high-GI Meal Research Articles

The Effect of Meal Glycemic Index and Meal Frequency on Glycemic Control and Variability in Female Nurses Working Night Shifts: A Two-Arm Randomized Cross-Over Trial

BackgroundNight shift workers are exposed to circadian disruption, which contributes to impaired glucose tolerance. Although fasting during the night shift improves glucose homeostasis, adhering to this dietary strategy may be challenging. ObjectivesThis study evaluated the effect of fasting compared with the consumption of meals with different combinations of glycemic index (GI, low or high) and frequency (1 or 3 times) during the night shift on continuous glucose monitoring metrics. MethodsA 2-arm randomized cross-over trial was conducted on female nurses working night shifts. In each of those arms, the participants were either provided with no meal (fasted), low GI, or high-GI meal during the night shift with a meal frequency according to which arm they were randomly allocated to, either 1-MEAL or 3-MEAL. Outcome variables were glycemic control and variability (GC and GV) metrics during the night shift (21:30–7:00), in the morning after the night shift (07:00–13:00), and in the 24 h period (18:00–18:00). ResultsCompared to no meal, the consumption of 1 high-GI meal increased all GV metrics not only during the night shifts but also in the morning, for instance, as observed in the coefficient of variation (β = 0.03 mmol/L; 95% CI: 0.01, 0.05), and GV percentage (β = 4.13; 95% CI: 2.07, 6.18). The consumption of 1 or 3 low GI meals did not raise GC or GV metrics except for continuous overall net glycemic action during the night shifts after consuming 3 low GI meals. When controlling for GI, night shift meal frequency did not affect any metrics in any timeframe. ConclusionsHigh meal GI but not higher meal frequency during the night shift increased GC and GV in female night shift workers. Results for 1 low-GI meal during the night shift were not different from a glucose profile after no meal.This trial was registered at trialsearch.who.int as NL8715.

Glycemic index and insulin index after a standard carbohydrate meal consumed with live kombucha: A randomised, placebo-controlled, crossover trial.

Kombucha is a complex probiotic beverage made from fermented tea, yet despite extensive historical, anecdotal, and in-vivo evidence for its health benefits, no controlled trials have been published on its effect on humans. We conducted a randomised placebo-controlled, cross-over study that examined the Glycemic Index (GI) and Insulin Index (II) responses after a standardised high-GI meal consumed with three different test beverages (soda water, diet lemonade soft drink and an unpasteurised kombucha) in 11 healthy adults. The study was prospectively registered with the Australian New Zealand Clinical Trials Registry (anzctr.org.au: 12620000460909). Soda water was used as the control beverage. GI or II values were calculated by expressing the 2-h blood glucose or insulin response as a percentage of the response produced by 50 g of glucose dissolved in water. There was no statistically significant difference in GI or II between the standard meal consumed with soda water (GI: 86 and II: 85) or diet soft drink (GI: 84 and II: 81, (p = 0.929 for GI and p = 0.374 for II). In contrast, when kombucha was consumed there was a clinically significant reduction in GI and II (GI: 68, p = 0.041 and II: 70, p = 0.041) compared to the meal consumed with soda water. These results suggest live kombucha can produce reductions in acute postprandial hyperglycemia. Further studies examining the mechanisms and potential therapeutic benefits of kombucha are warranted.

GLYCEMIC RESPONSE OF FOUR BREAD TYPES CONSUMED BY HEALTHY SUBJECTS IN BENIN CITY, NIGERIA

The glycemic response of four types of Bread commonly eaten in Benin City, Nigeriawere analysed in healthy individuals. Proximate analyses of the bread samples weredetermined; to get the amount that would give 50g carbohydrate. Fifty male subjectswere fed the different varieties of bread respectively. Control subjects were given50g glucose solution. Blood glucose concentrations were determined at 0mins(before feeding), 15, 30, 45, 60, 90 and 120 mins (after feeding). The glycemicindices varied from 34.13±2.98 (Sample A: Whole wheat bread) to 78.18±2.69(Sample D: Coconut bread). Whole wheat bread is a low GI meal while Coconutbread is a high GI meal

Changes in peripheral inflammation-related gene expression by postprandial glycemic response in healthy Japanese men

