Influence of glycemic index/load on glycemic response, appetite, and food intake in healthy humans

Ultraprocessed Foods and Obesity Risk: A Critical Review of Reported Mechanisms

Epidemiologic evidence supports a positive association between ultraprocessed food (UPF) consumption and body mass index. This has led to recommendations to avoid UPFs despite very limited evidence establishing causality. Many mechanisms have been proposed, and this review critically aimed to evaluate selected possibilities for specificity, clarity, and consistency related to food choice (i.e., low cost, shelf-life, food packaging, hyperpalatability, and stimulation of hunger/suppression of fullness); food composition (i.e., macronutrients, food texture, added sugar, fat and salt, energy density, low-calorie sweeteners, and additives); and digestive processes (i.e., oral processing/eating rate, gastric emptying time, gastrointestinal transit time, and microbiome). For some purported mechanisms (e.g., fiber content, texture, gastric emptying, and intestinal transit time), data directly contrasting the effects of UPF and non-UPF intake on the indices of appetite, food intake, and adiposity are available and do not support a unique contribution of UPFs. In other instances, data are not available (e.g., microbiome and food additives) or are insufficient (e.g., packaging, food cost, shelf-life, macronutrient intake, and appetite stimulation) to judge the benefits versus the risks of UPF avoidance. There are yet other evoked mechanisms in which the preponderance of evidence indicates ingredients in UPFs actually moderate body weight (e.g., low-calorie sweetener use for weight management; beverage consumption as it dilutes energy density; and higher fat content because it reduces glycemic responses). Because avoidance of UPFs holds potential adverse effects (e.g., reduced diet quality, increased risk of food poisoning, and food wastage), it is imprudent to make recommendations regarding their role in diets before causality and plausible mechanisms have been verified.

Insights into the constellating drivers of satiety impacting dietary patterns and lifestyle

Food intake and body weight regulation are of special interest for meeting today's lifestyle essential requirements. Since balanced energy intake and expenditure are crucial for healthy living, high levels of energy intake are associated with obesity. Hence, regulation of energy intake occurs through short- and long-term signals as complex central and peripheral physiological signals control food intake. This work aims to explore and compile the main factors influencing satiating efficiency of foods by updating recent knowledge to point out new perspectives on the potential drivers of satiety interfering with food intake regulation. Human internal factors such as genetics, gender, age, nutritional status, gastrointestinal satiety signals, gut enzymes, gastric emptying rate, gut microbiota, individual behavioral response to foods, sleep and circadian rhythms are likely to be important in determining satiety. Besides, the external factors (environmental and behavioral) impacting satiety efficiency are highlighted. Based on mechanisms related to food consumption and dietary patterns several physical, physiological, and psychological factors affect satiety or satiation. A complex network of endocrine and neuroendocrine mechanisms controls the satiety pathways. In response to food intake and other behavioral cues, gut signals enable endocrine systems to target the brain. Intestinal and gastric signals interact with neural pathways in the central nervous system to halt eating or induce satiety. Moreover, complex food composition and structures result in considerable variation in satiety responses for different food groups. A better understanding of foods and factors impacting the efficiency of satiety could be helpful in making smart food choices and dietary recommendations for a healthy lifestyle based on updated scientific evidence.

Activation of gastrointestinal ileal brake response with dietary slowly digestible carbohydrates, with no observed effect on subjective appetite, in an acute randomized, double-blind, crossover trial

PURPOSE

To test the hypothesis that oral ingestion of slowly digestible carbohydrates (SDCs) that reach the ileum triggers the ileal brake as indicated by delayed gastric emptying, reduced glycemic response, and decreased subjective appetite.

METHODS

The study was a five-arm, randomized, double-blind, crossover trial with a 1-week washout period between treatments (n = 20; 9 females, 11 males). Five treatments consisted of three SDC ingredients [raw corn starch, isomaltooligosaccharide (IMO), sucromalt], and an IMO/sucromalt combination, shown in vitro to have slow and extended digestion profiles, and a rapidly digestible carbohydrate control (maltodextrin). Carbohydrates (26 g) were incorporated into yogurt [300 g total; carbohydrate (~ 77 g), fat (~ 0.2 g), and protein (~ 9 g)] with closely matched energy content (346 kcal) and viscosity (~ 30,000 cP). Outcomes were measured in a 4 h postprandial period.

RESULTS

Mean gastric half-emptying times were moderately though significantly increased for the raw corn starch and IMO treatments (P < 0.05), but they could be sub-divided into larger effect responder (n = 11) and non-responder groups (n = 9). Longer time for glycemic response to return to baseline was associated with increased gastric half-emptying time in an exploratory subset of data removing gastric half-emptying times > 3.5 h (P = 0.02). No significant differences in appetite ratings were observed.

CONCLUSION

SDCs caused slower gastric emptying rate through activation of the ileal brake, as closely matched semi-solid yogurts were used and only rate of carbohydrate digestion differed. Extending glycemic response through consumption of SDCs was associated with triggering the ileal brake.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03630445, August 2018, retrospectively registered.

L-arabinose and D-xylose: sweet pentoses that may reduce postprandial glucose and insulin responses

Background

Diets inducing high fluctuations in plasma glucose levels are linked to type 2 diabetes. L-arabinose and D-xylose have been hypothesized to inhibit intestinal sucrase activity, delay sucrose digestion, and reduce glycaemic and insulinaemic responses. However, few human studies have assessed this using realistic foods.

Objective

We investigated the effects of the addition of L-arabinose and D-xylose on glucose homeostasis using a fruit-based drink and the effect of L-arabinose using a muffin.

Design

Fifteen males participated in two double-blind, randomized cross-over experiments. In experiment A, three drinks were tested: (1) L-arabinose, (2) D-xylose and (3) control drink. In experiment B, two muffins were tested: (1) L-arabinose and (2) control muffin. All products consisted of ~50 g available carbohydrates, and L-arabinose or D-xylose was added as 10% of sucrose. Pre- and post-ingestive plasma glucose and insulin levels were measured at fixed time points up to 180 min after consumption.

