Effect of the glycemic index of carbohydrates on day-long (10 h) profiles of plasma glucose, insulin, cholecystokinin and ghrelin

Nutrient-Based Appetite Regulation

Regulation of appetite is dependent on crosstalk between the gut and the brain, which is a pathway described as the gut-brain axis (GBA). Three primary appetite-regulating hormones that are secreted in the gut as a response to eating a meal are glucagon-like peptide 1 (GLP-1), cholecystokinin (CCK), and peptide YY (PYY). When these hormones are secreted, the GBA responds to reduce appetite. However, secretion of these hormones and the response of the GBA can vary depending on the types of nutrients consumed. This narrative review describes how the gut secretes GLP-1, CCK, and PYY in response to proteins, carbohydrates, and fats. In addition, the GBA response based on the quality of the meal is described in the context of which meal types produce greater appetite suppression. Last, the beneficiary role of exercise as a mediator of appetite regulation is highlighted.

Higher Carbohydrate Amount and Lower Glycemic Index Increase Hunger, Diet Satisfaction, and Heartburn in Overweight and Obese Adults in the OmniCarb Randomized Clinical Trial

BACKGROUND

The Dietary Approaches to Stop Hypertension (DASH) diet, a high-carbohydrate diet, is highly recommended based on its cardiovascular risk benefits, yet adherence remains persistently low. How subjective impressions of this diet contribute to adherence has not been thoroughly explored. The OmniCarb trial, which compared DASH-style diets varying in glycemic index (GI) and carbohydrate amount, surveyed subjective impressions of such diets.

OBJECTIVES

We examined the effects of GI and carbohydrate amount on qualitative aspects of diet acceptability through secondary outcomes in the OmniCarb trial.

METHODS

OmniCarb was a randomized, crossover trial of 4 DASH-style diets varying by GI (≥65 compared with ≤45) and carbohydrate amount (40% compared with 58% kcal) in overweight or obese (BMI ≥25 kg/m2) adults (n = 163). Participants consumed each diet in random order over 5-wk periods, separated by 2-wk washouts. At baseline and the end of each feeding period, participants rated hunger, diet satisfaction, and gastrointestinal symptoms (diarrhea/loose stools, constipation, bloating, nausea, and heartburn).

RESULTS

Participant mean age was 52 y, with 52% women, 51% non-Hispanic black, and 56% obese (BMI ≥30). Compared with baseline, all intervention diets decreased heartburn, increased diarrhea/loose stools, and increased bloating, but did not significantly affect constipation or nausea. Compared with lower carbohydrate diets, higher carbohydrate diets increased hunger (RR: 1.16; 95% CI: 1.04, 1.30), increased diet satisfaction (RR: 1.10; 95% CI: 1.01, 1.20), and increased heartburn (RR: 1.49; 95% CI: 1.09, 2.04). Compared with lower GI diets, higher GI diets did not affect hunger (RR: 0.92; 95% CI: 0.83, 1.02), decreased diet satisfaction (RR: 0.83; 95% CI: 0.75, 0.92), and did not affect heartburn (RR: 0.89; 95% CI: 0.70, 1.13). There were no between-diet differences for diarrhea/loose stools, constipation, bloating, and nausea.

CONCLUSIONS

Although a higher carbohydrate amount in DASH-style diets can increase diet satisfaction, it can also decrease satiety and increase heartburn in adults with overweight or obesity.This trial is registered at clinicaltrials.gov as NCT00608049.

The effect of a low glycaemic index diet on reducing day-long glycaemia in healthy young adults: A randomized crossover trial

AIM

To compare the effect of a low glycaemic index (LGI) diet on reducing day-long glycaemia with a macronutrient-matched high glycaemic index (HGI) diet, using customized meal delivery to ensure compliance.

MATERIALS AND METHODS

We conducted a single-blinded, randomized crossover trial in 14 healthy adults (57% female) with a mean ± SD age of 21.6 ± 1.7 years. A flash glucose monitoring sensor was installed on the subjects on day 1 to capture the interstitial glucose level every 15 minutes for 14 days. Subjects were randomized to receive an LGI (dietary GI = 40) or HGI (dietary GI = 60) diet (three meals and two snacks) from day 2 for 5 consecutive days, followed by a 2-day washout, then switched to the alternative diet for another 5 days. A paired t-test was used to test the differences in the incremental area under the curve (iAUC) of glucose, postprandial glucose (PPG) concentration and maximum postprandial glucose rise (MPGR) between the LGI and HGI periods.