ObjectivesContinuous postprandial hyperglycemia is associated with the onset of cardiovascular disease. In recent years, the mRNA expression of inflammation-related genes in peripheral blood leukocytes has been shown to be induced by an increase in blood glucose levels. The aim of this study was to investigate differences in the expression of inflammation-related genes in peripheral blood leukocytes in response to an increase in blood glucose from individuals who consumed two kinds of breakfast meals with different glycemic indexes (GIs). MethodsTwenty healthy Japanese men 40 to 70 y of age were given low- or high-GI meals for breakfast for 14 d. Clinical examinations were performed on days 7 and 14. Their blood glucose levels and insulin concentrations were measured from before breakfast ingestion to 120 min after. Additionally, using the blood obtained before and 120 min after breakfast, the mRNA expression levels of inflammation-related genes in peripheral leukocytes were measured. ResultsThe blood glucose levels were significantly lower in the low-GI meal intake group at 30, 60, and 120 min after breakfast than in the high-GI meal intake group. The intake of high-GI meals for 6 d led to an increase in the mRNA levels of interleukin-1β, S100A4, and CD18 compared with the period of low-GI meals. ConclusionThe intake of a low-GI breakfast for 1 wk in healthy Japanese men resulted in lower postprandial blood glucose and insulin levels, which were accompanied by a reduced expression of inflammation-related genes in peripheral blood leukocytes.

721-P: Fat Added to High-Glycemic–Index Foods Reduces Both Glycemic and Insulinemic Response to Moderate-Size Meals

Fat has been shown to be a powerful modifier of dietary glycemic response (Flint et al 2004). But other research shows addition of fat to high GI meals worsens insulinemic response (Gannon et al 1993). The author hypothesized that researched insulin response was more related to excessive meal size (50+ gms of both carbohydrate and fat) than to fat content per se. The current study compared starch or sugar based nonfat 50 gm carb meals (∼250 kcal) with meals containing 30 gm amounts of both fat and carb (∼450 kcal) in 12 healthy 21-75 year old volunteers (6-8 per subgroup) without glucose intolerance. Size of subgroups was similar to that used in establishing the glycemic index (Jenkins et al 1981). Each subject served as their own control. Despite the larger meal size, the balanced carb/fat meals had lower glycemic and insulin responses, with p values of 0.009 and 0.016 for glycemic response, and 0.014 and 0.0275 for insulin response to starch and sugar-based meals, respectively (Wilcoxson, one tailed). Post-study interviews also demonstrated that subjects preferred the balanced meals. This pilot study has demonstrated that adding fat to moderate sized meals lowered, not raised, insulin levels, even when compared to much smaller nonfat meals. It also confirms previous research that fat lowers glycemic response and improves palatability. Taken together, these findings support further research into the potential benefit of balanced carb/fat meal combinations. Such meals might improve diet sustainability as well as efficacy. Future research can explore other fat types/amounts, and evaluate the utility of this concept in real world dietary management. Disclosure D.K. Jass: None.

Consuming decaffeinated coffee with milk and sugar added before a high-glycaemic index meal improves postprandial glycaemic and insulinaemic responses in healthy adults.

The present study aimed to compare the effects of drinking different types of coffee before a high-glycaemic index (GI) meal on postprandial glucose metabolism and to assess the effects of adding milk and sugar into coffee. In this randomised, crossover, acute feeding study, apparently healthy adults (n 21) consumed the test drink followed by a high-GI meal in each session. Different types of coffee (espresso, instant, boiled and decaffeinated, all with milk and sugar) and plain water were tested in separate sessions, while a subset of the participants (n 10) completed extra sessions using black coffees. Postprandial levels of glucose, insulin, active glucagon-like peptide 1 (GLP-1) and nitrotyrosine between different test drinks were compared using linear mixed models. Results showed that only preloading decaffeinated coffee with milk and sugar led to significantly lower glucose incremental AUC (iAUC; 14 % lower, P = 0·001) than water. Preloading black coffees led to greater postprandial glucose iAUC than preloading coffees with milk and sugar added (12-35 % smaller, P < 0·05 for all coffee types). Active GLP-1 and nitrotyrosine levels were not significantly different between test drinks. To conclude, preloading decaffeinated coffee with milk and sugar led to a blunted postprandial glycaemic response after a subsequent high-GI meal, while adding milk and sugar into coffee could mitigate the impairment effect of black coffee towards postprandial glucose responses. These findings may partly explain the positive effects of coffee consumption on glucose metabolism.

