High Glycaemic Index Breakfast Research Articles

Relevance of high glycaemic index breakfast for heart rate variability among collegiate students with early and late chronotypes

ABSTRACT Plasma glucose spikes affect cardiac autonomic modulation resulting in a decrease of heart rate variability (HRV). We hypothesize that a later chronotype or a higher morning plasma melatonin level is associated with larger decreases of HRV following an early high glycaemic index (GI) breakfast. In persons with an early (n = 21) or a late (n = 15) chronotype who consumed a high GI breakfast at 7 a.m. glucose data were continuously monitored. Time domain HRV parameters were calculated from blood volume pulses derived by wireless wrist worn multisensor. HRV changes (values after minus values before breakfast) were associated with chronotype by multivariable linear regression adjusted for age, sex and baseline levels. Morning plasma melatonin levels were determined from samples drawn on the run-in day. Time domain parameters indicate a higher HRV before high GI breakfast in both chronotypes. A later chronotype tended to be associated with smaller decreases of mean interbeat intervals (p = 0.08) only; no associations were seen with morning melatonin levels. This exploratory analysis in a small sample provides a first indication that in young healthy adults later chronotype might be associated with reduced ANS activation following a high GI breakfast. Future studies should elucidate whether this indicates parasympathetic or sympathetic inhibition.

Breakfast consumption modulates postprandial glycaemic, insulinaemic and NEFA response in pre-diabetic Asian males.

Breakfast consumption is associated with a variety of nutritional and lifestyle-related health outcomes. The objective of the present study was to investigate how the consumption of breakfast affected blood glucose, insulin and NEFA profiles. A lower postprandial blood glucose, insulin and NEFA response is associated with a lower risk of development of metabolic diseases. In a randomised crossover non-blind design, thirteen pre-diabetic Chinese adult males (BMI 26·7 (sd 4·2) kg/m2) attended two sessions where they either consumed a high-glycaemic index breakfast or no breakfast consumption. Changes in glycaemic response over 27 h periods were measured using the Medtronic MiniMed iProTM2 continuous glucose monitoring system. Blood samples were collected using a peripheral venous catheter at fixed intervals for 3 h after the test meal and 3 h after standardised lunch consumption. Postprandial glucose, insulin and NEFA response was calculated as total AUC and incremental AUC using the trapezoidal rule that ignored the area under the baseline. It was found that breakfast consumption significantly decreased postprandial glucose, insulin and NEFA excursion response at lunch time (P = 0·001). Consumption of breakfast attenuated blood glucose profiles by minimising glycaemic excursions and reduced both insulinaemic and NEFA responses in pre-diabetic Asian males during the second meal. This simple dietary intervention may be a novel approach to help improve subsequent lunch glycaemic responses in Asians at high risk of developing diabetes.

Lowering breakfast glycemic index and glycemic load attenuates postprandial glycemic response: A systematically searched meta-analysis of randomized controlled trials

Low glycemic index (GI) diets are recommended to reduce the risk for chronic diseases by managing postprandial elevations in blood glucose and insulin. However, to our knowledge, a systematic review of randomized controlled trials (RCTs) to investigate this relationship and interpret its clinical relevance has yet to be performed. This review aims to assess the effect of low versus high GI breakfast meals on postprandial glycemic and insulinemic responses in adults. Two researchers independently screened 1100 articles from PubMed, CINAHL, Medline, and Cochrane databases and extracted data from 11 qualified RCTs. Meta-analyses were performed to calculate overall effect sizes of postintervention blood glucose concentration change values at different time points (60, 90, and 120 min) using a random-effects model, reporting their weighted mean differences (WMDs) and 95% confidence intervals (CIs). Low GI breakfasts significantly reduced postprandial blood glucose concentrations at all time points: 60 min (WMD: -1.32 mmol/L; 95% CIs, -1.64 to -0.99), 90 min (WMD: -0.74 mmol/L; 95% CI, -0.92 to -0.56), and 120 min (WMD: -0.44 mmol/L; 95% CI, -0.63 to -0.26). Further analyses not only indicated similar trends following the stratification of studies according to the glycemic load, but also showed a more pronounced decline in glycemic response among individuals with metabolic impairments. These results highlight the benefits of lowering breakfast meal GI to provide clinically relevant reductions in acute glucose response.

