CHO Meal Research Articles

A dairy-based, protein-rich breakfast enhances satiety and cognitive concentration before lunch in overweight to obese young females: A randomized controlled crossover study

The purpose of this study was to investigate if consumption of a high-protein, low-carbohydrate breakfast (PRO) leads to a lower subsequent ad libitum energy intake at lunch and the rest of the day compared with ingestion of an isocaloric low-protein, high-carbohydrate breakfast (CHO) or no breakfast (CON). The study was designed as a randomized controlled 3-period crossover study. Thirty young (18-30 yr) females with overweight to obesity (body mass index >25 kg/m2) in random order completed 3 separate experimental days where they consumed either a PRO, CHO, or CON breakfast test meal followed by an ad libitum lunch meal 3 h after breakfast. Participants were allocated to a sequence group by their inclusion number. The PRO and CHO breakfasts were matched in dietary fiber and fat content. Energy intake at lunch was calculated and dietary records were obtained for the rest of the day to calculate the total daily energy intake and macronutrient intake. Ratings of appetite sensations between meals and palatability of the test meals were assessed using visual analog scale sheets in intervals ranging from 10 to 30 min. In addition, blood samples were obtained at multiple time points separated by 10 to 60 min intervals between breakfast and lunch and were analyzed for appetite-regulating gut hormones, insulin, and glucose. Finally, performance in a cognitive concentration test was tested 150 min after breakfast. Compared with CHO and CON, the area under the curves for satiety, fullness, and satisfaction in the 3 h after breakfast were significantly higher after PRO, whereas the areas under the curve for hunger, desire to eat, and prospective eating were significantly lower after PRO. The appetite-regulating gut hormones cholecystokinin, glucagon-like peptide-1, and ghrelin in the hours after breakfast, energy intake during the ad libitum lunch meal, and the total daily energy intake did not differ significantly between PRO, CHO, and CON. However, the cognitive concentration test score was 3.5 percentage points higher for PRO, but not CHO, versus CON. A dairy-based high-protein, low-carbohydrate breakfast increased satiety sensation in the hours after breakfast but did not reduce total daily energy intake compared with an isocaloric low-protein, high-carbohydrate breakfast or omitting breakfast. However, performance in a cognitive concentration test before lunch was enhanced after the high-protein, low-carbohydrate breakfast, but not the low-protein, high-carbohydrate breakfast, compared with omitting breakfast.

The Impact of Pre-Exercise Carbohydrate Meal on the Effects of Yerba Mate Drink on Metabolism, Performance, and Antioxidant Status in Trained Male Cyclists

IntroductionThe consumption of yerba mate (YM), a source of antioxidants, in a fasted state increases fatty acid oxidation (FATox) during low–moderate-intensity exercise and improves performance in high-intensity exercise. However, the impact of a pre-exercise carbohydrate (CHO) meal on YM effects during exercise is unknown.ObjectiveWe investigated the effects of yerba mate drink (YMD) consumed in the fasted state (YMD-F) or after a CHO meal (YMD-CHO) on measurements of metabolism, performance, and blood oxidative stress markers in cycling exercise.MethodsIn a randomized, repeated-measures, crossover design, eight trained male cyclists ingested (i) YMD-CHO, (ii) YMD-F, or (iii) control-water and CHO meal (Control-CHO). The YMD (an infusion of 5 g of ultrarefined leaves in 250 mL of water) was taken for 7 days and 40 min before exercise. CHO meal (1 g/kg body mass) was consumed 60 min before exercise. The cycling protocol included a 40-min low-intensity (~ 53% V̇O2peak) constant load test (CLT); a 20-min time trial (TT); and 4 × 10-s all-out sprints. Blood samples and respiratory gases were collected before, during, and/or after tests.ResultsDuring CLT, YMD-CHO increased FATox ~ 13% vs. YMD-F (P = 0.041) and ~ 27% vs. Control-CHO (P < 0.001). During TT, YMD-CHO increased FATox ~ 160% vs. YMD-F (P < 0.001) and ~ 150% vs. Control-CHO (P < 0.001). Power output during TT improved ~ 3% (P = 0.022) in YMD-CHO vs. Control-CHO and was strongly correlated with changes in serum total antioxidant capacity (r = −0.87) and oxidative stress index (r = 0.76) at post-exercise in YMD-CHO. Performance in sprints was not affected by YMD.ConclusionCHO intake did not negate the effect of YMD on FATox or TT performance. Instead, a synergism between the two dietary strategies may be present.Clinical Trial Registration NCT04642144. November 18, 2020. Retrospectively registered.