Results

Glucose and insulin peaks were lower after the L-arabinose and D-xylose drink than the control drink (P < 0.01). After consumption of the muffin, glucose responses were not significantly different; however, the insulin peak and incremental area under the curve (iAUC) tended to be lower for the L-arabinose muffin.

Conclusion

L-arabinose and D-xylose are functional ingredients that can potentially lower the post-ingestive glycaemic and insulinaemic responses when added to realistic foods. However, the efficacy of applying L-arabinose appears to depend on the food matrix. Addition of these compounds needs further testing in other foods and in other populations, such as pre-diabetics.

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.

Potential contributions of the methodology to the variability of glycaemic index of foods

Glycaemic index (GI) testing provides a useful point of comparison between carbohydrate sources. For this comparison to be meaningful, the methods used to determine GI values need to be rigorous and consistent between testing events. This requirement has led to increasing standardization of the GI methodology, with an international standard developed in joint consultation with FAO/WHO (ISO 26642:2010) currently the most up to date document. The purpose of this review is to compare the international standard to methods of published studies claiming to have performed a GI test. This analysis revealed that the international standard permits a wide range of choices for researchers when designing a GI testing plan, rather than a single standardized protocol. It has also been revealed that the literature contains significant variation, both between studies and from the international standard for critical aspects of GI testing methodology. The primary areas of variation include; what glucose specification is used, which reference food is used, how much reference food is given, what drink is given during testing, the blood sampling site chosen and what assay and equipment is used to measure blood glucose concentration. For each of these aspects we have explored some of the methodological and physiological implications of these variations. These insights suggest that whilst the international standard has assisted with framing the general parameters of GI testing, further stan-dardization to testing procedures is still required to ensure the continued relevance of the GI to clinical nutrition.

African Cuisine-Centered Insulin Therapy: Expert Opinion on the Management of Hyperglycaemia in Adult Patients with Type 2 Diabetes Mellitus

The prevalence of diabetes in sub-Saharan Africa (SSA) is growing rapidly, and a steadily increasing number of adults are estimated to be living with type 2 diabetes mellitus (T2DM). Insulin therapy is the treatment of choice in patients who present with severe hyperglycaemia and in most of those who do not achieve target goals on oral hypoglycaemic agents. Initiating treatment with the appropriate type of insulin based on the meal patterns and lifestyle of the individual patient is a strategy that is more likely than others to improve glycaemic control and adherence. African cuisine typically has a high carbohydrate load. Given these predominantly carbohydrate-rich food habits, it is essential to modify this dietary pattern whilst at the same time ensuring that insulin therapy is initiated, titrated and maintained in a timely manner, as needed to suit the patient's habits. To date, there are no published clinical guidelines to guide practitioners and patients on tailoring insulin to match the high carbohydrate content in African cuisine. To address this gap, we have reviewed current insulin therapy practices and propose a patient-centric guide to insulin therapy based on African cuisine. A literature search was conducted for studies published in English up to November 2019 that focused on the choice of insulin and its dosing in relation to African foods. All articles extracted were reviewed by an expert group. The recommendation of the expert group was that basal-bolus and premix insulin regimens are best suited to manage post-meal glycaemia in African cuisine. The timing and constituents of the meal, portion sizes, glycaemic load and glycaemic index of meals should be considered when choosing the type of insulin and insulin regimen. Assessment of individual preferences and comorbidities should be prioritised and form an integral part of diabetes management.

Manipulation of fatty acid composition in a high-fat meal does not result in differential alterations in appetite or food intake in normal weight females: A single-blind randomized crossover study

A behavioral concept that generates a path to obesity is eating in the absence of hunger (EAH). One strategy that may be effective in preventing EAH is the manipulation of dietary fatty acid (FA) composition. However, it remains unclear which FA has the greatest impact on both appetite and EAH. Therefore, the purpose of this study was to examine the effect of different dietary FA compositions (monounsaturated, MUFA; polyunsaturated, PUFA; saturated, SFA) on subjective ratings of appetite and subsequent ad libitum eating after a 3 h postprandial period. Sixteen apparently healthy normal weight females between ages 18-40 completed this randomized, single-blind, crossover study. Participants consumed a HF meal (65% energy from fat) rich in SFA, MUFA, and PUFA with an energy content corresponding to 35% of their measured resting metabolic rate on three separate occasions. Visual analog scales were collected while fasted and every 30 min for 3 h during a postprandial period to measure feelings of hunger, fullness, and desire to eat (DTE). Participants were provided an ad libitum buffet meal 3 h after the HF meal. There were no statistically significant differences for ratings of hunger, fullness, or DTE across conditions. Further, there was no significant difference in energy intake during the ad libitum lunch. We conclude that the manipulation of FA composition in a HF meal does not differentially affect appetite sensations or subsequent energy intake.

Ketonemia and Glycemia Affect Appetite Levels and Executive Functions in Overweight Females During Two Ketogenic Diets

OBJECTIVE

This study sought to investigate how glycemia and ketonemia variations during two ketogenic diet protocols affect appetite, executive functions, and mood in young women with overweight.

METHODS

Fifty healthy young females with overweight were randomly assigned to (1) a ketogenic diet without any restriction on energy intake, (2) a commercial energy-restricted ketogenic Mediterranean diet, and (3) an energy-restricted Mediterranean diet for 10 days. A visual analogue scale was used to test appetite, and one mood test and two cognitive tasks (working memory and inhibition control) were performed. Moreover, body composition, fasting blood glucose, and β-hydroxybutyrate (BHB) were measured.