The Effect of Added Peanut Butter on the Glycemic Response to a High–Glycemic Index Meal: A Pilot Study

Objective: The purpose of this pilot study was to determine whether supplementation of a high–glycemic index breakfast meal with peanut butter attenuates the glycemic response.Methods: Sixteen healthy adults, aged 24.1 ± 3.5 years, reported in the morning to a nutrition assessment laboratory for two days of data collection, having fasted 8 to 12 hours. On day 1 (control), fasting blood glucose (BG) was measured using glucometers, then participants consumed two slices of white bread and 250 mL apple juice (60 g carbohydrate) within 15 minutes. BG was measured again at 15, 30, 60, 90, and 120 minutes after the first bite of the meal. On day 2, the protocol was repeated, except 32 g (2 tbsp) of peanut butter was added to the meal (treatment).Results: The spike in BG was significantly lower on the treatment versus control day (35.8 ± 16.4 vs. 51.0 ± 20.8 mg/dL, respectively; p < 0.01), and BG was significantly lower on the treatment day at 15, 30, and 60 minutes post–meal consumption (p < 0.05).Conclusions: This study indicates that supplementation with 32 g (2 tbsp) peanut butter attenuates the magnitude of BG spike and overall glycemic response to high–glycemic index meal and may be a practical, beneficial strategy to prevent undesirable elevations in BG.

Postprandial effects of breakfast glycaemic index on cognitive performance among young, healthy adults: A crossover clinical trial

Objective: To evaluate the postprandial effects of high and low glycaemic index (GI) breakfasts on cognitive performance in young, healthy adults.Methods: A crossover clinical trial including 40 young, healthy adults (aged 20–40 years, 50% females) recruited from primary healthcare centres in Salamanca, Spain. Verbal memory, phonological fluency, attention, and executive functions were examined 0, 60, and 120 minutes after consuming a low GI (LGI), high GI (HGI), or water breakfast. Every subject tried each breakfast variant, in a randomized order, separated by a washout period of 7 days, for a total of 3 weeks.Results: A significant interaction between the type of breakfast consumed and immediate verbal memory was identified (P<.05). We observed a trend towards better performance in verbal memory (delayed and immediate), attention, and phonological fluency following an LGI breakfast.Discussion: Cognitive performance during the postprandial phase in young, healthy adults was minimally affected by the GI of breakfast. The potential for breakfast’s GI modulation to improve short- and long-term cognitive functioning requires further research.

Postprandial Effects of Breakfast Glycemic Index on Vascular Function among Young Healthy Adults: A Crossover Clinical Trial

This study aimed to evaluate the postprandial effects of high and low glycemic index (GI) breakfasts on vascular function. It was a crossover trial that included 40 young healthy adults (50% women), aged 20–40 years, who were recruited at primary care settings. They consumed three experimental breakfasts in randomized order, each one separated by a 1-week washout period: (1) control conditions (only water); (2) low GI (LGI) breakfast (29.4 GI and 1489 KJ energy); and (3) high GI (HGI) breakfast (64.0 GI and 1318 KJ energy). Blood samples were collected at 60 and 120 min after each breakfast to determine glucose and insulin levels. Vascular parameters were measured at 15 min intervals. Augmentation index (AIx) was studied as a primary outcome. Secondary outcomes comprised glucose, insulin, heart rate (HR) and pulse pressures (PPs). We found a trend toward increased AIx, HR and PPs for the HGI versus the LGI breakfast. A significant interaction between the type of breakfast consumed and all measured parameters was identified (p < 0.05) except for central PP. Stratifying data by sex, this interaction remained significant for AIx and augmentation pressure only in males (p < 0.05). In conclusion, breakfast GI could affect postprandial vascular responses in young healthy adults.

Effects of breaking up prolonged sitting following low and high glycaemic index breakfast consumption on glucose and insulin concentrations