Nutrition Trial on the Glycaemic Response to High GI Meals Consumed at Morning vs. Evening-The ChroNu Study

Nutrition Trial on the Glycaemic Response to High GI Meals Consumed at Morning vs. Evening-The ChroNu Study

Glycemic Index, Extended Bolusing, and Diabetes Education in Insulin Pump Therapy (GLIDE: A Pilot Study)

Background: There is no published evidence on whether advanced bolus education affects outcomes in insulin pump-treated type 1 diabetes. We assess the feasibility of delivering a clinical education program on rates of digestion and bolusing, and to assess its preliminary impact. Methods: An interactive education session on glycemic index (GI), extended bolusing, and superbolusing was developed and assessed in a nonrandomized single-arm study for 12 weeks. Insulin pump-treated participants with type 1 diabetes were recruited. Glucose outcomes were assessed by blinded continuous glucose monitoring after the consumption of high-fat and high-GI test meal. The primary outcome measure was 8-h glucose area under the curve (AUC) after high-fat meals, before and after intervention. Secondary outcomes included time spent in hypoglycemia, quality of life, treatment satisfaction, HbA1c, frequency of use of extended boluses, and postprandial AUC. Results: Eleven participants completed the study [mean (SD) age 42.3 (12.8) years, baseline HbA1c 57.3 (10.0) mmol/mol, duration of diabetes 19.5 (9.9) years]. AUC for glucose after test meals did not differ significantly after education except for in the first 2 h after the high-GI meal [precourse 83.1 (0.23-88.9), postcourse 5.38 (-16.2 to 50.8)]. Percentage time spent in hypoglycemia (<3.9 and <3.3 mmol/L) fell at week 12 compared with baseline [5.8 (IQR 2.1-8.3) % to 4.3 (IQR 2.1-5.4) %, P = 0.013, and 2.9 (IQR 1.2-3.9) % to 1.6 (IQR 0.7-2.4) %, P = 0.029, respectively]. Conclusion: Delivering an education program to support advanced boluses is feasible and may reduce exposure to hypoglycemia. A further trial is required to confirm the findings.

Glucose Control Using a Standard vs. an Enhanced Hybrid Closed-Loop System—A Pilot Study

Background: Hybrid closed loop (HCL) insulin delivery with the Medtronic MiniMed 670G system is safe and effective in improving glycemia for people with type 1 diabetes (T1D). Aims: To compare glucose control, CL exits and alarm frequency with standard HCL vs. enhanced HCL (eHCL) systems. Methods: Pump experienced adults with T1D (n=11; 9 women; mean[SD] age: 51[15]Y; HbA1c 7.5[1.0]%) were assigned in random order HCL and eHCL for 1 week each in a supervised live-in setting. eHCL incorporated enhanced bolus reminders and iterative changes broadening glucose and insulin delivery parameters permitting persistence in CL. For both HCL and eHCL insulin delivery was by a Medtronic pump with identical interventions (missed bolus, exercise, high GI and high fat meals), insulin action times and insulin-carbohydrate ratios implemented. The primary outcome was CGM time in target range. Results: eHCL resulted in fewer CL alerts and exits. Time in target and mean glucose favored eHCL but did not reach significance (Table). No episodes of severe hypoglycemia or ketoacidosis occurred. Conclusions: Iterative changes to the Medtronic HCL system resulted in trends towards improved glycemia, fewer CL exits and alerts without compromising safety, despite multiple food and exercise challenges during the study periods. Longer term studies at home are required to confirm these findings. Table: All results are Mean (SD); *NS= Not Significant.HCL (n=11)eHCL (n=11)pInsulin DeliveryTotal daily insulin (units/day)44 (18)47 (24)NS*Daily basal (%)55 (8)55 (7)NS*Daily bolus (%)45 (8)45 (7)NS*Daily insulin to carbohydrate ratio9.6 (3.1)9.6 (3.1)NS*Insulin action time (hrs)3.7 (0.6)3.7 (0.6)NS*Glucose Metrics% time in 70-180mg/dL69 (11)74 (10)0.16Mean sensor glucose (mg/dL)160 (13)151 (11)0.091Time &amp;lt;70mg/dL (%)1.9 (2.4)1.2 (1.2)0.42Time &amp;lt;50mg/dL (%)0.4 (0.5)0.2 (0.3)0.21Time&amp;gt;180mg/dL (%)29 (11)24 (9)0.37Time &amp;gt;250mg/dL (%)7.3 (5.6)6.1 (4.7)0.48Algorithm related Alerts and Dropout Alerts (n/week)8.6 (5.8)3.9 (2.8)0.01CL exits (n/week)3.5 (3.1)0 (0)0.004 Disclosure B. Paldus: None. M.H. Lee: None. H. Jones: None. S.A. McAuley: Research Support; Self; JDRF. Speaker's Bureau; Self; Novo Nordisk Inc., Australian Diabetes Society. J.C. Horsburgh: None. K.L. Roem: None. G. Ward: None. R. MacIsaac: None. N. Cohen: None. P.G. Colman: None. A. Jenkins: Research Support; Self; Medtronic, Mylan, Sanofi-Aventis. D.N. O'Neal: Research Support; Self; Medtronic MiniMed, Inc.. Advisory Panel; Self; Medtronic MiniMed, Inc.. Speaker's Bureau; Self; Medtronic MiniMed, Inc.. Advisory Panel; Self; Abbott. Speaker's Bureau; Self; Novo Nordisk Inc.. Advisory Panel; Self; Novo Nordisk Inc.. Research Support; Self; Novo Nordisk Inc.. Advisory Panel; Self; Sanofi. Research Support; Self; Sanofi.