RESULTS

A positive correlation was found between glycemia and appetite (P = 0.019), unfullness score (P =  0.001), and desire to eat (P = 0.030) (pre- and postdiet levels). Postdiet BHB levels showed a positive correlation with fullness score (P = 0.002) and a negative correlation with appetite (P = 0.022) and desire to eat (P = 0.009). A positive correlation was found between prediet levels of glycemia and reaction times in the go-trials of the executive function test (P = 0.018). Postdiet BHB level showed a negative correlation with the accuracy of the no-go trials (P = 0.027).

CONCLUSIONS

Ketogenic diets, compared with a Mediterranean diet, have a greater effect in terms of appetite reduction but might affect inhibition functions.

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.

Macronutrient Composition and Food Form Affect Glucose and Insulin Responses in Humans

Glycaemic index (GI) is used as an indicator to guide consumers in making healthier food choices. We compared the GI, insulin index (II), and the area under the curve for blood glucose and insulin as glucose (GR) and insulin responses (IR) of a newly developed liquid nutritional formula with one commercially available liquid product with different types of carbohydrates. We then evaluated the glucose and insulin responses of two test foods with comparable energy density and protein percentage but presented in different food forms (liquid vs. solid). Fourteen healthy women participated in the study. GI, II, GR, and IR were assessed after (independent) consumption of two liquid products and a solid breakfast meal. The two liquid foods showed comparable GI, whilst the liquid form appeared to produce lower median GI (25 vs. 54), and II (52 vs. 98) values compared to the solid breakfast (p < 0.02). The median GR and IR for solid breakfast were respectively 44% and 45% higher compared to the liquid product (p < 0.02). Liquid formulas with different carbohydrate qualities produced comparable glucose responses, while foods with comparable energy density and protein percentage but different food form elicited differential effects on GI, II, GR, and IR. Nutrient quality and food form need to be taken into consideration when developing low GI products to manage glycaemic responses.

Low glycaemic index diets for the prevention of cardiovascular disease

BACKGROUND

The glycaemic index (GI) is a physiological measure of the ability of a carbohydrate to affect blood glucose. Interest is growing in this area for the clinical management of people at risk of, or with, established cardiovascular disease. There is a need to review the current evidence from randomised controlled trials (RCTs) in this area. This is an update of the original review published in 2008.

OBJECTIVES

To assess the effect of the dietary GI on total mortality, cardiovascular events, and cardiovascular risk factors (blood lipids, blood pressure) in healthy people or people who have established cardiovascular disease or related risk factors, using all eligible randomised controlled trials.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase and CINAHL in July 2016. We also checked reference lists of relevant articles. No language restrictions were applied.

SELECTION CRITERIA

We selected RCTs that assessed the effects of low GI diets compared to diets with a similar composition but a higher GI on cardiovascular disease and related risk factors. Minimum trial duration was 12 weeks. Participants included were healthy adults or those at increased risk of cardiovascular disease, or previously diagnosed with cardiovascular disease. Studies in people with diabetes mellitus were excluded.

DATA COLLECTION AND ANALYSIS

Two reviewers independently screened and selected studies. Two review authors independently assessed risk of bias, evaluated the overall quality of the evidence using GRADE, and extracted data following the Cochrane Handbook for Systematic Reviews of Interventions. We contacted trial authors for additional information. Analyses were checked by a second reviewer. Continuous outcomes were synthesized using mean differences and adverse events were synthesized narratively.

MAIN RESULTS

Twenty-one RCTs were included, with a total of 2538 participants randomised to low GI intervention (1288) or high GI (1250). All 21 included studies reported the effect of low GI diets on risk factors for cardiovascular disease, including blood lipids and blood pressure.Twenty RCTs (18 of which were newly included in this version of the review) included primary prevention populations (healthy individuals or those at high risk of CVD, with mean age range from 19 to 69 years) and one RCT was in those diagnosed with pre-existing CVD (a secondary prevention population, with mean age 26.9 years). Most of the studies did not have an intervention duration of longer than six months. Difference in GI intake between comparison groups varied widely from 0.6 to 42.None of the included studies reported the effect of low GI dietary intake on cardiovascular mortality and cardiovascular events such as fatal and nonfatal myocardial infarction, unstable angina, coronary artery bypass graft surgery, percutaneous transluminal coronary angioplasty, and stroke. The unclear risk of bias of most of the included studies makes overall interpretation of the data difficult. Only two of the included studies (38 participants) reported on adverse effects and did not observe any harms (low-quality evidence).

AUTHORS' CONCLUSIONS

There is currently no evidence available regarding the effect of low GI diets on cardiovascular disease events. Moreover, there is currently no convincing evidence that low GI diets have a clear beneficial effect on blood lipids or blood pressure parameters.

Glycaemic index and glycaemic load values of commonly consumed foods in the United Arab Emirates

Glycaemic index (GI) and glycaemic load (GL) values of some commonly consumed foods in the United Arab Emirates were determined with an aim of adding these values to the existing international table of GI and GL values. In all, eighteen test foods categorised into breads (n 5), entrée dishes (n 3), main dishes (n 5) and sweet dishes (n 5) were tested. For each test food, at least fifteen healthy participants consumed 25 or 50 g available carbohydrate portions of a reference food (glucose), which was tested three times, and a test food after an overnight fast, was tested once, on separate occasions. Capillary blood samples were obtained by finger-prick and blood glucose was measured using clinical chemistry analyser. A fasting blood sample was obtained at baseline and before consumption of test foods. Additional blood samples were obtained at 15, 30, 45, 60, 90 and 120 min after the consumption of each test food. The GI value of each test food was calculated as the percentage of the incremental area under the blood glucose curve (IAUC) for the test food of each participant divided by the average IAUC for the reference food of the same participant. The GI values of tested foods ranged from low (55 or less) to high (70 or more). The GI values of various breads and rice-containing dishes were comparable with previously published values. This study provides GI and GL values of previously untested traditional Emirati foods which could provide a useful guide on dietary recommendations for the Emirati population.