RESULTS

Subjects had lower iAUC for average day-long glycaemia during the LGI intervention period compared with the HGI period (mean ± SD, 865 ± 297 vs. 1024 ± 267 mmol x min/L; P = .047). PPG for breakfast and snack 2, and MPGR for breakfast, snack 2 and dinner, were lower in the LGI period.

CONCLUSIONS

In young healthy adults, following an LGI diet resulted in lower average day-long glycaemia compared with a macronutrient-matched HGI diet. Our results support the use of LGI diets to reduce the risk of developing glucose intolerance.

Diet pattern may affect fasting insulin in a large sample of black and white adults

OBJECTIVE

Dietary modification of insulin resistance may be a strategy for reducing chronic disease. For this study, we tested the hypothesis that higher fasting insulin, a marker for insulin resistance, would be related to diet patterns with a high proportion of carbohydrates, those with a high glycemic index, and those characterized by added sugar and processed starches.

STUDY DESIGN

Data were analyzed on 13,528 nondiabetic participants of the REasons for Geographic and Ethnic Differences in Stroke (REGARDS), an observational study of adults aged ≥45 years residing in 1855 counties across the continental USA. Information on habitual diet was collected using the Block 98 Food Frequency Questionnaire. Percent energy from carbohydrate, glycemic index, and glycemic load were determined for each participant, as well as adherence to five established diet patterns. Logistic regression was used to examine associations of baseline diet characteristics with odds for high fasting insulin [quartiles 3 and 4 (median = 98.9 pmol/L) vs. quartile 1], after adjusting for covariates.

RESULT

Greater percent carbohydrate, glycemic index, and glycemic load, and adherence to sweets/fat and southern diet patterns, was associated with greater odds for high insulin (P for trend <0.05 to <0.0001), whereas adherence to the plant-based and alcohol/salad patterns was associated with lower odds for high insulin (P for linear trend <0.0001).

CONCLUSION

In conclusion, diet pattern is associated with fasting insulin. Future studies are needed to determine if diet interventions designed to lower insulin, perhaps based on the patterns identified in this study, can improve risk for chronic disease.

New Insight into Diabetes Management: From Glycemic Index to Dietary Insulin Index

BACKGROUND

Despite efforts to control hyperglycemia, diabetes management is still challenging. This may be due to focusing on reducing hyperglycemia and neglecting the importance of hyperinsulinemia; while insulin resistance and resultant hyperinsulinemia preceded diabetes onset and may contribute to disease pathogenesis.

OBJECTIVE

The present narrative review attempts to provide a new insight into the management of diabetes by exploring different aspects of glycemic index and dietary insulin index.

RESULTS

The current data available on this topic is limited and heterogeneous. Conventional diet therapy for diabetes management is based on reducing postprandial glycemia through carbohydrate counting, choosing foods with low-glycemic index and low-glycemic load. Since these indicators are only reliant on the carbohydrate content of foods and do not consider the effects of protein and fat on the stimulation of insulin secretion, they cannot provide a comprehensive approach to determine the insulin requirements.

CONCLUSION

Selecting foods based on carbohydrate counting, glycemic index or glycemic load are common guides to control glycemia in diabetic patients, but neglect the insulin response, thus leading to failure in diabetes management. Therefore, paying attention to insulinemic response along with glycemic response seems to be more effective in managing diabetes.

Relevance of the Glycemic Index and Glycemic Load for Body Weight, Diabetes, and Cardiovascular Disease

Despite initial enthusiasm, the relationship between glycemic index (GI) and glycemic response (GR) and disease prevention remains unclear. This review examines evidence from randomized, controlled trials and observational studies in humans for short-term (e.g., satiety) and long-term (e.g., weight, cardiovascular disease, and type 2 diabetes) health effects associated with different types of GI diets. A systematic PubMed search was conducted of studies published between 2006 and 2018 with key words glycemic index, glycemic load, diabetes, cardiovascular disease, body weight, satiety, and obesity. Criteria for inclusion for observational studies and randomized intervention studies were set. The search yielded 445 articles, of which 73 met inclusion criteria. Results suggest an equivocal relationship between GI/GR and disease outcome. The strongest intervention studies typically find little relationship among GI/GR and physiological measures of disease risk. Even for observational studies, the relationship between GI/GR and disease outcomes is limited. Thus, it is unlikely that the GI of a food or diet is linked to disease risk or health outcomes. Other measures of dietary quality, such as fiber or whole grains may be more likely to predict health outcomes. Interest in food patterns as predictors of health benefits may be more fruitful for research to inform dietary guidance.