Dietary fat and carbohydrate quality have independent effects on postprandial glucose and lipid responses.

The magnitude of postprandial lipemia is influenced not only by the amount but also the type of fat and carbohydrate consumed. The aim of this study was to evaluate differences in postprandial glucose and lipid responses after a mixed meal containing low- or high-glycemic-index (GI) carbohydrate and three different types of fat varying in the degree of saturation in healthy subjects. A randomized, controlled, single-blinded crossover study was conducted in 20 healthy Chinese men. Subjects consumed in random order six experimental isocaloric meals that differed in carbohydrate and fat quality, and contained 40g of either saturated fat (SFA, butter), monounsaturated fat (MUFA, olive oil) or polyunsaturated fat (PUFA, grapeseed oil), and 50g of either low-GI (basmati rice) or high-GI (jasmine rice) carbohydrate. Glucose, insulin, c-peptide, triglycerides (TG) and non-esterified fatty acids (NEFA) were measured over 4h. For all substrates evaluated, there were no significant interactions between fat and carbohydrate. The incremental area under the curve (iAUC) for TG was significantly lower after the SFA and PUFA meals compared with the MUFA meal, irrespective of GI. No significant difference was found for NEFA iAUC in all treatments. Glucose, insulin and c-peptide iAUCs were significantly lower after ingestion of low-GI than high-GI meals, independent of the type of fat. A carbohydrate-rich meal (of either low or high GI) that contains butter or grapeseed oil results in lower postprandial TG concentrations relative to olive oil in healthy Chinese males. Glucose, insulin and c-peptide responses, however, are directly dependent on the GI of the meal and not on the degree of saturation of dietary fat. The trial was registered at clinicaltrials.gov as NCT02585427.

Effect of Glycemic Index of Breakfast on Energy Intake at Subsequent Meal among Healthy People: A Meta-Analysis.

Meals with low glycemic index (GI) may suppress short-term appetite and reduce subsequent food intake compared with high-GI meals. However, no meta-analysis has been conducted to synthesize the evidence. This meta-analytic study was conducted to assess the effect of high- and low-GI breakfast on subsequent short-term food intake. Trials were identified through MEDLINE, EMBASE, Web of Science, and Cochrane Central Register of Controlled trials, and manual searches of bibliographies until May 2015. Randomized controlled and cross-over trials comparing the effect of low- with high-GI breakfast on subsequent energy intake among healthy people were included. Nine studies consisting of 11 trials met the inclusion criteria. Only one trial was classified with high methodological quality. A total of 183 participants were involved in the trials. The meta-analytic results revealed no difference in breakfast GI (high-GI vs. low-GI) on subsequent short-term energy intake. In conclusion, it seems that breakfast GI has no effect on short-term energy intake among healthy people. However, high quality studies are still warranted to provide more concrete evidence.