PurposeBreaking up prolonged sitting can attenuate the postprandial rise in glucose and insulin. Whether such effects are dependent of the glycaemic index (GI) of the consumed carbohydrate is unknown. This study examined the acute effects of breaking up prolonged sitting following a low GI and a high GI breakfast on postprandial glucose and insulin concentrations.ProceduresFourteen adult males aged 22.1 ± 1.2 years completed four, 4 h experimental conditions: high GI breakfast followed by uninterrupted sitting (HGI-SIT), low GI breakfast followed by uninterrupted sitting (LGI-SIT), high GI breakfast followed by 2 min activity breaks every 20 min (HGI-ACT), and low GI breakfast followed by 2 min activity breaks every 20 min (LGI-ACT). Positive incremental area under the curve (iAUC) for glucose and insulin (mean [95% CI]) for each 4 h experimental condition was calculated. Statistical analyses were completed using linear mixed models.ResultsThe sitting × breakfast GI interaction was not significant for glucose positive iAUC (P = 0.119). Glucose positive iAUC (mmol/L 4 h−1) was significantly lower in the activity breaks conditions than the uninterrupted sitting conditions (2.07 [2.24, 2.89] vs. 2.56 [1.74, 2.40], respectively, P = 0.004) and significantly lower in the low GI conditions than the high GI conditions (2.13 [1.80, 2.45] vs. 2.51 [2.18, 2.84], respectively, P = 0.022). Insulin concentrations did not differ between conditions (P ≥ 0.203).ConclusionsBreaking up prolonged sitting and lowering breakfast GI independently reduced postprandial glucose responses. This indicates that interrupting prolonged sitting and reducing dietary GI are beneficial approaches for reducing cardiometabolic disease risk.

Effect of high and low glycemic index breakfast on postprandial metabolic parameters and satiety in subjects with type 2 diabetes mellitus under intensive insulin therapy: Controlled clinical trial

The results of studies evaluating the metabolic effects of glycemic index (GI) in subjects with type 2 diabetes mellitus (DM2) have been contradictory. Consequently, the benefits of its application are controversial and polarized opinions of international organizations have been disclosed. The above situation leads this study to evaluate the acute effect of low and high GI breakfast on the glycemic response and satiety in subjects with DM2 under intensive insulin therapy (IIT). A controlled, crossover and single-blind clinical trial was developed involving 10 obese subjects with DM2 under IIT, with a period of at least six months under IIT and with fast insulin prescription before breakfast. Subjects ingested on two different occasions a high or low GI breakfast. In both stages, glycemia was evaluated at 0 (basal), 30, 60 and 120min, and satiety and satiation were evaluated through a visual analogue scale. In contrast to high GI breakfast, the low GI meal generated a significant decrease of 46% for the area under the curve of glucose (Δ 1940mg/dL×120min, p=0.022) and in mean glycemia evaluated at 30, 60 and 120min. Moreover, in the low GI stage 8 of 10 patients achieved a 2h postprandial glycemia lower than 180mg/dL, without statistical significance. A nonsignificant increase of 12.7% (Δ 1.06cm, p=0.271) in satiety at 120min in the low GI stage was observed. In contrast to high GI breakfast, the low GI breakfast generated a significantly lower glycemic response. This assay allowed for the contribution of more in depth nutritional recommendations for this group of patients. Registered under ClinicalTrials.gov Identifier no. NCT02881164.

Sex differences in adolescents' glycaemic and insulinaemic responses to high and low glycaemic index breakfasts: a randomised control trial.

During puberty young people undergo significant hormonal changes which affect metabolism and, subsequently, health. Evidence suggests there is a period of transient pubertal insulin resistance, with this effect greater in girls than boys. However, the response to everyday high and low glycaemic index (GI) meals remains unknown. Following ethical approval, forty adolescents consumed a high GI or low GI breakfast, in a randomised cross-over design. Capillary blood samples were taken during a 2-h postprandial period, examining the glycaemic and insulinaemic responses. Maturity offset and homoeostatic model assessment (HOMA) were also calculated. The glycaemic response to the breakfasts was similar between boys and girls, as shown by similar peak blood glucose concentrations and incremental AUC (IAUC) following both high and low GI breakfasts (all P>0·05). Girls exhibited a higher peak plasma insulin concentration 30 min post-breakfast following both high GI (P=0·043, g=0·69) and low GI (P=0·010, g=0·84) breakfasts, as well as a greater IAUC following high GI (P=0·041, g=0·66) and low GI (P=0·041, g=0·66) breakfasts. HOMA was positively correlated with the insulinaemic responses (all P<0·0005) and maturity offset (P=0·037). The findings of the present study suggest that pubertal insulin resistance affects the postprandial insulinaemic responses to both high and low GI meals. Specifically, girls exhibit a greater insulinaemic response than boys to both meals, despite similar glycaemic responses. This study is the first to report the glycaemic and insulinaemic responses to everyday meals in boys and girls, supporting the recommendation for young people to base their diet on low GI carbohydrates.