Evaluation of a New Protocol of Insulin Dose Adjustment in a Low-Resource Setting

Glycemic control (GC) is difficult to achieve in settings where only NPH, R and pre-mixed insulins are available, test strips are scarce, and food insecurity is common. We evaluated the impact of a sliding-scale based insulin adjustment protocol in Haiti. Thirty youth aged 11-28 years with T1D treated with 70/30 Mixtard were randomized to remain on 70/30 (G70, n=15) or switch to self-mixed NPH+R (GNR, n=15). Carbohydrate (CHO) ratio and insulin sensitivity factor were calculated based on total daily insulin dose (TDD), and translated into sliding scales with either insulin correction dose (ICD) only (G70), or the sum of a 60 g CHO meal dose and ICD (GNR). Self-monitored blood glucose (SMBG) and insulin were administered before AM and PM meals. All had bi-monthly visits for 12 weeks. In G70 vs. GNR, age (19.3±4.5 vs. 19.2±5.4 years), sex (40 vs. 53% m), normal BMI (87 vs. 80%), diabetes duration (5.3±4.2 vs. 5.3±4.5 years), and baseline A1c (9.8±2.1 vs. 10.8±2.9%, p=0.27) did not differ. A1c declined to 8.0±1.3% (-1.8%, p&amp;lt;0.006) vs. 8.9±1.2% (-1.9%, p&amp;lt;0.02), p=0.83, without severe acute complication. Skipped meals per week (3.7±2.9 vs. 4.1±3.3), missed SMBG (3.5±3.4 vs. 7.4±7.6%, p=0.07), and increase of TDD (7.7±7.8 vs. 6.6±9.6 units) were similar. Use of sliding scales adjusted for SMBG and meals omission, and frequent clinic visits significantly improved GC in youth with T1D in a low-resource setting, regardless of pre- or self-mixed insulin. Disclosure E. Jean Baptiste: None. P. Larco: None. M. Charles Larco: None. J.E. von Oettingen: None. E. Dubois: None. R. Paul: None. E. Fleury-Milfort: None. R. Charles: None. G.D. Ogle: None.

Effect of mouth rinsing and ingestion of carbohydrate solutions on mood and perceptual responses during exercise

BackgroundThe aim of this study was to investigate whether mouth rinsing or ingesting carbohydrate (CHO) solutions impact on perceptual responses during exercise.MethodsNine moderately trained male cyclists underwent a 90-min glycogen-reducing exercise, and consumed a low CHO meal, prior to completing an overnight fast. A 1-h cycle time trial was performed the following morning. Four trials, each separated by 7 days, were conducted in a randomized, counterbalanced study design: 15% CHO mouth rinse (CHOR), 7.5% CHO ingestion (CHOI), placebo mouth rinse (PLAR) and placebo ingestion (PLAI). Solution volumes (1.5 ml · kg−1 ingestion trials and 0.33 ml · kg−1 rinsing trials) were provided after every 12.5% of completed exercise. Perceptual scales were used to assess affective valence (feeling scale, FS), arousal (felt arousal scale, FAS), exertion (ratings of perceived exertion, RPE) and mood (profile of mood states, POMS) before, during and immediately after exercise.ResultsThere was no difference in RPE (CHOI, 14.0 ± 1.9; CHOR, 14.2 ± 1.7; PLAI, 14.6 ± 1.8; PLAR, 14.6 ± 2.0; P = 0.35), FS (CHOI, 0.0 ± 1.7; CHOR, −0.2 ± 1.5; PLAI, −0.8 ± 1.4; PLAR, −0.8 ± 1.6; P = 0.15), or FAS (CHOI, 3.6 ± 1.1; CHOR, 3.5 ± 1.0; PLAI, 3.4 ± 1.4; PLAR, 3.3 ± 1.3; P = 0.725) scores between trials. While overall POMS score did not appear to differ between trials, the ‘vigour’ subscale indicated that CHOI may facilitate the maintenance of ‘vigour’ scores over time, in comparison to the steady decline witnessed in other trials (P = 0.04). There was no difference in time trial performance between trials (CHOI, 65.3 ± 4.8 min; CHOR, 68.4 ± 3.9 min; PLAI, 68.7 ± 5.3 min; PLAR, 68.3 ± 5.2 min; P = 0.21) but power output was higher in CHOI (231.0 ± 33.2 W) relative to other trials (221–223.6 W; P < 0.01).ConclusionsIn a CHO-reduced state, mouth rinsing with a CHO solution did not impact on perceptual responses during high-intensity exercise in trained cyclists and triathletes. On the other hand CHO ingestion improved perceived ratings of vigour and increased power output during exercise.