The effects of meal glycemic load on blood glucose levels of adults with different body mass indexes

AIMS

The aim was to determine the effect of meal glycemic load (GL) on blood glucose levels of healthy people with different body mass indexes (BMIs).

METHODS

Thirty healthy controls were included in this study. The participants were divided into two groups according to their BMI as normal group (BMI = 18.5-24.9 kg/m², n = 15) and overweight group (BMI = 25.0-29.9 kg/m², n = 15). Dietary assessment was done by the 24-h recall method for 3 successive days. Cases were fed by breakfasts with two different GL on consecutive days. Energy values of the test meal, adjusted to meet 25% of daily energy requirements of each case, were identical in low and high GL meal (483 kcal and 482 kcal, respectively). Finger-prick capillary blood samples were taken on 0, 15, 30, 45, 60, 90, and 120 min.

RESULTS

Average daily energy intake in normal and overweight group was found as 2514.3 ± 223.8 kcal, 2064.1 ± 521.6 kcal and 2211.4 ± 368.7 kcal, 2494.8 ± 918 kcal in males and females, respectively. Blood glucose level was increased and remained more stable in both high GL meal groups compared to low (P < 0.05). The effects of GL on BMI classified groups were also found different. High GL meal was found to be more effective for increasing blood glucose level, especially on overweight group (P < 0.05).

CONCLUSIONS

The effects of GL meal were found to be different on normal and overweight individuals. The high GL meals were more effective to increase the blood glucose level than low GL meal, especially on overweight people.

Glycemic indices, glycemic load and glycemic response for seventeen varieties of dates grown in Saudi Arabia

BACKGROUND

Dates are consumed worldwide, and are an important fruit for many individuals in Saudi Arabia. Currently, limited information is available on the glycemic indices of different date varieties.

OBJECTIVES

To determine the glycemic index (GI), glycemic load (GL) and glycemic response for 17 common date varieties in Saudi Arabia.

DESIGN

Prospective clinical trial on healthy subjects.

SETTING

College of Medicine, Qassim University, Buraydah, Saudi Arabia.

PATIENTS AND METHODS

The available carbohydrate content of Tamer stage dates was determined using standard laboratory methods. Healthy subjects (ten males and nine females) received 50 g of glucose (on three separate occasions) and 50 g equivalent of available carbohydrates from the seventeen varieties of date (each once). The GI and GL were then calculated.

MAIN OUTCOME MEASURE(S)

GI, GL, and glycemic response.

RESULTS

The mean (SEM) GI of the date samples was 55.2 (7.7) (range, 42.8-74.6). Sellaj and Maktoomi exhibited the highest GI (74.6 [10.1] and 71.0 [11.1]), respectively, whereas Shaqra, Sukkary, and Sag'ai had the lowest GI (42.8 [5.5], 43.4 [4.7] and 44.6 [6]), respectively. The GL of the date samples ranged from 8.5 to 24. Sellaj had a high GL (24), whereas Ajwah and Shaqra had a low GL (8.5 and 9.2). The analyses suggested no significant difference in GI between the date varieties. However, the GL values differed significantly between the 17 date varieties (P < .001).

CONCLUSION

The results provide reliable GI and GL values for 17 common date varieties in Saudi Arabia. The identification of date varieties with lower glycemic responses may help lower the GI of the diet of both healthy and diabetic Saudi individuals.

LIMITATIONS

We used dates at the Tamer stage, which may not be translatable to all types of dates.

NUTRALYS(®) pea protein: characterization of in vitro gastric digestion and in vivo gastrointestinal peptide responses relevant to satiety

BACKGROUND

Pea protein (from Pisum sativum) is under consideration as a sustainable, satiety-inducing food ingredient.

OBJECTIVE

In the current study, pea-protein-induced physiological signals relevant to satiety were characterized in vitro via gastric digestion kinetics and in vivo by monitoring post-meal gastrointestinal hormonal responses in rats.

DESIGN

Under in vitro simulated gastric conditions, the digestion of NUTRALYS(®) pea protein was compared to that of two dairy proteins, slow-digestible casein and fast-digestible whey. In vivo, blood glucose and gastrointestinal hormonal (insulin, ghrelin, cholecystokinin [CCK], glucagon-like peptide 1 [GLP-1], and peptide YY [PYY]) responses were monitored in nine male Wistar rats following isocaloric (11 kcal) meals containing 35 energy% of either NUTRALYS(®) pea protein, whey protein, or carbohydrate (non-protein).

RESULTS

In vitro, pea protein transiently aggregated into particles, whereas casein formed a more enduring protein network and whey protein remained dissolved. Pea-protein particle size ranged from 50 to 500 µm, well below the 2 mm threshold for gastric retention in humans. In vivo, pea-protein and whey-protein meals induced comparable responses for CCK, GLP-1, and PYY, that is, the anorexigenic hormones. Pea protein induced weaker initial, but equal 3-h integrated ghrelin and insulin responses than whey protein, possibly due to the slower gastric breakdown of pea protein observed in vitro. Two hours after meals, CCK levels were more elevated in the case of protein meals compared to that of non-protein meals.

CONCLUSIONS

These results indicate that 1) pea protein transiently aggregates in the stomach and has an intermediately fast intestinal bioavailability in between that of whey and casein; 2) pea-protein- and dairy-protein-containing meals were comparably efficacious in triggering gastrointestinal satiety signals.