Postprandial effect of breakfast glycaemic index on vascular function, glycaemic control and cognitive performance (BGI study): study protocol for a randomised crossover trial.

BackgroundPostprandial glycaemic response affects cognitive and vascular function. The acute effect of breakfast glycaemic index on vascular parameters is not sufficiently known. Also, the influence of breakfasts with different glycaemic index on cognitive performance has been mostly studied in children and adolescents with varying results. Therefore, the purpose of this study is to analyse the postprandial effect of high and low glycaemic index breakfasts on vascular function and cognitive performance and their relationship with postprandial glycaemic response in healthy young adults.Methods/designThis is a crossover clinical trial targeting adults (aged 20–40 years, free from cardiovascular disease) selected by consecutive sampling at urban primary care health clinics in Salamanca (Spain). Each subject will complete three interventions with a washout period of one week: a control condition (consisting of water); a low glycaemic index breakfast (consisting of dark chocolate, walnuts, yogurt and an apple, with an overall glycaemic index of 29.4 and an energy contribution of 1489 kJ); and a high glycaemic index breakfast (consisting of bread, grape juice and strawberry jam, with an overall glycaemic index of 64.0 and an energy contribution of 1318 kJ). The postprandial effect will be assessed at 60 and 120 minutes from each breakfast including blood sampling and cognitive performance evaluations. Measurements of arterial stiffness and central haemodynamic parameters will be taken at –10, 0, 15, 30, 45, 60, 75, 90, 105 and 120 minutes.DiscussionThe differences in postprandial glycaemic response due to breakfast glycaemic index could affect vascular parameters and cognitive performance with important applications and implications for the general population. This could provide necessary information for the establishment of new strategies in terms of nutritional education and work performance improvement.Trial registrationClinicalTrials.gov: NCT02616276. Registered on 19 November 2015.Electronic supplementary materialThe online version of this article (doi:10.1186/s13063-016-1649-x) contains supplementary material, which is available to authorized users.

The impact of a low glycemic index (GI) breakfast and snack on daily blood glucose profiles and food intake in young Chinese adult males

ObjectiveLow glycemic index (GI) foods have been suggested to minimize large fluctuations in blood glucose levels and reduce food intake. However, the majority of studies have been conducted on Caucasian populations with limited data on Asians. The objective of this study was to investigate how the provision of a low GI breakfast and afternoon snack affected daily blood glucose profiles and food intake. Materials and methodsIn a randomized, controlled crossover non blind design, 11 healthy Chinese male adults (body mass index 22.4 ± 1.3 kg m−2) attended two sessions where they consumed either a high or low GI breakfast and afternoon snack, and a standardized buffet lunch. Daily changes in glycemic response (GR) were measured using the Medtronic MiniMed (Northridge, CA) iPro™2 continuous glucose monitoring system (CGMS). The GR was further calculated to obtain the incremental area under the curve (IAUC). Glycemic variability was calculated as mean amplitude of glycemic excursion (MAGE) and energy intake (kcal) was measured quantitatively at the buffet lunch. ResultsCompared to the high GI intervention, the low GI intervention significantly reduced the GR following breakfast (p = 0.02), lunch (p = 0.02) and dinner (p = 0.05). The low GI treatment showed a reduction in daily AUC (p = 0.03). There was a significant reduction in IAUC after a low GI breakfast compared to the high GI breakfast (p = 0.03). The low GI breakfast resulted in a significantly lower food intake at lunch and a resulting decreased energy intake of 285 kcal (p = 0.02). The MAGE was significantly lower during the entire low GI treatment (p = 0.03). ConclusionsConsumption of a low GI breakfast and afternoon snack was capable of attenuating 24-h blood glucose profiles, minimize glycemic excursions and reduce food intake in healthy Asian males. This simple dietary intervention may be an acceptable approach in improving overall glycemia and energy balance in Asians. Clinical trial registration numberNCT02340507

OC96: An investigation into the effect of a low versus high glycaemic index breakfast on satiety and subsequent food intake.