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

BACKGROUND AND AIM

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).

METHODS

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 120 min, and satiety and satiation were evaluated through a visual analogue scale.

RESULTS

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 1940 mg/dL × 120 min, p = 0.022) and in mean glycemia evaluated at 30, 60 and 120 min. Moreover, in the low GI stage 8 of 10 patients achieved a 2 h postprandial glycemia lower than 180 mg/dL, without statistical significance. A nonsignificant increase of 12.7% (Δ 1.06 cm, p = 0.271) in satiety at 120 min in the low GI stage was observed.

CONCLUSION

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.

Effects of a healthier snack on snacking habits and glycated Hb (HbA1c): a 6-week intervention study

Dietary behaviour modification may change eating habits and reduce the impact of poor nutrition. This study aimed to evaluate the effects of daily consumption of a healthier snack bar on snacking habits and glycated Hb (HbA1c) within a 6-week intervention. In all, twenty-eight participants were randomly allocated to two groups to either consume the bars as the main snack for 6 weeks (n 14) or receipt of the bars was delayed for 6 weeks (n 14) following a stepped-wedge design. All participants had HbA1c concentrations measured at weeks -1, 0, 4, 6, 10 and 12. A short dietary habits questionnaire was self-completed at weeks 0, 6 and 12. Participants consumed the bars they received instead of other snacks, and found that the healthier snack bar was acceptable as part of their daily dietary pattern. Over the 12 weeks, there was a significant reduction in intake of biscuits, cakes and pies (approximately 2 servings/week, P<0·05) in both groups. Fruit juice intake was reduced (approximately 1 serving/week, P=0·029) in the first group. In all, twenty participants (71·4 %) experienced a decrease (n 15) or no change (n 5) in HbA1c (range 0-4 mmol/mol), whereas eight participants experienced an increase in HbA1c (range 0·5-2·5 mmol/mol). There was high compliance with the healthier snack intervention and a trend towards a favourable effect on glucose homoeostasis. Habitual snacking behaviour has the potential to be improved through changes in the food supply, and in the longer term may reduce the impact of poor nutrition on public health.

Effects of high vs low glycemic index of dietary carbohydrate on cardiovascular disease risk factors and insulin sensitivity: the OmniCarb randomized clinical trial

IMPORTANCE

Foods that have similar carbohydrate content can differ in the amount they raise blood glucose. The effects of this property, called the glycemic index, on risk factors for cardiovascular disease and diabetes are not well understood.

OBJECTIVE

To determine the effect of glycemic index and amount of total dietary carbohydrate on risk factors for cardiovascular disease and diabetes.

DESIGN, SETTING, AND PARTICIPANTS

Randomized crossover-controlled feeding trial conducted in research units in academic medical centers, in which 163 overweight adults (systolic blood pressure, 120-159 mm Hg) were given 4 complete diets that contained all of their meals, snacks, and calorie-containing beverages, each for 5 weeks, and completed at least 2 study diets. The first participant was enrolled April 1, 2008; the last participant finished December 22, 2010. For any pair of the 4 diets, there were 135 to 150 participants contributing at least 1 primary outcome measure.

INTERVENTIONS

(1) A high-glycemic index (65% on the glucose scale), high-carbohydrate diet (58% energy); (2) a low-glycemic index (40%), high-carbohydrate diet; (3) a high-glycemic index, low-carbohydrate diet (40% energy); and (4) a low-glycemic index, low-carbohydrate diet. Each diet was based on a healthful DASH-type diet.

MAIN OUTCOMES AND MEASURES

The 5 primary outcomes were insulin sensitivity, determined from the areas under the curves of glucose and insulin levels during an oral glucose tolerance test; levels of low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and triglycerides; and systolic blood pressure.

RESULTS

At high dietary carbohydrate content, the low- compared with high-glycemic index level decreased insulin sensitivity from 8.9 to 7.1 units (-20%, P = .002); increased LDL cholesterol from 139 to 147 mg/dL (6%, P ≤ .001); and did not affect levels of HDL cholesterol, triglycerides, or blood pressure. At low carbohydrate content, the low- compared with high-glycemic index level did not affect the outcomes except for decreasing triglycerides from 91 to 86 mg/dL (-5%, P = .02). In the primary diet contrast, the low-glycemic index, low-carbohydrate diet, compared with the high-glycemic index, high-carbohydrate diet, did not affect insulin sensitivity, systolic blood pressure, LDL cholesterol, or HDL cholesterol but did lower triglycerides from 111 to 86 mg/dL (-23%, P ≤ .001).