A preliminary study on the variability of blood glucose following meal consumption as it relates to differences in oral glucose tolerance in young adults

Insulin resistance (IR) affects the ability to maintain normal glycemia and places one at greater risk of the development of disease. The aim of this study was to assess IR via the administration of an oral glucose tolerance test (OGTT) and then determine the relationship between IR and postprandial blood glucose levels in young adults 19-24 years of age. Following a 10 hour fast, 10 men and 10 women completed an OGTT and in three subsequent weeks consumed high, medium, and low glycemic load (GL) meals in random order. Fasted and two-hour (2 h) blood glucose levels were determined. Height, weight, and waist circumference were measured and subjects completed a questionnaire recording recent weight gain, family history of diabetes, and physical fitness. Although all fasted blood glucose levels were normal, two subjects classified as impaired glucose tolerant based on 2 h OGTT values >140 mg/dL. OGTT and high glycemic load meal 2 h blood glucose levels were highly significantly correlated (p = 0.0012). Significantly higher blood glucose levels were also found in women, high BMI, low fitness, and rapid weight gain groups. Although limited by a small sample, these preliminary data suggest that glycemic response to meal ingestion is based on both the GL of the meal and the individual's level of IR.

Methodology for adding glycemic index to the National Health and Nutrition Examination Survey nutrient database

Generating valid estimates of dietary glycemic index (GI) and glycemic load (GL) has been a challenge in nutritional epidemiology. The methodologic issues may have contributed to the wide variation of GI/GL associations with health outcomes observed in existing literature. We describe a standardized methodology for assigning GI values to items in the National Health and Nutrition Examination Survey (NHANES) nutrient database using the new International Tables to develop research-driven, systematic procedures and strategies to estimate dietary GI/GL exposures of a nationally representative population sample. Nutrient databases for NHANES 2003-2006 contain information on 3,155 unique foods derived from the US Department of Agriculture National Nutrient Database for Standard Reference versions 18 and 20. Assignment of GI values were made to a subset of 2,078 carbohydrate-containing foods using systematic food item matching procedures applied to 2008 international GI tables and online data sources. Matching protocols indicated that 45.4% of foods had identical matches with existing data sources, 31.9% had similar matches, 2.5% derived GI values calculated with the formula for combination foods, 13.6% were assigned a default GI value based on low carbohydrate content, and 6.7% of GI values were based on data extrapolation. Most GI values were derived from international sources; 36.1% were from North American product information. To confirm data assignments, dietary GI and GL intakes of the NHANES 2003-2006 adult participants were estimated from two 24-hour recalls and compared with published studies. Among the 3,689 men and 4,112 women studied, mean dietary GI was 56.2 (men 56.9, women 55.5), mean dietary GL was 138.1 (men 162.1, women 116.4); the distribution of dietary GI was approximately normal. Estimates of population GI and GL compare favorably with other published literature. This methodology of adding GI values to an existing population nutrient database utilized systematic matching protocols and the latest comprehensive data sources on food composition. The database can be applied in clinical and survey research settings where there is interest in estimating individual and population dietary exposures and relating them to health outcomes.

The influence of carbohydrate quality on cardiovascular disease, the metabolic syndrome, type 2 diabetes, and obesity - an overview

There is compelling evidence that carbohydrate quality has important influences on cardiovascular disease, the metabolic syndrome, type 2 diabetes, and obesity. Cohort and interventional studies indicate that dietary fiber is an important determinant of satiation, satiety, and weight gain, and also protects against cardiovascular disease. Cohort studies have shown that vegetables and fruits protect against coronary heart disease, whereas whole grains provide protection against cardiovascular disease, type 2 diabetes, and weight gain. Dietary glycemia within the range eaten by most of the population seems not to have a significant influence on body weight, although it may influence waist circumference. There is strong evidence from interventional trials that dietary glycemia does influence insulin resistance and diabetes control. Moreover, replacing saturated fat with high-glycemic carbohydrate may increase cardiovascular risk. Soft drink consumption is a proven cause of weight gain, which may relate to the lack of satiation provided by these drinks. In large amounts, dietary fructose leads to greater adverse metabolic changes than equivalent amounts of glucose, although the extent to which fructose per se is contributing to many of the metabolic changes found in the obese, as distinct from the calories it provides, is still a matter of debate.

Impact of glycaemic index and dietary fibre on insulin sensitivity during the refeeding phase of a weight cycle in young healthy men

Previous studies suggest that a low-glycaemic index (LGI) diet may improve insulin sensitivity (IS). As IS has been shown to decrease during refeeding, we hypothesised that an LGI- v. high-GI (HGI) diet might have favourable effects during this phase. In a controlled nutritional intervention study, sixteen healthy men (aged 26·8 (SD 4·1) years, BMI 23·0 (SD 1·7) kg/m2) followed 1 week of overfeeding, 3 weeks of energy restriction and of 2 weeks refeeding at ^50% energy requirement (50% carbohydrates, 35% fat and 15% protein). During refeeding, subjects were divided into two matched groups receiving either high-fibre LGI or lower-fibre HGI foods (GI 40 v. 74, fibre intake 65 (SD 6) v. 27 (SD 4) g/d). Body weight was equally regained in both groups with refeeding (mean regain 70·5 (SD 28·0)% of loss). IS was improved by energy restriction and decreased with refeeding. The decreases in IS were greater in the HGI than in the LGIgroup (group £ time interactions for insulin, homeostasis model assessment of insulin resistance (HOMAIR), Matsuda IS index (MatsudaISI);all P,0·05). Mean interstitial glucose profiles during the day were also higher in the HGI group (DAUCHGI-LGI of continuous interstitial glucose monitoring: 6·6 mmol/l per 14 h, P¼0·04). At the end of refeeding, parameters of IS did not differ from baseline values in either diet group (adiponectin, insulin, HOMAIR, Matsuda ISI, M-value; all P.0·05). In conclusion, nutritional stress imposed by dietary restriction and refeeding reveals a GI/fibre effect in healthy non-obese subjects. LGI foods rich in fibre may improve glucose metabolism during the vulnerable refeeding phase of a weight cycle.

