-sweetened beverage (NNSB) with a standard (15%E) or high- (30%E) protein meal. Meal carbohydrate (CHO) content was adjusted to maintain equivalent calories for both study visits. All meals were composed of the same foods and provided 17 g of fat and 500 non-beverage calories. Study visits were separated by at least 1 week and menstruating females were studied during the luteal phase (Days 15–20). The effects of sex, protein level and beverage type and their interactions on satiety, appetite for foods with specific taste profiles, diet-induced thermogenesis (DIT) and rates of substrate oxidation were assessed using a 3-way Repeated Measures Analysis of Variance.ResultsIncreasing dietary protein decreased hunger and increased satiety. Males were hungrier and less satisfied with the meals than females. Increasing dietary protein also decreased the desire to eat something savory, salty and fatty and the males had a greater appetite for food with these taste profiles. Interestingly, there was no effect of sex, dietary protein or beverage type on the desire to eat something sweet. The inclusion of a SSB markedly suppressed DIT (2.42% ± 5.91%) and fat oxidation (9.87 ± 11.09 g).ConclusionAppetite sensations, food preferences, energy expenditure and substrate oxidation are significantly altered in response to changes in meal macronutrient composition produced by modifications in the protein content of a meal and consumption of a SSB. Most notably, consumption of a SSB during a meal markedly reduces energy efficiency and fat oxidation independent of macronutrient composition.Trial registrationsClinicalTrials.gov: NCT02211599, registered August 05, 2014.

Does the ingestion of a 24\xa0hour low glycaemic index Asian mixed meal diet improve glycaemic response and promote fat oxidation? A controlled, randomized cross-over study

BackgroundThe health benefits of consuming a low glycaemic index (GI) diet to reduce the risk of type 2 Diabetes are well recognized. In recent years the GI values of various foods have been determined. Their efficacy in constructing and consuming a low GI diet over 24 h in modulating glycaemic response has not been fully documented. The translation of using single-point GI values of foods to develop a 24 h mixed meal diet can provide valuable information to consumers, researchers and dietitians to optimize food choice for glycaemic control. By using GI values of foods to develop mixed meals, our study is the first to determine how both blood glucose and substrate oxidation may be modulated over 24 h.MethodsThe study included 11 Asian men with a BMI between 17–24 kg/m2 who followed both a 1-day low GI and 1-day high GI diet in a randomized, controlled cross-over design. Test meals included breakfast, lunch, snack and dinner. Glycaemic response was measured continuously for over 24 h and postprandial substrate oxidation for 10 h inside a whole body calorimeter.ResultsThe low GI diet resulted in lower 24 h glucose iAUC (860 ± 440 vs 1329 ± 614 mmol/L.min; p = 0.014) with lower postprandial glucose iAUC after breakfast (p < 0.001), lunch (p = 0.009), snack (p = 0.012) and dinner (p = 0.003). Moreover, 24 h mean amplitude of glycaemic excursion was lower during the low GI vs high GI diet (1.44 ± 0.63 vs 2.33 ± 0.82 mmol/L; p < 0.001). Simultaneously, decrease in 10 h fat oxidation was less during the low vs high GI diet (−0.033 ± 0.021 vs −0.050 ± 0.017 g/min; p < 0.001), specifically after breakfast (p < 0.001) and lunch (p < 0.001).ConclusionsOur study corroborates that using low GI local foods to construct a 24 h low GI diet, is able to reduce glycaemic response and variability as recorded by continuous glucose monitoring. Our observations also confirm that a low GI diet promotes fat oxidation over carbohydrate oxidation when compared to a high GI diet. These observations provide public health support for the encouragement of healthier nutrition choices by consuming low GI foods.Trial registrationNCT 02631083 (Clinicaltrials.gov).