CONCLUSIONS AND RELEVANCE

In this 5-week controlled feeding study, diets with low glycemic index of dietary carbohydrate, compared with high glycemic index of dietary carbohydrate, did not result in improvements in insulin sensitivity, lipid levels, or systolic blood pressure. In the context of an overall DASH-type diet, using glycemic index to select specific foods may not improve cardiovascular risk factors or insulin resistance.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00608049.

Return of hunger following a relatively high carbohydrate breakfast is associated with earlier recorded glucose peak and nadir

The aim of this study is to test the hypothesis that a breakfast meal with high carbohydrate/low fat results in an earlier increase in postprandial glucose and insulin, a greater decrease below baseline in postprandial glucose, and an earlier return of appetite, compared with a low carbohydrate/high fat meal. Overweight but otherwise healthy adults (n = 64) were maintained on one of two eucaloric diets: high carbohydrate/low fat (HC/LF; 55:27:18% kcals from carbohydrate:fat:protein) versus low carbohydrate/high fat (LC/HF; 43:39:18% kcals from carbohydrate:fat:protein). After 4 weeks of acclimation to the diets, participants underwent a meal test during which circulating glucose and insulin and self-reported hunger and fullness, were measured before and after consumption of breakfast from their assigned diets. The LC/HF meal resulted in a later time at the highest and lowest recorded glucose, higher glucose concentrations at 3 and 4 hours post meal, and lower insulin incremental area under the curve. Participants consuming the LC/HF meal reported lower appetite 3 and 4 hours following the meal, a response that was associated with the timing of the highest and lowest recorded glucose. Modest increases in meal carbohydrate content at the expense of fat content may facilitate weight gain over the long-term by contributing to an earlier rise and fall of postprandial glucose concentrations and an earlier return of appetite.

Effects of ingesting low glycemic index carbohydrate food for the sahur meal on subjective, metabolic and physiological responses, and endurance performance in Ramadan fasted men

PURPOSE

To investigate the effect of low glycemic index (LGI) carbohydrate meal on subjective, metabolic and physiological responses, and endurance performance in the Ramadan fasted state.

METHODS

During Ramadan, 12 Muslim men, in a randomized and crossover design, ingested for the sahur meal (i.e., last meal before commencement of the day's fast), either LGI (glycemic index = 37) or mixed (CON; ∼57) meal of equivalent macro-nutrient. At ∼12 h post-prandial, subjects completed a 60 min continuous run.

RESULTS

There were no significant differences between the two meals for ratings in perceived satiety, fullness, appetite and mood states. During steady-state exercise, there were no significant differences in metabolic and physiological measures. In the time-trial, distance ran was significantly lower in LGI versus CON meal trial, but with a corresponding lower perceived exertion in the LGI trial.

CONCLUSION

Compared to CON, ingesting LGI as the sahur meal did not provide any metabolic, physiological or performance benefits during endurance run performed 12 h post-prandial in Ramadan fasted state.

The role of metabonomics as a tool for augmenting nutritional information in epidemiological studies

Most chronic diseases have been demonstrated to have a link to nutrition. Within food and nutritional research there is a major driver to understand the relationship between diet and disease in order to improve health of individuals. However, the lack of accurate dietary intake assessment in free-living populations, makes accurate estimation of how diet is associated with disease risk difficulty. Thus, there is a pressing need to find solutions to the inaccuracy of dietary reporting. Metabolic profiling of urine or plasma can provide an unbiased approach to characterizing dietary intake and various high-throughput analytical platforms have been used in order to implement targeted and nontargeted assays in nutritional clinical trials and nutritional epidemiology studies. This review describes first the challenges presented in interpreting the relationship between diet and health within individual and epidemiological frameworks. Second, we aim to explore how metabonomics can benefit different types of nutritional studies and discuss the critical importance of selecting appropriate analytical techniques in these studies. Third, we propose a strategy capable of providing accurate assessment of food intake within an epidemiological framework in order establish accurate associations between diet and health.