Carbohydrate mouth rinsing has no effect on power output during cycling in a glycogen-reduced state.

BackgroundThe effect of mouth rinsing with a carbohydrate (CHO) solution on exercise performance is inconclusive with no benefits observed in the fed state. This study examined the effect of CHO mouth rinse or CHO ingestion on performance in 9 moderately trained male cyclists.MethodsFour trials were undertaken, separated by 7 days, in a randomized, counterbalanced design. Each trial included a 90-min glycogen-reducing exercise protocol, immediately followed by a low CHO meal and subsequent overnight fast; the following morning a 1-h cycling time trial was conducted. The trials included 15 % CHO mouth rinse (CHOR), 7.5 % CHO ingestion (CHOI), placebo mouth rinse and placebo ingestion. Solutions were provided after every 12.5 % of completed exercise: 1.5 mL · kg−1 and 0.33 mL · kg−1 body mass during ingestion and rinse trials, respectively. During rinse trials participants swirled the solution for 8 s before expectorating. Blood samples were taken at regular intervals before and during exercise.ResultsPerformance time was not different between trials (P = 0.21) but the 4.5-5.2 % difference between CHOI and other trials showed moderate practical significance (Cohen’s d 0.57-0.65). Power output was higher in CHOI relative to other trials (P < 0.01). There were no differences between CHOR and placebo groups for any performance variables. Plasma glucose, insulin and lactate concentrations were higher in CHOI relative to other groups (P < 0.05).ConclusionsIn a fasted and glycogen-reduced state ingestion of a CHO solution during high-intensity exercise enhanced performance through stimulation of insulin-mediated glucose uptake. The CHO mouth rinsing had neither ergogenic effects nor changes in endocrine or metabolic responses relative to placebo.

Design of the Glucose Rate Increase Detector: A Meal Detection Module for the Health Monitoring System.

The Glucose Rate Increase Detector (GRID), a module of the Health Monitoring System (HMS), has been designed to operate in parallel to the glucose controller to detect meal events and safely trigger a meal bolus. The GRID algorithm was tuned on clinical data with 40-70 g CHO meals and tested on simulation data with 50-100 g CHO meals. Active closed- and open-loop protocols were executed in silico with various treatments, including automatic boluses based on a 75 g CHO meal and boluses based on simulated user input of meal size. An optional function was used to reduce the recommended bolus using recent insulin and glucose history. For closed-loop control of a 3-meal scenario (50, 75, and 100 g CHO), the GRID improved median time in the 80-180 mg/dL range by 17% and in the >180 range by 14% over unannounced meals, using an automatic bolus for a 75 g CHO meal at detection. Under open-loop control of a 75 g CHO meal, the GRID shifted the median glucose peak down by 73 mg/dL and earlier by 120 min and reduced the time >180 mg/dL by 57% over a missed-meal bolus scenario, using a full meal bolus at detection. The GRID improved closed-loop control in the presence of large meals, without increasing late postprandial hypoglycemia. Users of basal-bolus therapy could also benefit from GRID as a safety alert for missed meal corrections.

Alcohol Ingestion Impairs Maximal Post-Exercise Rates of Myofibrillar Protein Synthesis following a Single Bout of Concurrent Training

IntroductionThe culture in many team sports involves consumption of large amounts of alcohol after training/competition. The effect of such a practice on recovery processes underlying protein turnover in human skeletal muscle are unknown. We determined the effect of alcohol intake on rates of myofibrillar protein synthesis (MPS) following strenuous exercise with carbohydrate (CHO) or protein ingestion.MethodsIn a randomized cross-over design, 8 physically active males completed three experimental trials comprising resistance exercise (8×5 reps leg extension, 80% 1 repetition maximum) followed by continuous (30 min, 63% peak power output (PPO)) and high intensity interval (10×30 s, 110% PPO) cycling. Immediately, and 4 h post-exercise, subjects consumed either 500 mL of whey protein (25 g; PRO), alcohol (1.5 g·kg body mass−1, 12±2 standard drinks) co-ingested with protein (ALC-PRO), or an energy-matched quantity of carbohydrate also with alcohol (25 g maltodextrin; ALC-CHO). Subjects also consumed a CHO meal (1.5 g CHO·kg body mass−1) 2 h post-exercise. Muscle biopsies were taken at rest, 2 and 8 h post-exercise.ResultsBlood alcohol concentration was elevated above baseline with ALC-CHO and ALC-PRO throughout recovery (P<0.05). Phosphorylation of mTORSer2448 2 h after exercise was higher with PRO compared to ALC-PRO and ALC-CHO (P<0.05), while p70S6K phosphorylation was higher 2 h post-exercise with ALC-PRO and PRO compared to ALC-CHO (P<0.05). Rates of MPS increased above rest for all conditions (∼29–109%, P<0.05). However, compared to PRO, there was a hierarchical reduction in MPS with ALC-PRO (24%, P<0.05) and with ALC-CHO (37%, P<0.05).ConclusionWe provide novel data demonstrating that alcohol consumption reduces rates of MPS following a bout of concurrent exercise, even when co-ingested with protein. We conclude that alcohol ingestion suppresses the anabolic response in skeletal muscle and may therefore impair recovery and adaptation to training and/or subsequent performance.

