Metabolic responses to high glycemic index and low glycemic index meals: a controlled crossover clinical trial (original) (raw)
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British Journal of …, 2003
The present study was designed to examine the effects of mixed high-carbohydrate meals with different glycaemic indices (GI) on substrate utilization during subsequent exercise. Nine healthy male recreational runners (age 26•8 (SEM 1•1) years, body mass 74•7 (SEM 2•4) kg, V O 2 max 58•1 (SEM 1•7) ml/kg per min) completed three trials: high-glycaemic-index meal (HGI), low-glycaemic-index meal (LGI) and fasting (FAST), separated by 7 d. The test meals contained 2 g carbohydrate/kg body mass, they were isoenergetic and the GI values were 77•4, 36•9 and 0•0 respectively. In each trial, subjects consumed the test meal 3 h before performing a 60 min run at 65 % V O 2 max on a motorized treadmill. Ingestion of the HGI and LGI resulted in hyperglycaemia and hyperinsulinaemia during the postprandial period compared with the FAST (P, 0•05). The incremental area under the curve for plasma glucose was 2-fold higher for HGI compared with LGI (108•7 v. 48•9 mmol/l per min). In contrast, plasma non-esterified fatty acid concentrations were significantly lower following HGI and LGI compared with FAST (P, 0•05). During the subsequent submaximal exercise, plasma glucose declined to below the fasting value in HGI compared with LGI and FAST (P, 0•05). The estimated total fat oxidation was significantly higher for the LGI than the HGI during exercise (P,0•05). In summary, both pre-exercise carbohydrate meals resulted in lower rates of fat oxidation during subsequent exercise than when subjects performed exercise in the fasting state. However, the LGI resulted in a higher rate of fat oxidation during exercise than following the consumption of the HGI.
British Journal of Nutrition, 2005
The present study investigated the effects of mixed high-carbohydrate (CHO) meals (breakfast and lunch) with different glycaemic indices (GI) on substrate metabolism during rest throughout the postprandial periods and during subsequent exercise. Nine recreationally active males completed two trials, high glycaemic index (HGI) and low glycaemic index (LGI), separated by 7 d in a randomised crossover design. In each trial, participants consumed breakfast and lunch, both of which were followed by a 3 h resting postprandial period. Following this, participants completed a 60 min run at 70 % of _ VO 2max . The plasma glucose and serum insulin concentrations following both meals were significantly higher in the HGI trial than in the LGI trial (P,0·05). Serum insulin concentrations remained higher throughout the postprandial period following lunch in the HGI trial compared with the LGI trial (P,0·05). The total amount of fat oxidised was higher during the 3 h rest following lunch in the LGI trial than in the HGI trial (P,0·01) and subsequently CHO oxidation was lower (P,0·005). No significant differences in substrate utilisation were observed throughout the subsequent run. At 45 and 60 min, plasma glucose concentrations were higher in the LGI trial v. the HGI trial (P,0·05). The results of the present study provide further support that the GI concept can be successfully applied to mixed meals. The results also suggest that meals composed of LGI CHO may be more beneficial for maintaining a favourable metabolic milieu during the postprandial periods. Furthermore, during subsequent exercise, plasma glucose concentrations were better maintained following the LGI CHO meals.