Effect of a low glycaemic index diet in gestational diabetes mellitus on post-natal outcomes after 3 months of birth: a pilot follow-up study

A low glycaemic index (LGI) diet during pregnancy complicated by gestational diabetes mellitus (GDM) may offer benefits to the mother and infant pair beyond those during pregnancy. We aimed to investigate the effect of an LGI diet during pregnancy complicated with GDM on early post-natal outcomes. Fifty-eight women (age: 23-41 years; mean ± SD pre-pregnancy body mass index: 24.5 ± 5.6 kg m(-2) ) who had GDM and followed either an LGI diet (n = 33) or a conventional high-fibre diet (HF; n = 25) during pregnancy had a 75-g oral glucose tolerance test and blood lipid tests at 3 months post-partum. Anthropometric assessments were conducted for 55 mother-infant pairs. The glycaemic index of the antenatal diets differed modestly (mean ± SD: 46.8 ± 5.4 vs. 52.4 ± 4.4; P < 0.001), but there were no significant differences in any of the post-natal outcomes. In conclusion, an LGI diet during pregnancy complicated by GDM has outcomes similar to those of a conventional healthy diet. Adequately powered studies should explore the potential beneficial effects of LGI diet on risk factors for chronic disease.

Reducing the glycemic index or carbohydrate content of mixed meals reduces postprandial glycemia and insulinemia over the entire day but does not affect satiety

OBJECTIVE

We evaluated the effects of mixed meals differing in glycemic index (GI) and carbohydrate content on postprandial serum glucose and insulin response, hunger, and satiety over the course of a 12-h day.

RESEARCH DESIGN AND METHODS

In this randomized crossover trial, 26 overweight or obese adults received four diets in random order (high GI, high carbohydrate [HGI-HC]; high GI, low carbohydrate [HGI-LC]; low GI, high carbohydrate [LGI-HC]; and low GI, low carbohydrate [LGI-LC]). All meals were prepared by a metabolic kitchen. Participants received breakfast, lunch, and dinner over the course of a 12-h day. Primary outcomes were postprandial serum glucose and insulin quantified as area under the curve. Hunger, fullness, and satiety were assessed by visual analog scale.

RESULTS

The HGI-LC, LGI-HC, and LGI-LC diets significantly reduced glucose and insulin area under the curve compared with the HGI-HC diet (P < 0.001 for all comparisons). There were no significant differences in ratings of hunger, fullness, or satiety between the different dietary treatments.

CONCLUSIONS

Reducing the GI or carbohydrate content of mixed meals reduces postprandial glycemia and insulinemia, and these changes can be sustained over the course of an entire day. However, there were no differences in subjective hunger and satiety ratings between the diets. These results demonstrate that maintaining a low GI or glycemic load diet is an effective method of controlling serum glucose and insulin levels.

The individual and combined effects of glycemic index and protein on glycemic response, hunger, and energy intake

Although high protein and low glycemic index (GI) foods are thought to promote satiety, little is known about the effects of GI, protein, and their interaction on hunger and energy intake several hours following a mixed meal. This study investigated the long term effects of GI, protein, and their combined effects on glucose, insulin, hunger, and energy intake in healthy, sedentary, overweight, and obese adults (BMI of 30.9 ± 3.7 kg/m(2)). Sixteen individuals participated separately in four testing sessions after an overnight fast. The majority (75%) were non-Hispanic Blacks. Each consumed one of four breakfast meals (high GI/low protein, high GI/high protein, low GI/low protein, low GI/high protein) in random order. Visual analog scales (VAS) and blood samples were taken at baseline, 15 min, and at 30 min intervals over 4 h following the meal. After 4 h, participants were given the opportunity to consume food ad libitum from a buffet style lunch. Meals containing low GI foods produced a smaller glucose (P < 0.002) and insulin (P = 0.0001) response than meals containing high GI foods. No main effects for protein or interactions between GI and protein were observed in glucose or insulin responses, respectively. The four meals had no differential effect on observed energy intake or self-reported hunger, satiety, and prospective energy intake. Low GI meals produced the smallest postprandial increases in glucose and insulin. There were no effects for GI, protein, or their interaction on appetite or energy intake 4 h after breakfast.