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Breakfast glycaemic index and exercise: Combined effects on adolescents' cognition

The aim of the present study was to examine the combined effects of breakfast glycaemic index (GI) and a mid-morning bout of exercise on adolescents' cognitive function.Participants were randomly allocated to a high or low GI breakfast group in a mixed research design, where each participant completed two experimental trials (exercise and resting). Forty-two adolescents (12.4±0.5years old), undertook a bout of exercise (ten repeats of level one of the multi-stage fitness test; exercise trial) or continued to rest (resting trial) following consumption of either a high or low GI breakfast. A battery of cognitive function tests (visual search test, Stroop test and Sternberg paradigm) was completed 30min before and 45min following the exercise.Average heart rate during exercise was 170±15beats·min−1. On the complex level of the Stroop test, response times improved across the morning following the low GI breakfast on both the exercise and resting trials, though the improvement was greatest on the exercise trial. However, response times only improved on the resting trial following the high GI breakfast (p=0.012). On the 5 letter level of the Sternberg paradigm, response times improved across the morning following the low GI breakfast (regardless of exercise) and only on the exercise trial following the high GI breakfast (p=0.019).The findings of the present study suggest that the combined effects of breakfast GI and exercise in adolescents depend upon the component of cognitive function examined. A low GI breakfast and mid-morning bout of exercise were individually beneficial for response times on the Sternberg paradigm, whereas they conferred additional benefits for response times on the Stroop test.

Further evidence for a second meal cognitive effect. Evening meal glycaemic index manipulations are associated with cognitive performance in the evening and the next day

Consumption of low glycaemic index (GI) foods at breakfast has been associated with cognitive benefits over the morning. However, the effects of evening meal GI manipulations on cognitive performance remain unexplored. The aims of the research were to investigate cognitive performance in the evening, and to replicate a previous finding that the GI of an evening meal is associated with cognitive performance the next morning following a standard breakfast, even after an overnight fast. Twenty-three healthy adults (16 females, 7 males) mean age 21.5 years (s.d. 2.4) consumed high GI (GI 83) and low GI (GI 28) evening meals matched for energy and macronutrients in a counterbalanced order following a cross-over, single-blind design. Memory, psychomotor skill and executive function were assessed 45 min post evening meal consumption and the next morning 15 min post consumption of a high GI breakfast (GI 88). Improved memory performance in the evening was associated with the low GI evening meal, whereas, improved memory performance the next day was associated with the high GI evening meal. This indicates that the cognitive effects of GI manipulations may differ in the acute postprandial phase relative to longer postprandial periods such as following a subsequent meal. Moreover, these findings provide further evidence for a second meal cognitive effect, indicating that an overnight fast may not be sufficient to control for any confounding effects of previous nutritional intake.

Timing of Peak Blood Glucose after Breakfast Meals of Different Glycemic Index in Women with Gestational Diabetes

This study aims to determine the peak timing of postprandial blood glucose level (PBGL) of two breakfasts with different glycemic index (GI) in gestational diabetes mellitus (GDM). Ten women with diet-controlled GDM who were between 30 and 32 weeks of gestation were enrolled in the study. They consumed two carbohydrate controlled, macronutrient matched bread-based breakfasts with different GI (low vs. high) on two separate occasions in a random order after an overnight fast. PBGLs were assessed using a portable blood analyser. Subjects were asked to indicate their satiety rating at each blood sample collection. Overall the consumption of a high GI breakfast resulted in a greater rise in PBGL (mean ± SEM peak PBGL: low GI 6.7 ± 0.3 mmol/L vs. high GI 8.6 ± 0.3 mmol/L; p < 0.001) and an earlier peak PBGL time (16.9 ± 4.9 min earlier; p = 0.015), with high variability in PBGL time between subjects. There was no significant difference in subjective satiety throughout the test period. In conclusion, the low GI breakfast produced lower postprandial glycemia, and the peak PBGL occurred closer to the time recommended for PBGL monitoring (i.e., 1 h postprandial) in GDM than a macronutrient matched high GI breakfast.