Effects of dietary glycemic index on brain regions related to reward and craving in men

Qualitative aspects of diet influence eating behavior, but the physiologic mechanisms for these calorie-independent effects remain speculative. We examined effects of the glycemic index (GI) on brain activity in the late postprandial period after a typical intermeal interval. With the use of a randomized, blinded, crossover design, 12 overweight or obese men aged 18-35 y consumed high- and low-GI meals controlled for calories, macronutrients, and palatability on 2 occasions. The primary outcome was cerebral blood flow as a measure of resting brain activity, which was assessed by using arterial spin-labeling functional magnetic resonance imaging 4 h after test meals. We hypothesized that brain activity would be greater after the high-GI meal in prespecified regions involved in eating behavior, reward, and craving. Incremental venous plasma glucose (2-h area under the curve) was 2.4-fold greater after the high- than the low-GI meal (P = 0.0001). Plasma glucose was lower (mean ± SE: 4.7 ± 0.14 compared with 5.3 ± 0.16 mmol/L; P = 0.005) and reported hunger was greater (P = 0.04) 4 h after the high- than the low-GI meal. At this time, the high-GI meal elicited greater brain activity centered in the right nucleus accumbens (a prespecified area; P = 0.0006 with adjustment for multiple comparisons) that spread to other areas of the right striatum and to the olfactory area. Compared with an isocaloric low-GI meal, a high-GI meal decreased plasma glucose, increased hunger, and selectively stimulated brain regions associated with reward and craving in the late postprandial period, which is a time with special significance to eating behavior at the next meal. This trial was registered at clinicaltrials.gov as NCT01064778.

Glycaemic index of meals affects appetite sensation but not energy balance in active males

Foods with low glycaemic index (LGI) are reported to suppress appetite mainly in overweight population but have not been investigated in athletic adults. The aim of this study was to compare the short-term effects of LGI and high GI (HGI) meals over a day on subsequent subjective appetite sensation, energy intake, energy expenditure, energy balance and resting metabolic rate in physically active males. This cross-sectional randomized crossover study included 14 active males (mean ± SD; age 34.5 ± 8.9 years, body mass index 22.8 ± 2.1 kg m(-2)) to consume LGI and HGI meals on two separate days. On each trial day, participants consumed a breakfast in the laboratory and then left with a packed lunch, dinner and snacks. Appetite scores, energy intake and expenditure were assessed. The area under the curve for appetite scores of the HGI trial was significantly smaller than that of the LGI trial during the laboratory period (p = 0.027) and throughout the day (p = 0.009). No significant differences in energy intake, energy expenditure, energy balance and resting metabolic rate were found between groups, between the trial days and between the corresponding post-trial days. These results show that frequent ingestion of the HGI meals, contrary to the previous reports, suppresses appetite more than that of LGI meals, but did not affect energy balance in physically active normal-weight males.

Metabolism and performance during extended high-intensity intermittent exercise after consumption of low- and high-glycaemic index pre-exercise meals

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 (P = 0·039 and P = 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; P = 0·019) and blood glucose significantly lower (4·8 v. 5·4 mmol/l; P = 0·039) 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.

INTERACTION BETWEEN DIETARY PHOSPHATE AND CARBOHYDRATE ON GLUCOSE AND PHOSPHATE METABOLISMS IN HEALTHY YOUNG MEN.

Interaction between the nutrients should be considered to understand the relationship between nutrient intake and disease. Here, we investigated the effects of combination of dietary phosphate and carbohydrate (glycemic index; GI) on urinary phosphate excretion, serum glucose, insulin, phosphate, PTH levels after the digestion of experimental meal in 11 young healthy men. We employed 4 different meals; high GI and high phosphate (HGHP), high GI and low phosphate (HGLP), low GI and high phosphate (LGHP), and low GI and low phosphate (LGLP). Barley was used for staple food in low GI meals, inversely white rice in high GI meals. Low phosphate meals contained 400 mg of phosphate, high phosphate meals contained 1200 mg of phosphate added as sodium phosphate. This study was performed as a crossover study, and approved by the ethical committee of the University of Tokushima. Ingestion of HGHP meal revealed higher postprandial phosphate excretion than LGHP meal. This difference was not observed between HGLP and LGLP meals. HGHP meals was also involved in higher postprandial increases in blood glucose and insulin than HGLP. Meanwhile intact PTH level in the ingestion of LGHP meals was significantly higher than that in HGHP. No significant difference in serum phosphate level between HGHP and LGHP groups. These data indicate that interaction between dietary phosphate and carbohydrate affected postprandial changes in serum glucose and phosphate handling in healthy young men.