Food intake, postprandial glucose, insulin and subjective satiety responses to three different bread-based test meals

The effect of bread consumption on overall food intake is poorly understood. The aim of this study was to measure postprandial food intake after a set breakfast containing three different breads. Ten males and 10 females aged 20.1-44.8 years, BMI 18.4-24.8 kg/m(2), consumed two slices of White Bread, Bürgen Wholemeal and Seeds Bread or Lupin Bread (all 1300 kJ) with 10 g margarine and 30 g strawberry jam. Fullness and hunger responses and were measured before and during the test breakfasts. Glucose and insulin responses (incremental area under each two-hour curve (iAUC)) were calculated. Food intake was measured and energy and nutrient intake determined at a buffet meal two hours later. Subjects consumed significantly less energy after the Bürgen Bread meal compared to the White Bread meal (2548 ± 218 vs. 3040±328kJ, Bürgen Bread vs. White Bread, P<0.05). There were higher fullness responses for the Lupin Bread (P<0.01), and the Bürgen Bread (P<0.05) compared with the White Bread. Lupin Bread and Bürgen Bread produced smaller postprandial glucose responses (79 ± 7, 74 ± 4, 120 ± 10 mmol/L min iAUC, Lupin, Bürgen and White Bread respectively, P<0.01). Differences in insulin responses were also observed (6145 ± 1048, 6471 ± 976, 9674 ± 1431 pmol/L min iAUC, Lupin, Bürgen and White Bread respectively, P<0.01). Equal-energy portions of three different commercially available breads differed in their short-term satiation capacity. Further studies are needed to demonstrate any potential benefit for weight management.

Genetic polymorphisms in the hypothalamic pathway in relation to subsequent weight change--the DiOGenes study

Background

Single nucleotide polymorphisms (SNPs) in genes encoding the components involved in the hypothalamic pathway may influence weight gain and dietary factors may modify their effects.

Aim

We conducted a case-cohort study to investigate the associations of SNPs in candidate genes with weight change during an average of 6.8 years of follow-up and to examine the potential effect modification by glycemic index (GI) and protein intake.

Methods and Findings

Participants, aged 20–60 years at baseline, came from five European countries. Cases (‘weight gainers’) were selected from the total eligible cohort (n = 50,293) as those with the greatest unexplained annual weight gain (n = 5,584). A random subcohort (n = 6,566) was drawn with the intention to obtain an equal number of cases and noncases (n = 5,507). We genotyped 134 SNPs that captured all common genetic variation across the 15 candidate genes; 123 met the quality control criteria. Each SNP was tested for association with the risk of being a ‘weight gainer’ (logistic regression models) in the case-noncase data and with weight gain (linear regression models) in the random subcohort data. After accounting for multiple testing, none of the SNPs was significantly associated with weight change. Furthermore, we observed no significant effect modification by dietary factors, except for SNP rs7180849 in the neuromedin β gene (NMB). Carriers of the minor allele had a more pronounced weight gain at a higher GI (P = 2×10⁻⁷).

Conclusions

We found no evidence of association between SNPs in the studied hypothalamic genes with weight change. The interaction between GI and NMB SNP rs7180849 needs further confirmation.

Glycemic index and pregnancy: a systematic literature review

Background/Aim. Dietary glycemic index (GI) has received considerable research interest over the past 25 years although its application to pregnancy outcomes is more recent. This paper critically evaluates the current evidence regarding the effect of dietary GI on maternal and fetal nutrition. Methods. A systematic literature search using MEDLINE, EMBASE, CINAHL, Cochrane Library, SCOPUS, and ISI Web of Science, from 1980 through September 2010, was conducted. Results. Eight studies were included in the systematic review. Two interventional studies suggest that a low-GI diet can reduce the risk of large-for-gestational-age (LGA) infants in healthy pregnancies, but one epidemiological study reported an increase in small-for-gestational-age (SGA) infants. Evidence in pregnancies complicated by gestational diabetes mellitus (GDM), though limited (n = 3), consistently supports the advantages of a low-GI diet. Conclusion. There is insufficient evidence to recommend a low-GI diet during normal pregnancy. In pregnancy complicated by GDM, a low-GI diet may reduce the need for insulin without adverse effects on pregnancy outcomes. Until larger-scale intervention trials are completed, a low-GI diet should not replace the current recommended pregnancy diets from government and health agencies. Further research regarding the optimal time to start a low-GI diet for maximum protection against adverse pregnancy outcomes is warranted.