Metabolic responses to dietary fatty acids in obese women

BackgroundThe composition of fatty acids in a diet may differentially affect metabolism, thus playing a role in the development of obesity. Our purpose was to study the effects of three high-fat (HF) meals with different dietary fatty acid compositions on the thermic effect of meal (TEM) and substrate oxidation in obese premenopausal women. Methods16 healthy obese women, aged 18–39years, participated in a single-blinded randomized cross-over study, in which they consumed isocaloric HF meals (70% of energy from fat) rich in either saturated fat (SFA), monounsaturated fat (MUFA) or polyunsaturated fat (PUFA). Indirect calorimetry was used to measure respiratory gases for a 5-hour postprandial period. Data collected was used to determine respiratory exchange ratio (RER) for assessing substrate oxidation, and energy expenditure for the determination of TEM. ResultsThere was a significant time effect on both substrate oxidation and TEM (p<0.05). With and without using RMR as a covariate, there were no significant differences in TEM between test meals (TEM of 10.8±0.8 vs 11.0±1.0kcal∗5h for high-MUFA vs. high-SFA meals, respectively, p=0.06). No treatment difference was found for postprandial substrate utilization (4.9±0.4, 4.9±0.3 and 4.6±0.4g of fat oxidation following SFA, MUFA, and PUFA-rich HF meals, respectively; 13.2±0.9, 13.3±0.5 and 13.9±0.6g of carbohydrate oxidation following SFA, MUFA, and PUFA-rich HF meals, respectively). ConclusionsIn premenopausal obese women, HF meals rich in either MUFAs, PUFAs, or SFAs did not differentially affect TEM or postprandial substrate oxidation.

PP002-SUN: Outstanding abstract: Postprandial Thermogenesis and Substrate Oxidation in Response to Galactose – The Forgotten Sugar: Comparison with Glucose and Fructose in Healthy Young Adults

PP002-SUN: Outstanding abstract: Postprandial Thermogenesis and Substrate Oxidation in Response to Galactose – The Forgotten Sugar: Comparison with Glucose and Fructose in Healthy Young Adults

Postprandial thermogenesis and substrate oxidation are unaffected by sleep restriction

Background/ObjectivesThe extent to which alterations in energy expenditure (EE) in response to sleep restriction contribute to the short sleep-obesity relationship is not clearly defined. Short sleep may induce changes in resting metabolic rate (RMR), thermic effect of food (TEF), and postprandial substrate oxidation.Subjects/MethodsTen females (age and BMI: 22-43 y and 23.4-28 kg/m2) completed a randomized, crossover study assessing the effects of short (4 h/night) and habitual (8 h/night) sleep duration on fasting and postprandial RMR and respiratory quotient (RQ). Measurements were taken after 3 nights using whole-room indirect calorimetry. The TEF was assessed over a 6-h period following consumption of a high-fat liquid meal.ResultsShort vs. habitual sleep did not affect RMR (1.01 ± 0.05 and 0.97 ± 0.04 kcal/min; p=0.23). Fasting RQ was significantly lower after short vs. habitual sleep (0.84 ± 0.01 and 0.88 ± 0.01; p=0.028). Postprandial EE (short: 1.13 ± 0.04 and habitual: 1.10 ± 0.04, p=0.09) and RQ (short: 0.88 ± 0.01 and habitual: 0.88 ± 0.01, p=0.50) after the high-fat meal were not different between conditions. TEF was similar between conditions (0.24 ± 0.02 kcal/min in both; p=0.98), as was the ~6-h incremental area under the curve (1.16 ± 0.10 and 1.17 ± 0.09 kcal/min x 356 min after short and habitual sleep, respectively; p=0.92).ConclusionsCurrent findings observed in non-obese healthy premenopausal women do not support the hypothesis that alterations in TEF and postprandial substrate oxidation are major contributors to the higher rate of obesity observed in short sleepers. In exploring a role of sleep duration on EE, research should focus on potential alterations in physical activity to explain the increased obesity risk in short sleepers.

Metabolic and hormonal consequences of two different meals after a moderate intensity exercise bout in obese prepubertal children

To investigate the relationship between postprandial nutrient balance, satiety and hormone changes induced by two different meals taken after a moderate intensity exercise bout. Ten prepubertal obese children participated in the study. The experiment was designed as a cross-over study for repeated measures. Each test period lasted five consecutive hours during which the children were under medical supervision. The effects of two isocaloric meals were compared after a moderate intensity exercise (4 multiples of resting metabolic rate, 30 min, cycling): a low-fat/high-carbohydrate meal (meal A) and a high-fat/low-carbohydrate meal (meal B). Pre and postprandial (3 h) substrate oxidation, biochemical parameters, gastrointestinal hormone concentrations and appetite were measured. The main results were: (i) higher fat balance (5.1±5.0 vs -5.0±6.6 g, P=0.001) and lower carbohydrate balance after meal B than A (-9.7±13.3 vs 11.3±18.3 g, P<0.01); (ii) higher energy balance after meal B than after meal A (5.9±21.5 vs -13.9±20.2 kcal, P<0.05); (iii) higher plasma triglyceride concentrations (area under the curve) after meal B than after meal A (2962.5±2095.8 mg*180 min/dl vs -169.5±1633.7 mg*180 min/dl, P<0.01); (iv) higher serum glucagon-like peptide-1 concentrations after meal B than after meal A (1101.5±873.0 pmol*180 min/l vs 478.8±638.3 pmol*180 min/l, P<0.05). After a bout of moderate intensity exercise, a meal with a high-fat/low-carbohydrate ratio had a less favorable metabolic impact than an isoenergetic, isoproteic low-fat/high-carbohydrate meal.