Short-term effect of macronutrient composition and glycemic index of a yoghurt breakfast on satiety and mood in healthy young men

BACKGROUND

Promoting satiety and repressing appetite is one major goal in the dietetic therapy of obesity. In the past, several studies investigated the effect of different macronutrients, especially protein and carbohydrates, on short- and long-term satiety in humans. This paper aims to directly compare the effect of protein, rolled oats (low glycemic index), sugar or cornflakes (high glycemic index), and walnuts (high amount of omega-3 fatty acids) as ingredients of a yoghurt breakfast on short-term hunger and satiety in one setting. A second objective was to study the effect of these yoghurt breakfasts on mental state.

METHODS

14 healthy male volunteers participated in this randomized, controlled, cross-over design study. After consuming the different test meals, volunteers repeatedly completed 2 questionnaires over a total of 3 h.

RESULTS

The protein meal showed the highest satiety scores and the controls (low-calorie yoghurt) the lowest. The other test meals were not different among each other. Regarding mental state (mood, fatigue, and calmness), no significant difference between the test meals and the low-calorie control was observed.

CONCLUSION

The glycemic index does not seem to modify satiety in this short-term setting. The similar mental state between low- and high-calorie breakfasts deserves further investigations.

Impact of postprandial glycaemia on health and prevention of disease

Postprandial glucose, together with related hyperinsulinemia and lipidaemia, has been implicated in the development of chronic metabolic diseases like obesity, type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD). In this review, available evidence is discussed on postprandial glucose in relation to body weight control, the development of oxidative stress, T2DM, and CVD and in maintaining optimal exercise and cognitive performance. There is mechanistic evidence linking postprandial glycaemia or glycaemic variability to the development of these conditions or in the impairment in cognitive and exercise performance. Nevertheless, postprandial glycaemia is interrelated with many other (risk) factors as well as to fasting glucose. In many studies, meal-related glycaemic response is not sufficiently characterized, or the methodology with respect to the description of food or meal composition, or the duration of the measurement of postprandial glycaemia is limited. It is evident that more randomized controlled dietary intervention trials using effective low vs. high glucose response diets are necessary in order to draw more definite conclusions on the role of postprandial glycaemia in relation to health and disease. Also of importance is the evaluation of the potential role of the time course of postprandial glycaemia.

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.

Dietary (sensory) variety and energy balance

The prevalence of overweight and obesity in US adults is currently 68%, compared with about 47% in the early 1970s. Many dietary factors have been proposed to contribute to the US obesity epidemic, including the percentage of energy intake from fat, carbohydrate and protein; glycemic index; fruit and vegetable intake; caloric beverage intake; and fast food or other restaurant food intake. One factor that may also be important is the variety of foods in the diet having different sensory properties, that is, flavors, textures, shapes and colors. A host of studies show that when presented with a greater variety of foods within a meal, humans consume about 22% more energy compared to when only one food is available. These data are supported by laboratory animal studies on the effects of sensory variety on consumption as well as body weight and fat gain. Longer term experimental trials in humans lasting 1-2wk had mixed results but generally showed an increase in intake of 50-60kcal/d per additional food offered, provided at least 5 different foods per day were available. In only two studies to date has reducing dietary variety been explored as a potential method for weight loss. In those studies, which also incorporated a standard behavioral weight loss approach, there was no difference in weight loss when either snack food variety or low nutrient dense, high energy dense variety was limited. However, a broader treatment approach may be more effective, for example limiting the excess variety of foods high in energy density yet which provide little benefit to vitamin and mineral intake at each meal, and further studies are needed in this area.

Fiber, protein, and lupin-enriched foods: role for improving cardiovascular health

Cardiovascular diseases (CVD) are the leading cause of death globally (World Health Organisation, 2011). Many of the risk factors for CVD are modifiable, including overweight and obesity. Numerous strategies have been proposed to fight CVD, with a special focus being placed on dietary interventions for weight management. The literature suggests that two nutrients, fiber and protein, may play significant roles in weight control and hence cardiovascular health. Increasing both protein and fiber in the diet can be difficult because popular low-carbohydrate and high-protein diets tend to have considerably low-fiber intakes (Slavin, 2005). One approach to obtain both is to develop functional foods using unique ingredients. Lupin flour is a novel food ingredient derived from the endosperm of lupin. It contains 40-45% protein, 25-30% fiber, and negligible sugar and starch (Petterson and Crosbie, 1990). Research conducted to date reveals that lupin-enriched foods, which are naturally high in protein and fiber, may have a significant effect on CVD risk factors. This review explores whether there is a role for fiber-, protein-, and lupin-enriched foods in improving cardiovascular health.

Glycemic responses of patients with type 2 diabetes to individual carbohydrate-rich foods and mixed meals

AIMS

Our purpose was to determine whether the glycemic index (GI) of individual foods applies to mixed meals.

METHODS

The glycemic responses elicited by portions of 4 individual foods with 25 g of available carbohydrate when served alone (rice, lacy pancake, flatbread and noodles) and when made into typical Malaysian mixed meals (coconut milk rice, lacy pancake with chicken curry, flatbread with dhal curry and fried noodles) were measured in 10 subjects with type 2 diabetes. To allow calculation of the GI of the foods and the relative glycemic responses of the mixed meals, each subject also tested 25 g of glucose 3 times. Capillary blood glucose was measured at 30-min intervals for 180 min after consuming each test meal.

RESULTS

The mean ± SEM incremental area under the curve (AUC) after flatbread (345 ± 26 mmol × min/l) was significantly greater than after rice (238 ± 35) and lacy pancake (235 ± 31, p < 0.05), with noodles being intermediate (294 ± 35). The AUC after the flatbread with dhal curry (341 ± 49), coconut milk rice (238 ± 39) and fried noodle (272 ± 42) mixed meals were similar to those after the individual foods, but the AUC after the lacy pancake with chicken curry mixed meal (388 ± 52) was significantly greater than after the individual food item (p < 0.01).