Optimal dietary approaches for prevention of type 2 diabetes: a life-course perspective

In recent years, several alternative dietary approaches, including high-protein and low-glycaemic-load diets, have produced faster rates of weight loss than traditional low-fat, high-carbohydrate diets. These diets share an under-recognised unifying mechanism: the reduction of postprandial glycaemia and insulinaemia. Similarly, some food patterns and specific foods (potatoes, white bread, soft drinks) characterised by hyperglycaemia are associated with higher risk of adiposity and type 2 diabetes. Profound compensatory hyperinsulinaemia, exacerbated by overweight, occurs during critical periods of physiological insulin resistance such as pregnancy and puberty. The dramatic rise in gestational diabetes and type 2 diabetes in the young may therefore be traced to food patterns that exaggerate postprandial glycaemia and insulinaemia. The dietary strategy with the strongest evidence of being able to prevent type 2 diabetes is not the accepted low-fat, high-carbohydrate diet, but alternative dietary approaches that reduce postprandial glycaemia and insulinaemia without adversely affecting other risk factors.

Food insulin index: physiologic basis for predicting insulin demand evoked by composite meals

BACKGROUND

Diets that provoke less insulin secretion may be helpful in the prevention and management of diabetes. A physiologic basis for ranking foods according to insulin "demand" could therefore assist further research.

OBJECTIVE

We assessed the utility of a food insulin index (FII) that was based on testing isoenergetic portions of single foods (1000 kJ) in predicting the insulin demand evoked by composite meals.

DESIGN

Healthy subjects (n = 10 or 11 for each meal) consumed 13 different isoenergetic (2000 kJ) mixed meals of varying macronutrient content. Insulin demand predicted by the FII of the component foods or by carbohydrate counting and glycemic load was compared with observed insulin responses.

RESULTS

Observed insulin responses (area under the curve relative to white bread: 100) varied over a 3-fold range (from 35 +/- 5 to 116 +/- 26) and were strongly correlated with insulin demand predicted by the FII of the component foods (r = 0.78, P = 0.0016). The calculated glycemic load (r = 0.68, P = 0.01) but not the carbohydrate content of the meals (r = 0.53, P = 0.064) also predicted insulin demand.

CONCLUSIONS

The relative insulin demand evoked by mixed meals is best predicted by a physiologic index based on actual insulin responses to isoenergetic portions of single foods. In the context of composite meals of similar energy value, but varying macronutrient content, carbohydrate counting was of limited value.

Endosperm and whole grain rye breads are characterized by low post-prandial insulin response and a beneficial blood glucose profile

BACKGROUND

Rye products have previously been shown to induce comparatively low post-prandial insulin responses; irrespectively of their glycaemic indices (GI). However, the mechanism behind this lowered insulin demand remains unknown. An improved insulin economy might contribute to the benefits seen in epidemiological studies with whole grain diets on metabolic risk factors and weight regulation. The objective of this study was to explore the mechanism for a reduced post-prandial insulin demand with rye products.

METHODS

12 healthy subjects were given flour based rye products made from endosperm, whole grain or bran, produced with different methods (baking, simulated sour-dough baking and boiling) as breakfasts in random order in a cross-over design. White wheat bread (WWB) was used as a reference. Blood glucose, serum insulin, plasma ghrelin and subjective satiety were measured during 180 minutes. To evaluate the course of post-meal glycaemia, a measure of the glycaemic profile (GP) was introduced defined as the duration for the incremental post-prandial blood glucose response divided with the blood glucose incremental peak (min/mM).

RESULTS

The study shows that whole grain rye breads and endosperm rye products induced significantly (p < 0.05) lower insulinaemic indices (II's) than WWB. Rye bran bread (RBB) produced significantly higher II compared with all the other rye products. Furthermore, the acute insulin response showed better correlations with the GP than with the GI of the products. The endosperm rye bread and the whole grain rye bread with lactic acid induced a significantly higher GP than RBB, WWB, white wheat- and whole grain rye porridge, respectively. A low insulin incremental peak was associated with less severe late post-prandial hypoglycaemia (r = 0.38, p < 0.001), and hypoglycaemia was negatively correlated to subjective satiety at 180 min (r = -0.28, p < 0.05). A low insulin incremental peak was also associated with a milder recovery of plasma ghrelin in the late post-prandial phase (180 min, r = 0.34, p < 0.01).

CONCLUSION

Our study shows that endosperm and whole grain rye products induce low acute insulinaemic responses and improved glycaemic profiles. The results also suggest that the rye products possess beneficial appetite regulating properties. Further studies are needed to identify the unknown property or bioactive component(s) responsible for these beneficial metabolic features of rye.