Technosphere Insulin Effectively Controls Postprandial Glycemia in Patients with Type 2 Diabetes Mellitus

This pilot trial was designed to determine if an optimal dose of Technosphere(®) insulin (TI) inhalation powder (MannKind Corp., Valencia, CA) could be used regardless of variation in meal carbohydrate (CHO) content. In total, eight subjects (seven men, one woman) with type 2 diabetes were enrolled. Subjects underwent dose optimization meal challenge (MC) visits (100% CHO) and MCs with varied CHO meal contents (50%, 200%, and 0% calculated CHOs). Primary end point was change in postprandial glucose (PPG) excursions. Baseline demographics were 60±7 years of age, diabetes duration of 12.3±4.27 years, hemoglobin A1c (A1C) of 7.82±1.04%, and body mass index of 31.3±5.48 kg/m(2). Maximum mean PPG excursions for the nominal 100% CHO meals were -13±15 mg/dL for breakfast (B) and -14±15 mg/dL for lunch (L), similar to those after 50% CHO meals (B, -17±16 mg/dL; L, +14±10 mg/dL). The largest excursions occurred during 200% CHO meals and remained below American Diabetes Association targets (B, +19±16 mg/dL; L, +32±29 mg/dL). During 15 of the MCs, subjects took their usual TI dose and then had no meal (0% CHO). For the 0% CHO MCs, the largest mean PPG excursion were -33±9 mg/dL at 60 min (B) and -31±10 mg/dL at 60 and 90 min (L). Mean A1C dropped from 7.82±1.04% at the Week 1 visit to 6.18±0.46% (P=0.00091) at the Week 19 visit. Results in eight patients suggest that once an optimal dose of TI is determined, type 2 diabetes patients can ingest meals with a wide range of CHO content or even skip meals without severe hypoglycemia. During this pilot study TI therapy improved A1C by -1.63% (P=0.00091) during 19 weeks of treatment.

Effect of Fat and CHO Meals on Intermittent Exercise in Soccer Players

Pre-exercise meals containing carbohydrates (CHO) are recommended to athletes, although there is evidence to suggest that a high fat meal prior to exercise increases utilisation of fats yet may not adversely affect performance. This study investigated the effect of a high fat and high CHO pre-exercise meal prior to high intensity intermittent exercise. Ten male recreational soccer players performed a soccer specific protocol followed by a 1 km time trial 3 ½ h after ingesting one of 2 test meals, high fat meal (HFM) or a high CHO meal (HCM). Blood glucose, fatty acids (FA), glycerol, β-hydroxybutyrate, lactate and insulin were assessed prior to the meal, pre-exercise, half-time, and post-exercise, whilst rates of CHO and fat oxidation were determined at 4 time points during the exercise as well as heart rate (HR) and rating of perceived exertion (RPE). Significant increases in FA, glycerol, β-hydroxybutyrate and fat oxidation after the HFM were observed, while CHO oxidation was significantly higher following the HCM (P<0.05). No performance effect was found for the 1 km time trial (HFM: 228.6+14.4 s; HCM: 229.4+26.5 s) (mean+SD). These findings suggest that the type of meal ingested prior to soccer simulated exercise has an impact on metabolism, but not on the subsequent performance as determined in the present study.