American Journal of Clinical Nutrition
Background: Few data exist on the metabolic responses to mixed meals with different glycemic indexes and their effects on substrate metabolism during exercise in women. Objective: We examined the effects of preexercise mixed meals providing carbohydrates with high (HGI) or low glycemic index (LGI) on substrate utilization during rest and exercise in women. Design: Eight healthy, active, eumenorrheic women [aged 18.6 Ȁ 0.9 y; body mass: 59.9 Ȁ 7.1 kg; maximal oxygen uptake (V O 2 max): 48.7 Ȁ 1.1 mL · kg Ҁ1 · min Ҁ1 ] completed 2 trials. On each occasion, subjects were provided with a test breakfast 3 h before performing a 60-min run at 65% V O 2 max on a motorized treadmill. Both breakfasts provided 2 g carbohydrate/kg body mass and were isoenergetic. The calculated GIs of the meals were 78 (HGI) and 44 (LGI). Results: Peak plasma glucose and serum insulin concentrations were greater after the HGI breakfast than after the LGI breakfast (P 0.05). No significant differences in substrate oxidation were reported throughout the postprandial period. During exercise, the estimated rate of fat oxidation was greater in the LGI trial than in the HGI trial (P 0.05). Similarly, plasma free fatty acid and glycerol concentrations were higher throughout exercise in the LGI trial (P 0.05). No significant differences in plasma glucose or serum insulin were observed during exercise. Conclusion: Altering the GI of the carbohydrate within a meal significantly changes the postprandial hyperglycemic and hyperinsulinemic responses in women. A LGI preexercise meal resulted in a higher rate of fat oxidation during exercise than did an HGI meal.
British Journal of Nutrition, 2012
The metabolic and performance benefits of prior consumption of low-glycaemic index (GI) meals v. high-GI meals were determined in extended high-intensity intermittent exercise. Participants (ten males and four females, aged 25·8 (SD 7·3) years) completed two testing days (each consisting of back-to-back 90-min intermittent high-intensity treadmill running protocols separated by 3 h) spaced by at least 7 d. Using a randomised counterbalanced cross-over design, low-GI, lentil-based meals (GI about 42) or high-GI, potato-based meals (GI about 78) matched for energy value were consumed 2 h before, and within 1 h after, the first exercise session. Performance was measured by the distance covered during five 1-min sprints (separated by 2·5 min walking) at the end of each exercise session. Peak postprandial blood glucose was higher by 30·8 % in the high-GI trial compared with the low-GI trial, as was insulin (P¼ 0·039 and P¼ 0·003, respectively). Carbohydrate oxidation was lower by 5·5 % during the low-GI trials compared with the high-GI trials at the start of the first exercise session (P, 0·05). Blood lactate was significantly higher (6·1 v. 2·6 mmol/l; P¼0·019) and blood glucose significantly lower (4·8 v. 5·4 mmol/l; P¼0·039) at the end of the second exercise session during the high-GI trial compared with the low-GI trial. Sprint distance was not significantly different between conditions. A low-GI meal improved the metabolic profile before and during extended high-intensity intermittent exercise, but did not affect performance. Improvements in metabolic responses when consuming low-GI meals before exercise may be beneficial to the long-term health of athletes.
Metabolic response to different glycemic indexes of pre-exercise meal
Revista Brasileira de Medicina do Esporte, 2015
INTRODUCTION: To ensure performance and health, the type of food and the time of pre-exercise ingestion should be considered by practitioners of morning physical activity. Objective: This study assessed the metabolic response after pre-exercise meals with different glycemic indexes (GI) and in the fasting state adopting different types of hydration.METHODS: Twelve men performed four experimental tests; two with pre-exercise meals of high GI (HGI) and low GI (LGI), and two were performed in the fasting state with hydration: water (H2O) and carbohydrate drink (CHO). Each test consisted of a pre-exercise rest period of 30 minutes followed by 60 minutes of cycle ergometer with continuous load equivalent to 60% of the extrapolated maximal oxygen consumption (VO2MaxExt). During the exercise, participants were hydrated every 15 minutes with 3mL per kg body weight. During each experimental test, venous blood samples were obtained for fasting and at 15-minute intervals during rest, and every...