CONCLUSIONS

The results support the utility of the GI of individual foods such as rice, flatbread and noodles when applied to mixed meals. The reason for the higher response after the lacy pancake mixed meal compared to the individual food is not clear and may warrant further research.

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.

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.

A low glycemic index diet does not affect postprandial energy metabolism but decreases postprandial insulinemia and increases fullness ratings in healthy women

At present, it is difficult to determine whether glycemic index (GI) is an important tool in the prevention of lifestyle diseases, and long-term studies investigating GI with diets matched in macronutrient composition, fiber content, energy content, and energy density are still scarce. We investigated the effects of 2 high-carbohydrate (55%) diets with low GI (LGI; 79) or high GI (HGI; 103) on postprandial blood profile, subjective appetite sensations, energy expenditure (EE), substrate oxidation rates, and ad libitum energy intake (EI) from a corresponding test meal (LGI or HGI) after consuming the diets ad libitum for 10 wk. Two groups of a total of 29 healthy, overweight women (age: 30.5 ± 6.6 y; BMI: 27.6 ± 1.5 kg/m(2)) participated in the 10-wk intervention and a subsequent 4-h meal test. The breakfast test meals differed in GI but were equal in total energy, macronutrient composition, fiber content, and energy density. The LGI meal resulted in lower plasma glucose, serum insulin, and plasma glucagon-like peptide (GLP)-1 and higher plasma glucose-dependent insulinotropic polypeptide concentrations than the HGI meal (P ≤ 0.05). Ratings of fullness were slightly higher and the desire to eat something fatty was lower after the test meal in the LGI group (P < 0.05). Postprandial plasma GLP-2, plasma glucagon, serum leptin, plasma ghrelin, EE, substrate oxidation rates, and ad libitum EI at lunch did not differ between groups. In conclusion, postprandial glycemia, insulinemia, and subjective appetite ratings after a test meal were better after 10-wk ad libitum intake of a LGI compared to a HGI diet. EE and substrate oxidation rates were, however, not affected. These findings give some support to recommendations to consume a LGI diet.

A review of weight control strategies and their effects on the regulation of hormonal balance

The estimated prevalence of obesity in the USA is 72.5 million adults with costs attributed to obesity more than 147 billion dollars per year. Though caloric restriction has been used extensively in weight control studies, short-term success has been difficult to achieve, with long-term success of weight control being even more elusive. Therefore, novel approaches are needed to control the rates of obesity that are occurring globally. The purpose of this paper is to provide a synopsis of how exercise, sleep, psychological stress, and meal frequency and composition affect levels of ghrelin, cortisol, insulin GLP-1, and leptin and weight control. We will provide information regarding how hormones respond to various lifestyle factors which may affect appetite control, hunger, satiety, and weight control.

Prediction of postprandial glycemia and insulinemia in lean, young, healthy adults: glycemic load compared with carbohydrate content alone

BACKGROUND

Dietary glycemic load (GL; defined as the mathematical product of the glycemic index and carbohydrate content) is increasingly used in nutritional epidemiology. Its ability to predict postprandial glycemia and insulinemia for a wide range of foods or mixed meals is unclear.

OBJECTIVE

Our objective was to assess the degree of association between calculated GL and observed glucose and insulin responses in healthy subjects consuming isoenergetic portions of single foods and mixed meals.

DESIGN

In study 1, groups of healthy subjects consumed 1000-kJ portions of 121 single foods in 10 food categories. In study 2, healthy subjects consumed 2000-kJ servings of 13 mixed meals. Foods and meals varied widely in macronutrient content, fiber, and GL. Glycemia and insulinemia were quantified as area under the curve relative to a reference food (= 100).

RESULTS

Among the single foods, GL was a more powerful predictor of postprandial glycemia and insulinemia than was the available carbohydrate content, explaining 85% and 59% of the observed variation, respectively (P < 0.001). Similarly, for mixed meals, GL was also the strongest predictor of postprandial glucose and insulin responses, explaining 58% (P = 0.003) and 46% (P = 0.01) of the variation, respectively. Carbohydrate content alone predicted the glucose and insulin responses to single foods (P < 0.001) but not to mixed meals.

CONCLUSION

These findings provide the first large-scale, systematic evidence of the physiologic validity and superiority of dietary GL over carbohydrate content alone to estimate postprandial glycemia and insulin demand in healthy individuals. This trial was registered at ANZCTR.org as ACTRN12610000484044.

Influence of two breakfast meals differing in glycemic load on satiety, hunger, and energy intake in preschool children

Background

Glycemic load (GL) is the product of glycemic index of a food and amount of available carbohydrate in that food divided by 100. GL represents quality and quantity of dietary carbohydrate. Little is known about the role of GL in hunger, satiety, and food intake in preschool children. The aim of this study was to investigate the effect of two breakfast meals differing in GL on hunger, satiety, and subsequent food intake at lunch in preschool children aged 4-6 y.

Methods

Twenty three subjects consumed low-GL (LGL) and high-GL (HGL) breakfast meals according to a randomized crossover design followed by an ad libitum lunch 4 h after consumption of breakfast. Children were asked to consume meals until they are full. Each treatment was repeated twice in non-consecutive days and data were averaged.

Results

Children in LGL group consumed significantly lower amounts of GL, total carbohydrate, energy, energy density, and dietary fiber and higher amounts of protein and fat at the breakfast compared to those in HGL group. Prior to lunch, children were hungrier in the HGL intervention group compared to the LGL intervention group (P < 0.03). However, no significant difference was observed between LGL and HGL intervention groups in the amount of food and energy consumed during lunch.

Conclusions

Decreased hunger in children prior to lunch in LGL group is likely due to higher protein and fat content of LGL breakfast. Diets that are low in GL can be recommended as part of healthy diet for preschool children.