Modeling the Effects of Subcutaneous Insulin Administration and Carbohydrate Consumption on Blood Glucose

Estimation of the magnitude and duration of effects of carbohydrate (CHO) and subcutaneously administered insulin on blood glucose (BG) is required for improved BG regulation in people with type 1 diabetes mellitus (T1DM). The goal of this study was to quantify these effects in people with T1DM using a novel protocol. The protocol duration was 8 hours: a 1-3 U subcutaneous (SC) insulin bolus was administered and a 25-g CHO meal was consumed, with these inputs separated by 3-5 hours. The DexCom SEVEN® PLUS continuous glucose monitor was used to obtain SC glucose measurements every 5 minutes and YSI 2300 Stat Plus was used to obtain intravenous glucose measurements every 15 minutes. The protocol was tested on 11 subjects at Sansum Diabetes Research Institute. The intersubject parameter coefficient of variation for the best identification method was 170%. The mean percentages of output variation explained by the bolus insulin and meal models were 68 and 69%, respectively, with root mean square error of 14 and 10 mg/dl, respectively. Relationships between the model parameters and clinical parameters were observed. Separation of insulin boluses and meals in time allowed unique identification of model parameters. The wide intersubject variation in parameters supports the notion that glucose-insulin models and thus insulin delivery algorithms for people with T1DM should be personalized. This experimental protocol could be used to refine estimates of the correction factor and the insulin-to-carbohydrate ratio used by people with T1DM.

Effect of Preexercise Glycemic-Index Meal on Running When CHO-Electrolyte Solution Is Consumed during Exercise

This study examined the effect of consuming carbohydrate- (CHO) electrolyte solution on running performance after different-glycemic-index (GI) meals. Nine men completed 3 trials in a randomized counterbalanced order, with trials separated by at least 7 days. Two hours before the run after an overnight fast, each participant consumed a high-GI (GI = 83) or low-GI (GI = 36) CHO meal or low-energy sugar-free Jell-O (GI = 0, control). The 2 isocaloric GI meals provided 1.5 g available CHO/kg body mass. During each trial, 2 ml/kg body mass of a 6.6% CHO-electrolyte solution was provided immediately before exercise and every 2.5 km after the start of running. Each trial consisted of a 21-km performance run on a level treadmill. The participants were required to run at 70% VO2max during the first 5 km of the run. They then completed the remaining 16 km as fast as possible. There was no difference in the time to complete the 21-km run (high-GI vs. low-GI vs. control: 91.1 +/- 2.0 vs. 91.8 +/- 2.2 vs. 92.9 +/- 2.0 min, n.s.). There were no differences in total CHO and fat oxidation throughout the trials, despite differences in preexercise blood glucose, serum insulin, and serum free-fatty-acid concentrations. When a CHO-electrolyte solution is consumed during a 21-km run, the GI of the preexercise CHO meal makes no difference in running performance.

The effect of a high fat and high carbohydrate meal on satiety hormone response and subjective hunger in humans

The effect of macronutrient content on postprandial hormonal release and subjective hunger was investigated in 10 male subjects. In random order, subjects either continued an overnight fast or were given a meal high in carbohydrate (CHO) or fat Blood samples and subjective hunger ratings were recorded 30 minutes preprandial and at 30, 90, and 210 minutes postprandial. Following the CHO meal, postprandial levels of insulin, C-peptide, and amylin were significantly greater (all: P<0.001) and GLP-1 had a non-significant increase when compared to fat. Following the fat meal, glucagon and GLP-1 increased significantly compared to the CHO meal (both: P<0.001). Whilst hormonal responses were different following the CHO and fat meal, postprandial subjective hunger ratings did not significantly differ. In both meal protocols, “fullness” was associated with plasma GLP-1 (r = 0.84, P<0.01), glucagon (r = −0.80, P<0.01), and C-peptide (r = −0.65, P<0.05). “Hunger” was related to GLP-1 (r = − 0.84, P<0.01) and C-peptide (r = 0.77, P<0.01), whereas “desire to eat” was solely correlated to GLP-1 (r = −0.85, P<0.01)). In conclusion, although a single meal high in CHO or fat produced differing postprandial hormonal responses, subjective hunger was not affected. It appears that there are varying degrees of hormonal action that can influence subjective hunger, suggesting that when different macronutrients are consumed distinct combinations of hormones are released. However, these varying hormonal combinations seem to affect subjective hunger similarly. Funded by AHFMR and CIHR.