Journal of Science and Medicine in Sport, 2010
This study investigated the effects of low or high glycaemic index (GI) foods consumed prior to a 40 km time trial (TT) on metabolism and subsequent endurance performance. Ten male cyclists consumed high GI or low GI meals, providing 1 g kg −1 body mass of carbohydrate, 45 min prior to the TT. The TT performance was significantly (p = 0.009) improved in the low (93 ± 8 min) compared to the high GI trial (96 ± 7 min). Low GI carbohydrate oxidation rate (2.51 ± 1.71 g min −1 ) was higher (p = 0.003) than the HGI carbohydrate oxidation rate (2.14 ± 1.5 g min −1 ). Fat oxidation rate was significantly higher (p = 0.002) for the high (0.27 ± 0.17 g min −1 ) than the low GI trial (0.16 ± 0.14 g min −1 ). Insulin rose significantly following the high compared to the low GI meal (p = 0.008) but dropped significantly to similar values throughout the TT. No significant differences in either TGA or FFA concentration were observed between the trials. The low GI meal led to an increase in the availability of carbohydrate and a greater carbohydrate oxidation throughout the exercise period, which may have sustained energy production towards the end of exercise and led to the improved TT performance observed.
European Journal of Clinical Nutrition
To investigate whether the 'overnight second-meal effect' results in altered substrate oxidation during the postprandial period following breakfast and subsequent sub-maximal exercise in women. Seven recreationally active women were recruited for the study. In each trial, participants were provided with their evening meal on day 1, which was composed of either high glycaemic index (HGI) or low glycaemic index (LGI) carbohydrates (CHO). On day 2, participants were provided with a standard HGI breakfast and then performed a 60 min run at 65% \[V.]O(2 max) 3 h later. The incremental area under the curve (IAUC) for plasma glucose concentrations during the postprandial period following breakfast was greater in the HGI trial compared to the LGI trial (P<0.01). Similarly, the IAUC for serum insulin concentrations was greater in the HGI trial than the LGI trial (P<0.05). No differences in plasma free-fatty acids (FFA) or plasma glycerol concentrations were found between trials...
Effects of a moderate glycemic meal on exercise duration and substrate utilization
Medicine & Science in Sports & Exercise, 2001
of a moderate glycemic meal on exercise duration and substrate utilization. Med. Sci. Sports Exerc., Vol. 33, No. 9, 2001, pp. 1517-1523. Purpose: To determine whether eating a breakfast cereal with a moderate glycemic index could alter substrate utilization and improve exercise duration. Methods: Six active women (age, 24 Ϯ 2 yr; weight, 62.2 Ϯ 2.6 kg; V O 2peak , 46.6 Ϯ 3.8 mL·kg Ϫ1 ·min Ϫ1 ) ate 75 g of available carbohydrate in the form of regular whole grain rolled oats (RO) mixed with 300 mL of water or water alone (CON). The trials were performed in random order and the meal or water was ingested 45 min before performing cycling exercise to exhaustion (60% of V O 2peak ). Blood samples were drawn for glucose, glucose kinetics, free fatty acids (FFA), glycerol, insulin, epinephrine (EPI), and norepinephrine (NE) determination. A muscle biopsy was obtained from the vastus lateralis muscle before the trial and immediately after exercise for glycogen determination. Glucose kinetics (Ra) were determined using a [6,6-2 H] glucose tracer. Results: Compared with CON, plasma FFA and glycerol levels were suppressed (P Ͻ 0.05) during the first 120 min of exercise for the RO trial. Respiratory exchange ratios (RER) were also higher (P Ͻ 0.05) for the first 120 min of exercise for the RO trial. At exhaustion, glucose, insulin, FFA, glycerol, EPI, NE, RER, and muscle glycogen were not different between trials. Glucose Ra was greater (P Ͻ 0.05) during the RO trial compared with CON (2.36 Ϯ 0.22 and 1.92 Ϯ 0.27 mg·kg· Ϫ1 min Ϫ1 , respectively). Exercise duration was 5% longer during RO, but the mean times were not significantly different (253.6 Ϯ 6 and 242.0 Ϯ 15 min, respectively). Conclusions: Increased hepatic glucose output before fatigue provides some evidence of glucose sparing after the breakfast cereal trial. However, exercise duration was not significantly altered, possibly because of the sustained suppression of lipid metabolism and increased carbohydrate utilization throughout much of the exercise period.