Change in postprandial substrate oxidation after a high-fructose meal is related to body mass index in healthy men

Oral fructose decreases fat oxidation and increases carbohydrate oxidation in obese subjects, but the metabolic response to fructose in lean individuals is less well understood. The purpose of this study was to assess the effects of a single fructose-rich mixed meal on substrate oxidation in young healthy nonobese men. We hypothesized that a decrease in fat oxidation and an increase in carbohydrate oxidation would be observed after a fructose-rich mixed meal compared with a glucose-rich mixed meal. Twelve healthy, normal weight to overweight, aged 23 to 31 years participated in a double-blind, crossover study. Each participant completed 2 study visits, eating a mixed meal containing 30% of the calories from either fructose or glucose. Blood samples for glucose, insulin, triglycerides, and leptin as well as gas exchange by indirect calorimetry were measured intermittently for 7 hours. Serum insulin was higher after a fructose mixed meal, but plasma glucose, plasma leptin, and serum triglycerides were not different. Mean postprandial respiratory quotient and estimated fat oxidation did not differ between the fructose and glucose meals. The change in fat oxidation between the fructose- and glucose-rich meals negatively correlated with body mass index (BMI; r = −0.59 [P = .04] and r = −0.59 [P = .04] at the 4- and 7-hour time points, respectively). In healthy nonobese men, BMI correlates with altered postprandial fat oxidation after a high-fructose mixed meal. The metabolic response to a high-fructose meal may be modulated by BMI.

A new indirect calorimeter is accurate and reliable for measuring basal energy expenditure, thermic effect of food and substrate oxidation in obese and healthy subjects

Summary Background & aims The objectives of the study were to validate accuracy and reliability of the QUARK RMR, an indirect calorimeter versus the DELTATRAC II™, a well-established reference system which is no longer available, in resting and post-prandial conditions. Methods A crossover, randomized study was performed in 30 subjects for two consecutive days. Resting metabolic rate (RMR) was measured for three 45 min periods using alternating calorimeters. Means of RMR were then compared with Pearson’s test and Bland and Altman plot. Thermic effect of food (TEF) and substrate oxidation were assessed for 3 h with each calorimeter, 15 min after meal ingestion, and were compared by longitudinal analysis. Results Means at rest of VO 2 , VCO 2 , RMR and substrate oxidation were not significantly different with both devices. The variability of VO 2 , VCO 2 and RMR measurements, at rest, for each device, on two consecutive days, was similar to that measured with QUARK RMR and DELTATRAC II™ the same day, under standardized conditions. Longitudinal analysis of TEF and post-prandial substrate oxidation was equivalent with the two devices. Conclusions The QUARK RMR calorimeter seems to be a valid system to measure energy expenditure in resting and post-prandial conditions in obese and healthy subjects. Clinical Trial Registration Number: NCT00848471.

A High‐fat vs. a Moderate‐fat Meal in Obese Boys: Nutrient Balance, Appetite, and Gastrointestinal Hormone Changes