Effect Of Increased Dosage Of Carbohydrate-electrolyte Ingestion During Intermittent Running Exercise On Soccer Skill Performance

In a previous study we gave subjects ∼30 g CHO.hour−1 and found trends towards a greater sustainability of soccer skill performance than when they ingested a colour matched placebo. PURPOSE The aim of this study was to examine the effect of ingesting a beverage delivering 45 g CHO.hour−1 during the Loughborough Intermittent Shuttle running Test (LIST) on soccer passing and shooting skill tests. METHODS Seventeen healthy male university soccer players ingested either a 6.4% CHO or placebo (PLA) solution during 90 min of the LIST (8 ml.kg BM−1 before and 3 ml.kg BM−1 every 15 min of exercise), in a double-blind randomised design, with each trial separated by at least 7 days. On the evening before the main trial, after a standardised warm up, subjects performed both skill tests (baseline), followed by a glycogen reduction (cycling) exercise. They were then fed a low CHO meal and reported to the laboratory the following morning after a 10 h fast. Both skill tests were performed before and after the 90- min LIST. Expired air was collected every 15 min during the LIST using the Douglas bag technique and venous blood samples were taken at rest and every 30 min of exercise. RESULTS The combined data showed that the passing test performance decreased by 7% from baseline to post-LIST (mean±SE, 40.5±0.9 to 43.5±1.2 s, P< 0.05). In the CHO trial there was a 4% decrease and a 14% decrease in the PLA trial but the difference between trials was not statistically significant (P = 0.07). There were no performance differences for the shooting test. The respiratory exchange ratio (RER) was significantly higher in the CHO trial throughout exercise (0.89±0.004 vs. 0.86±0.004, P< 0.05). Plasma glucose concentrations were higher in the CHO trial after 60 (5.4±0.2 vs. 4.6±0.2 mmol.l−1, P< 0.05) and 90 min (5.2±0.1 vs. 4.0±0.3 mmol.l−1, P< 0.01) of exercise. Plasma free fatty acid (FFA) concentrations were higher in the PLA trial after 60 (0.5±0.1 vs. 0.9±0.1 mmol.l−1, P< 0.05) and 90 min 0.6±0.1 vs. 1.1±0.2 mmol.l−1, P< 0.01) of exercise. CONCLUSIONS Ingesting CHO at 45 g.hour−1 led to an increased CHO oxidation during the LIST and a reduced reliance on FFA. However, the trends in maintenance of soccer skill performance were similar to our previous study thus suggesting there are no added benefits of consuming the extra CHO during soccer-type activity.

Effect Of Increased Dosage Of Carbohydrate-electrolyte Ingestion During Intermittent Running Exercise On Soccer Skill Performance

In a previous study we gave subjects ∼30 g CHO.hour−1 and found trends towards a greater sustainability of soccer skill performance than when they ingested a colour matched placebo. PURPOSE The aim of this study was to examine the effect of ingesting a beverage delivering 45 g CHO.hour−1 during the Loughborough Intermittent Shuttle running Test (LIST) on soccer passing and shooting skill tests. METHODS Seventeen healthy male university soccer players ingested either a 6.4% CHO or placebo (PLA) solution during 90 min of the LIST (8 ml.kg BM−1 before and 3 ml.kg BM−1 every 15 min of exercise), in a double-blind randomised design, with each trial separated by at least 7 days. On the evening before the main trial, after a standardised warm up, subjects performed both skill tests (baseline), followed by a glycogen reduction (cycling) exercise. They were then fed a low CHO meal and reported to the laboratory the following morning after a 10 h fast. Both skill tests were performed before and after the 90- min LIST. Expired air was collected every 15 min during the LIST using the Douglas bag technique and venous blood samples were taken at rest and every 30 min of exercise. RESULTS The combined data showed that the passing test performance decreased by 7% from baseline to post-LIST (mean±SE, 40.5±0.9 to 43.5±1.2 s, P< 0.05). In the CHO trial there was a 4% decrease and a 14% decrease in the PLA trial but the difference between trials was not statistically significant (P = 0.07). There were no performance differences for the shooting test. The respiratory exchange ratio (RER) was significantly higher in the CHO trial throughout exercise (0.89±0.004 vs. 0.86±0.004, P< 0.05). Plasma glucose concentrations were higher in the CHO trial after 60 (5.4±0.2 vs. 4.6±0.2 mmol.l−1, P< 0.05) and 90 min (5.2±0.1 vs. 4.0±0.3 mmol.l−1, P< 0.01) of exercise. Plasma free fatty acid (FFA) concentrations were higher in the PLA trial after 60 (0.5±0.1 vs. 0.9±0.1 mmol.l−1, P< 0.05) and 90 min 0.6±0.1 vs. 1.1±0.2 mmol.l−1, P< 0.01) of exercise. CONCLUSIONS Ingesting CHO at 45 g.hour−1 led to an increased CHO oxidation during the LIST and a reduced reliance on FFA. However, the trends in maintenance of soccer skill performance were similar to our previous study thus suggesting there are no added benefits of consuming the extra CHO during soccer-type activity.