Effect of meal timing and glycaemic index on glucose control and insulin secretion in healthy volunteers

Shiftworkers have a higher risk of CHD and type 2 diabetes. They consume a large proportion of their daily energy and carbohydrate intake in the late evening or night-time, a factor which could be linked to their increase in disease risk. We compared the metabolic effects of varying both dietary glycaemic index (GI) and the time at which most daily energy intake was consumed. We hypothesised that glucose control would be optimal with a low-GI diet, consumed predominantly early in the day. A total of six healthy lean volunteers consumed isoenergetic meals on four occasions, comprising either high- or low-GI foods, with 60 % energy consumed predominantly early (breakfast) or late (supper). Interstitial glucose was measured continuously for 20 h. Insulin, TAG and non-esterified fatty acids were measured for 2 h following every meal. Highest glucose values were observed when large 5021 kJ (1200 kcal) high-GI suppers were consumed. Glucose levels were also significantly higher in predominantly late high- v. low-GI meals (P<0·01). Using an estimate of postprandial insulin sensitivity throughout the day, we demonstrate that this follows the same trend, with insulin sensitivity being significantly worse in high energy consumed in the evening meal pattern. Both meal timing and GI affected glucose tolerance and insulin secretion. Avoidance of large, high-GI meals in the evening may be particularly beneficial in improving postprandial glucose profiles and may play a role in reducing the risk of type 2 diabetes; however, longer-term studies are needed to confirm this.

Substrate utilization during brisk walking is affected by glycemic index and fructose content of a pre-exercise meal

The purpose of the present study was to investigate whether both glycemic index (GI) and fructose content of a pre-exercise meal would affect substrate utilization during subsequent brisk walking. Ten healthy young males completed 60 min of 46% [Formula: see text] brisk walking 2 h after they consumed one of three breakfasts: a low-GI meal without fructose (LGI), a low-GI meal including fructose (LGIF), and a high-GI meal without fructose (HGI). The calculated GI values for the three meals were 41, 39, and 72, respectively. Substrate utilization was measured using indirect respiratory calorimetry method. During the postprandial period, the incremental area under the blood response curve values of glucose and insulin were higher in the HGI trial, compared with those in the LGI and LGIF trials (HGI vs. LGI and LGIF: Glucose 223.6 ± 19.1 vs. 70.2 ± 7.4 and 114.1 ± 16.4 mmol min L(-1); Insulin 4257 ± 932 vs. 920 ± 319 and 1487 ± 348 mU min L(-1)). During exercise, substrate preference was distinct based on different pre-exercise carbohydrate meals. Higher fat and lower carbohydrate oxidation was observed in the LGI trial, whereas both the HGI and LGIF trials were characterized by higher carbohydrate and lower fat oxidation (LGI vs. LGIF and HGI: Carbohydrate 59.3 ± 2.4 vs. 69.8 ± 3.9 and 72.7 ± 3.9 g; Fat 22.7 ± 2.0 vs. 18.5 ± 1.7 and 17.6 ± 1.3 g; P < 0.05). In conclusion, the presence of fructose in a LGI breakfast resulted in similar substrate utilization during subsequent brisk walking with that induced by a HGI breakfast. It appears that both the GI and fructose content in a breakfast individually affect substrate utilization during subsequent moderate intensity exercise.