Meal composition is a contributing factor to fat gain. In this study, we investigated the relationship between postprandial nutrient balance, satiety, and hormone changes induced by a high-fat meal vs. a moderate-fat meal. Ten prepubertal obese boys (BMI z-score range: 1.3-3.0) were recruited. Two meals (energy: 590 kcal) were compared: (i) high-fat (HF) meal: 12% protein, 52% fat, 36% carbohydrates; (ii) moderate-fat (MF) meal: 12% protein, 27% fat, 61% carbohydrates. Pre- and postprandial (5 h) substrate oxidation (indirect calorimetry), appetite (visual analogue scale), biochemical parameters and gastrointestinal hormone concentrations were measured. Carbohydrate balance was significantly (P < 0.001) lower (31.3 (5.7) g/5 h vs. 66.9 (5.9) g/5 h) and fat balance was significantly (P < 0.001) higher (11.5 (3.3) g/5 h vs. -0.7 (2.9) g/5 h) after HF than MF meal. Appetite (area under the curve (AUC)) was significantly reduced after an MF than an HF meal (494 (55) cm.300 min vs. 595 (57) cm.300 min, P < 0.05). Postprandial triglyceride concentration (AUC) was significantly (P < 0.05) higher after an HF than an MF meal: 141.1 (30.3) mmol.300 min/l vs. 79.3 (23.8) mmol.300 min/l, respectively. Peptide YY (PYY), cholecystokinin (CCK), and ghrelin concentrations (AUC) were not significantly different after an HF and MF meal. Glucagon-like peptide-1 (GLP-1) was significantly (P < 0.05) higher after an HF than after an MF meal (72.3 (9.8) ng/ml vs. 22.7 (7.6) ng/ml, respectively), but it did not affect subjective appetite. In conclusion, an MF meal induced a better postprandial metabolic nutrient balance, triglyceride levels, and appetite suppression than an HF meal. Gastrointestinal hormones were not related to clinically assessed hunger suppression after both meals.

High-level medium-chain triglyceride feeding and energy expenditure in normal-weight women

The objective of this study was to assess how short-term feeding of high levels of dietary medium-chain triglyceride (MCT) affect energy expenditure and postprandial substrate oxidation rates in normal-weight, premenopausal women. Eight healthy women were fed both a MCT-rich and an isocaloric long-chain triglyceride (LCT)-rich diet for two 1-week periods separated by a minimum of 21 days. The energy intake in each diet was 45% carbohydrates, 40% fat, and 15% protein. The 2 diets had either 60.81% or 1.11% of total fat energy from MCT with the remaining fat energy intake from LCT. On days 1 and 7 of each diet, resting metabolic rate and postprandial energy expenditure (EE) were measured by indirect calorimetry with a ventilated hood. Results indicated on days 1 and 7, there were no significant differences between diets for resting metabolic rate or mean postprandial EE. On both days 1 and 7, fat oxidation for the MCT-rich diet was significantly greater (0.0001 </= p </= 0.04) than that for the LCT-rich diet at different time points across the 5.5 h postprandial period. In conclusion, for premenopausal, normal-weight women consuming a diet with 25% of the energy content from MCT, there were no changes in resting metabolic rate, transient increases in postprandial energy expenditure, and significant increases in postprandial fat oxidation.

Ghrelin, insulin sensitivity and postprandial glucose disposal in overweight and obese children

To explore the changes of ghrelin circulating levels induced by a mixed meal and their relationship with postprandial substrate oxidation rates in overweight and obese children with different levels of insulin sensitivity. A group of ten boys (age 9-12 years) with different levels of overweight (standard deviation score of body mass index: 1.6-3.2) was recruited. Body composition was measured by dual-energy X-ray absorptiometry. Insulin sensitivity was assessed by a frequently sampled i.v. glucose tolerance test. Pre-prandial and postprandial (3 h) substrate oxidation was measured by indirect calorimetry. The energy content of the test meal (16% protein, 36% carbohydrate and 48% fat) was 40% of pre-prandial energy expenditure (kJ/day). Pre-prandial serum concentration of total ghrelin was 701.4+/-66.9 pg/ml (S.E.M.). The test meal induced a rapid decrease in ghrelin levels and maximal decrease was 27.3+/-2.7% below baseline. Meal intake induced a progressive increase of the carbohydrate oxidation rate for 45 min after food ingestion, followed by a slow decrease without returning to pre-prandial values. Postprandial cumulative carbohydrate oxidation was 16.9+/-0.8 g/3 h. Insulin sensitivity and postprandial maximal decrease of ghrelin concentration showed a significant correlation (r = 0.803, P < 0.01). Moreover, the postprandial carbohydrate oxidation rate correlated with the area under the curve for both insulin (r = 0.673, P < 0.03) and ghrelin (r = -0.661, P < 0.04). A relevant association between postprandial insulin-mediated glucose metabolism and ghrelin secretion in children with different levels of overweight was found. It is possible that the maintenance of an adequate level of insulin sensitivity and glucose oxidation may affect appetite regulation by favoring a more efficient postprandial ghrelin reduction.