Effect of short-term fasting and refeeding on transcriptional regulation of metabolic genes in human skeletal muscle.

During short-term fasting, substrate utilization in skeletal muscle shifts from predominantly carbohydrate to fat as a means of conserving glucose. To examine the potential influence of short-term fasting and refeeding on transcriptional regulation in skeletal muscle, muscle biopsies were obtained from nine male subjects at rest, after 20 h of fasting, and 1 h after consuming either a high-carbohydrate (CHO trial) or a low-carbohydrate (FAT trial) meal. Fasting induced an increase in transcription of the pyruvate dehydrogenase kinase 4 (PDK4) (10-fold), lipoprotein lipase (LPL) ( approximately 2-fold), uncoupling protein 3 (UCP3) ( approximately 5-fold), and carnitine palmitoyltransferase I (CPT I) ( approximately 2.5-fold) genes. Surprisingly, transcription of PDK4 and LPL increased further in response to refeeding (both trials) to more than 50-fold and 6- to 10-fold, respectively, over prefasting levels. However, responses varied among subjects with two subjects in particular displaying far greater activation of PDK4 (>100-fold) and LPL (>20-fold) than the other subjects (mean approximately 8-fold and approximately 2-fold, respectively). Transcription of UCP3 decreased to basal levels after the CHO meal but remained elevated after the FAT meal, whereas CPT I remained elevated after both refeeding meals. The present findings demonstrate that short-term fasting/refeeding in humans alters the transcription of several genes in skeletal muscle related to lipid metabolism. Marked heterogeneity in the transcriptional response to the fasting/refeeding protocol suggests that individual differences in genetic profile may play an important role in adaptive molecular responses to metabolic challenges.

Effects of Training Status on the Metabolic Responses to High Carbohydrate and High Fat Meals

The purpose of this study was to determine if there is a difference between the way in which aerobically trained and untrained women metabolize fats and carbohydrates at rest in response to either a high-fat or high-carbohydrate meal. Subjects, 6 per group, were fed a high CHO meal (2068 kJ, 76% CHO, 23% fat, 5% protein) and a high fat meal (2093 kJ, 21% CHO, 72% fat, 8% protein) in counterbalanced order. Resting metabolic rate (RMR) was measured every half-hour for 5 hours. RMR was similar between groups. However, after ingesting a high CHO meal, trained subjects had a peak in metabolism at minute 60, not evident in the untrained subjects. In addition, postprandial RER from minutes 120-300 were lower and fat use was greater after the high CHO meal for the trained subjects. These results suggest that aerobically trained women have an accelerated CHO uptake and overall lower CHO oxidation following the ingestion of a high CHO meal.

Preexercise medium-chain triglyceride ingestion does not alter muscle glycogen use during exercise

This investigation determined whether ingestion of a tolerable amount of medium-chain triglycerides (MCT; approximately 25 g) reduces the rate of muscle glycogen use during high-intensity exercise. On two occasions, seven well-trained men cycled for 30 min at 84% maximal O(2) uptake. Exactly 1 h before exercise, they ingested either 1) carbohydrate (CHO; 0.72 g sucrose/kg) or 2) MCT+CHO [0.36 g tricaprin (C10:0)/kg plus 0.72 g sucrose/kg]. The change in glycogen concentration was measured in biopsies taken from the vastus lateralis before and after exercise. Additionally, glycogen oxidation was calculated as the difference between total carbohydrate oxidation and the rate of glucose disappearance from plasma (R(d) glucose), as measured by stable isotope dilution techniques. The change in muscle glycogen concentration was not different during MCT+CHO and CHO (42.0 +/- 4.6 vs. 38.8 +/- 4.0 micromol glucosyl units/g wet wt). Furthermore, calculated glycogen oxidation was also similar (331 +/- 18 vs. 329 +/- 15 micromol. kg(-1). min(-1)). The coingestion of MCT+CHO did increase (P < 0.05) R(d) glucose at rest compared with CHO (26.9 +/- 1.5 vs. 20.7 +/- 0. 7 micromol.kg(-1). min(-1)), yet during exercise R(d) glucose was not different during the two trials. Therefore, the addition of a small amount of MCT to a preexercise CHO meal did not reduce muscle glycogen oxidation during high-intensity exercise, but it did increase glucose uptake at rest.