Glycaemic index and glycaemic load of breakfast predict cognitive function and mood in school children: a randomised controlled trial

The macronutrient composition of a breakfast that could facilitate performance after an overnight fast remains unclear. As glucose is the brain's major energy source, the interest is in investigating meals differing in their blood glucose-raising potential. Findings vary due to unaccounted differences in glucoregulation, arousal and cortisol secretion. We investigated the effects of meals differing in glycaemic index (GI) and glycaemic load (GL) on cognition and mood in school children. A total of seventy-four school children were matched and randomly allocated either to the high-GL or low-GL group. Within each GL group, children received high-GI and low-GI breakfasts. Cognitive function (CF) and mood were measured 95-140min after breakfast. Blood glucose and salivary cortisol were measured at baseline, before and after the CF tests. Repeated-measures ANOVA was used to identify differences in CF, mood, glucose and cortisol levels between the breakfasts. Low-GI meals predicted feeling more alert and happy, and less nervous and thirsty (P<0·05 for each); high-GL meals predicted feeling more confident, and less sluggish, hungry and thirsty (P<0·05 for each). High-GL (P<0·001) and high-GI (P=0·05) meals increased glucose levels 90min after breakfast, and high-GI meals increased cortisol levels (P<0·01). When baseline mood, glucose and cortisol levels were considered, low-GI meals predicted better declarative-verbal memory (P=0·03), and high-GI meals better vigilance (P<0·03); observed GI effects were valid across GL groups. GI effects on cognition appear to be domain specific. On balance, it would appear that the low-GI high-GL breakfast may help to improve learning, and of potential value in informing government education policies relating to dietary recommendations and implementation concerning breakfast.

Glycemic Index and Glycemic Load Used in Combination to Characterize Metabolic Responses of Mixed Meals in Healthy Lean Young Adults

Background: Glycemic index (GI) and glycemic load (GL) have been independently assessed with regard to their metabolic effects and their associations with disease risk. Because a low-GI high-carbohydrate and a high-GI low-carbohydrate food/meal can produce the same GL, we propose that these 2 concepts should be used in conjunction to characterize the carbohydrate quality of mixed meals.Objective: The aim of this study was to measure postprandial glucose, insulin, and cortisol responses of meals differing in both GI and GL over a period of 3 hours (every 15 minutes for the first hour, and every 30 minutes subsequently), and to investigate the validity of methods of calculating GI and GL by measuring the cumulative incremental area under the curve (iAUC) for glucose and insulin (0–2 hours and 2–3 hours postprandially).Methods: A total of 10 healthy lean young adults (5 males, 5 females) participated. Breakfast meals were designed to differ in terms of GI and GL based on a 2 × 2 grid with a single elaboration: low-GI high-GL (M1); high-GI high-GL (M2a) of similar GL to M1; high-GI high-GL (M2b) of similar macronutrient composition to M1 (the elaboration); low-GI low-GL (M3); and high-GI low-GL (M4). The 5 breakfast meals were administered in a double-blind randomized crossover design. Repeated measures analysis of variance was performed to investigate differences in metabolic response between low- versus high-GI and between low- versus high-GL breakfast meals (and GI × GL interactions), with GI and GL used as within-subject factors.Results: High-GL meals increased glucose iAUC and insulin iAUC in both immediate (0–2 hours) (p < 0.01, p < 0.001, respectively) and middle postabsorptive periods (2–3 hours) (p = 0.04, p = 0.02, respectively) compared with low-GL meals. GI meals were not associated with glucose iAUC 0 to 2 hours (p = 0.37) and 2 to 3 hours (p = 0.81) postprandially. GI meals were not associated with insulin iAUC 0 to 2 hours postprandially (p = 0.81); in contrast, high-GI meals increased insulin iAUC 2 to 3 hours postprandially (p = 0.03) compared with low-GI meals. No significant differences were noted in cortisol responses, GI × GL interactions, or effect modification by gender.Conclusions: These findings highlight the need for further investigation of meals/diets differing in both GI and GL to characterize metabolic responses and potential health effects.

Evidence for a second meal cognitive effect: glycaemic responses to high and low glycaemic index evening meals are associated with cognition the following morning

Low glycaemic index (GI) foods consumed at breakfast can enhance memory in comparison to high-GI foods; however, the impact of evening meal GI manipulations on cognition the following morning remains unexplored. Fourteen healthy males consumed a high-GI evening meal or a low-GI evening meal in a counterbalanced order on two separate evenings. Memory and attention were assessed before and after a high-GI breakfast the following morning. The high-GI evening meal elicited significantly higher evening glycaemic responses than the low-GI evening meal. Verbal recall was better the morning following the high-GI evening meal compared to after the low-GI evening meal. In summary, the GI of the evening meal was associated with memory performance the next day, suggesting a second meal cognitive effect. The present findings imply that an overnight fast may not be sufficient to control for previous nutritional consumption.