Colonic fermentation of indigestible carbohydrates of a previous evening meal increases tissue glucose uptake

Evening meals rich in indigestible carbohydrates have been shown to lower postprandial glucose concentrations after ingestion of a high glycemic index breakfast. This phenomenon is linked to colonic fermentation of indigestible carbohydrates but the underlying mechanism is not fully elucidated. We examined in which way glucose kinetics after the breakfast are changed due to colonic fermentation. In a cross‐over manner 10 healthy male subjects (21 ± 2 years, BMI: 21,4 ± 1 kg/m2) ingested as an evening meal either white wheat bread or cooked barley kernels, rich in indigestible carbohydrates. In the morning the dual isotope technique was applied to determine glucose kinetics after intake of 50 g 13C‐enriched glucose. Plasma insulin and non‐esterified fatty acid concentrations were measured as well as hydrogen excretion in breath. Postprandial glucose response was 29 % lower after the barley evening meal, whereas the concentrations of insulin and non‐esterified fatty acids were the same. Exogenous glucose appearance in the systemic circulation and endogenous glucose production did not differ, but tissue glucose uptake was increased after the barley evening meal. Hydrogen excretion was higher after the barley meal indicating increased colonic fermentation. Factors related to colonic fermentation of indigestible carbohydrate seem to have the ability to increase tissue insulin sensitivity in healthy subjects.

The impact of a high versus a low glycaemic index breakfast cereal meal on verbal episodic memory in healthy adolescents

In this study, healthy adolescents consumed either (i) a low glycaemic index breakfast cereal meal or (ii) a high glycaemic index breakfast cereal meal, before completing a test of verbal episodic memory in which the memory materials were encoded under conditions of divided attention. Analysis of remembering/forgetting indices revealed that the high glycaemic index breakfast group remembered significantly more items relative to the low glycaemic index breakfast group after a long delay. The superior performance observed in the high glycaemic index group, relative to the low glycaemic index group, may be due to the additional glucose availability provided by the high glycaemic index meal at the time of memory encoding. This increased glucose availability may be necessary for effective encoding under dual task conditions.

The influence of the glycaemic index of an evening meal on the glycaemic response to breakfast and subsequent cognitive performance in young adults

It has been reported that the glycaemic response to consumption of a high glycaemic index (GI) breakfast is higher after consuming a high GI evening meal compared to a low GI evening meal. However, no research has investigated how this ‘previous meal effect’ may influence cognitive performance. Eight young, healthy, male participants consumed a low GI and a high GI evening meal, in a counterbalanced order. In each condition, the following morning a high GI breakfast was consumed. Immediate recall, delayed recall, recognition, and attention were assessed before and after breakfast, and blood glucose was measured throughout. The blood glucose profiles following each meal were not significantly different between the high and low GI meals. However, there was an association between evening and morning glycaemic responses, with higher evening glycaemic responses being associated with higher morning glycaemic responses. Generally, there were no associations between GI and cognitive performance or between morning glycaemic response and cognitive performance. In conclusion, the glycaemic response to an evening meal can influence the glycaemic response to breakfast. This has implications for research investigating any associations between blood glucose, nutritional manipulations, and cognitive performance.

Influence of the glycaemic index of an evening meal on substrate oxidation following breakfast and during exercise the next day in healthy women

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 during the postprandial period. During subsequent exercise, there were no significant differences in substrate metabolism. The glycaemic index of an evening meal does not alter substrate oxidation at rest following breakfast or during subsequent submaximal exercise in women. This study provides further evidence for the overnight second-meal effect on glycaemic responses following a LGI mixed evening meal.

Effects of the glycemic index of breakfast on metabolic responses to brisk walking in females

The aim of this study was to examine the metabolic responses during 1 h of brisk walking, 3 h after ingesting high glycemic index (HGI) and moderate glycemic index (MGI) breakfasts. Six females completed three treadmill walking trials (approximately 50% VO2 max), separated by at least 1 month. Three hours before walking, they ingested either water or a HGI or MGI breakfast. The MGI breakfast consisted of a mixture of an HGI breakfast cereal and low GI carbohydrate (CHO) foods. The GI values of the HGI and MGI meals were 77 and 51, respectively. The study took place in the School of Sport and Exercise Sciences at Loughborough University, Loughborough, UK. In the HGI and MGI trials, plasma glucose and serum insulin concentrations peaked 15 min into the postprandial period. At the onset of exercise, plasma insulin concentrations were twofold higher in the HGI (31.5+/-7.7 microl U l(-1)) than in the MGI trial (15.2+/-1.9 microl U l(-1)) (P<0.05). However, there were no differences in substrate utilization between the two CHO trials. These results suggest that although the addition of LGI CHO foods to an HGI breakfast cereal reduces the overall GI of the meal, the metabolic response to exercise is similar to that following a breakfast comprised entirely of HGI foods.