CARBOHYDRATE AVAILABILITY DETERMINES ENDURANCE RUNNING CAPACITY IN FASTED SUBJECTS

299 We studied the influence of different amounts of pre-exercise carbohydrate (CHO) and fat on metabolism and endurance running capacity. On three occasions, six endurance-trained runners ran at 71%VO2max to exhaustion (EXH) on a level treadmill. Three hours before exercise, in a single-blind and randomized manner, subjects consumed either a high CHO-low fat meal (CM), a high fat-low CHO meal (FM) or a high CHO-high fat meal (HM). The meals contained the following amounts of energy, CHO, fat and protein respectively per 70 kg bodyweight: FM: 756 kcal, 70g, 49g 8g; CM: 759 kcal, 175g, 3g, 8g; HM: 1173 kcal, 175g, 49g, 8g. Endurance run time was 14% less following the FM than CM and HM (P<0.01). At the onset of exercise, serum insulin concentrations during the FM trial had returned to fasting values and were lower than in the CM (P<0.1) and HM (P<0.05) trials. Plasma glucagon concentrations were higher 60 min into exercise and at EXH during the FM than the CM and HM (P<0.05) trials. Plasma FFA and glycerol concentrations were highest during exercise in FM (P<0.05 from CM and HM) trial and lowest in the CM (P<0.05 from HM) trial. During the first 80 min of exercise in the FM trial, total CHO oxidation was 19% and 14% lower than during the CM and HM trials respectively (P<0.01). We conclude that CHO rather than fat availability before exercise exerts predominant control over substrate selection during exercise and determines endurance running capacity.

The effect of an eucaloric high carbohydrate diet on circulating levels of glucose, fructose and non-esterified fatty acids in patients with cirrhosis

Twelve cirrhotic patients and six controls were fed an eucaloric high carbohydrate (CHO) diet for 3 days. Fasting serum triglyceride (TG), non-esterified fatty acids (NEFA), glucose, insulin and glycerol were estimated daily. On the 3rd day of the study we measured NEFA, glucose, insulin, and fructose every 45 min from 07:45 h until 19:45 h, and then every 4 h until 07:45 h the next day. The patients were divided into two groups of six on the basis of plasma lecithin-cholesterol acyltransferase (LCAT) activity: group A cirrhotics (with good liver function--LCAT activity: 40.6-65.7 nmol.ml-1.h-1; mean 48.5), and group B (poor liver function--LCAT: 23.7-32.3; mean 27.4). On the high CHO diet there was an increase in the fasting serum TG with a peak after 2 or 3 days. The increase in serum TG in controls was greater (p less than 0.01) than in either group of cirrhotics. In the controls and in group A most of the extra TG was carried in VLDL; in group B only 39% of the TG increment was found in VLDL. Fasting NEFA fell with 3 days of CHO feeding in the control group (p less than 0.01); they were unchanged in group A, and rose in group B to a significantly higher level than in controls (p less than 0.01). During day 3 when a high CHO diet was fed plasma NEFA levels fell in cirrhotics, and for most of the day the mean NEFA concentration in group B patients was significantly (p less than 0.05) lower than in normals. On day 3 glucose and fructose levels rose after each meal--much more in cirrhotics than in controls (and more in group B than in group A), and for most of the day they were significantly higher in group B patients as compared to the controls (glucose p less than 0.01, fructose p less than 0.001). Our results supported the hypothesis that plasma NEFA would be lower following high CHO meals in cirrhotics than in controls. This suggests that a high NEFA utilisation, which occurs in fasting cirrhotics, is not present throughout the day. Following a CHO meal, we suggest that tissues derive energy directly from the dietary sugars which are present in high concentration during the period of absorption and that this reduces the post prandial requirement for NEFA.

&amp;beta;-Endorphin and Insulin/Glucose Responses to Different Meals in Obesity

The responses of plasma beta-endorphin, insulin and glucose to two different isocaloric mixed meals--high carbohydrate (CHO meal) and high fat (fat meal)--were assessed in women with android obesity before (n = 11) as well as after (n = 5) weight reduction, and in normal-weight controls (n = 8). Basal plasma beta-endorphin concentrations in the obese subjects (7.7 +/- 1.2 pmol/l) were significantly (p less than 0.005) higher than in the controls (3.8 +/- 0.5 pmol/l) and were not influenced by weight loss. Fasting plasma levels and the integrated releases of insulin and glucose, both after the CHO meal and after the fat meal were significantly higher in the obese subjects than in the controls. The fat meal induced no changes in beta-endorphin levels in either group. After the CHO meal a significant decrease in plasma beta-endorphin concentration was observed only in the obese group before weight reduction. An influence on beta-endorphin release by macronutrients is hypothesized.