Hyperphagia induced by sucrose: relation to circulating and CSF glucose and corticosterone and orexigenic peptides in the arcuate nucleus

Sucrose-rich diets compared to starch-rich diets are known to stimulate overeating under chronic conditions. The present study in normal-weight rats established an acute "preload-to-test meal" paradigm for demonstrating sucrose-induced hyperphagia and investigating possible mechanisms that mediate this behavioral phenomenon. In this acute paradigm, the rats were first given a small (15 kcal) sucrose preload (30% sucrose) for 30 min compared to an equicaloric, starch preload (25% starch with 5% sucrose) and then allowed to freely consume a subsequent test meal of lab chow. The sucrose preload, when compared to a starch preload equal in energy density and palatability, consistently increased food intake in the subsequent test meal occurring between 60 and 120 min after the end of the preload. Measurements of hormones, metabolites and hypothalamic peptides immediately preceding this hyperphagia revealed marked differences between the sucrose vs starch groups that could contribute to the increase in food intake. Whereas the sucrose group compared to the starch group immediately after the preload (at 10 min) had elevated levels of glucose in serum and cerebrospinal fluid (CSF) along with reduced expressions of neuropeptide Y (NPY) and agouti-related protein (AgRP) in the arcuate nucleus (ARC), the subsequent effects (at 30-60 min) just preceding the test meal hyperphagia were the reverse. Along with lower levels of glucose, they included markedly elevated serum and CSF levels of corticosterone and mRNA levels of NPY and AgRP in the ARC. In addition to establishing an animal model for sucrose-induced hyperphagia, these results demonstrate peripheral and central mechanisms that may mediate this behavioral phenomenon.

Effect of carbohydrate digestibility on appetite and its relationship to postprandial blood glucose and insulin levels

BACKGROUND/OBJECTIVES

'Slowly digestible' carbohydrates have been claimed to reduce appetite through their effects on postprandial glucose and insulin levels, but literature is inconsistent. The inconsistencies between studies might be explained by factors other than glycemic effects per se, for example, nutritional or physical properties. We tested this possibility by examining postprandial glucose, insulin and appetite responses to drinks differing only in rate and extent of digestibility of carbohydrates. This was accomplished by comparing different glucose polymers: maltodextrin (rapidly digestible) versus medium-chain pullulan (slowly but completely digestible) versus long-chain pullulan (indigestible).

SUBJECTS/METHODS

In a randomized double-blind balanced crossover design, 35 subjects received drinks with 15 g test carbohydrate polymers. Key outcome measures were appetite scores, digestibility (in vitro test and breath hydrogen), and (in a subset) glucose and insulin levels.

RESULTS

Digestibility, glucose and insulin data confirmed the rapid, slow and nondigestible nature of the test carbohydrates. Despite its low digestibility, only long-chain pullulan reduced appetite compared with the maltodextrin control, whereas the medium-chain pullulan did not.

CONCLUSIONS

We conclude that glycemic responses per se have minimal effects on appetite, when tested in products differing in only carbohydrate digestibility rate and extent.

Chemical composition and glycemic index of three varieties of Omani dates

The present study evaluated the nutritional quality and glycemic index of three sun-dried date varieties (Khalas, Khsab and Fardh) grown in Oman. Significant (P<0.05) differences were observed in the proximate chemical composition, dietary fiber contents, various sugar fractions and energy value of these dates. The moisture, ash, crude protein, total fat, and nitrogen-free extract values ranged between 18.77 and 23.71 g/100 g date flesh, 1.12 and 1.55 g/100 g date flesh, 1.28 and 1.89 g/100 g date flesh, 1.14 and 2.37 g/100 g date flesh, and 68.53 and 75.37 g/100 g date flesh, respectively. The dietary fiber and total sugar contents ranged between 8.83 and 13.11 g/100 g and between 52.17 and 59.96 g/100 g, respectively. The glycemic index (GI) of different varieties of dates collected from various regions of Oman ranged between 47.6 and 57.7. Overall no significant (P<0.05) differences were observed in the GI values of different varieties of dates. The regional effects on the GI values of dates were also non-significant (P>0.05). An inverse correlation (r(2)) was observed between the fructose fraction and the GI value of dates.

Effect of dietary glycemic index on food intake, adiposity, and fasting plasma ghrelin levels in animals

BACKGROUND

An increase in lipid storage as a consequence of feeding animals with high-glycemic index (GI) diets has been observed by many authors. Ghrelin is one of the most important orexigenic hormones, and curiously, its fasting plasma levels are decreased in human obesity.

AIM

As ghrelin secretion is affected by insulin concentration, we hypothesized that carbohydrates with different glycemic responses might influence fasting plasma ghrelin levels.

MATERIAL AND METHODS

Twenty rats were divided into two groups and fed ad libitum a low-GI or a high-GI diet for 21 days.

RESULTS

In rats fed a high- vs low-GI diet we observed: increased food intake (18.9+/-0.6 vs 16.4+/-2.0 g/day; p<0.01), increased weight gain (28.8+/-6.6 vs 16.4+/-6% of initial weight; p<0.01), higher relative weight of epididymal fat pads (1.7+/-0.4 vs 1.4+/-0.3%; p=0.05), but lower total fasting ghrelin levels (41.1+/-10.7 vs 59.5+/-9.8 pg/ml; p=0.05).

CONCLUSIONS

Ghrelin appeared to be downregulated in rats fed a high-GI diet; this observation could be related to the higher food intake and fat mass observed in these rats and to the effects of insulin response on ghrelin levels.

Diet and acne

Historically, the relationship between diet and acne has been highly controversial. Before the 1960s, certain foods were thought to exacerbate acne. However, subsequent studies dispelled these alleged associations as myth for almost half a century. Several studies during the last decade have prompted dermatologists to revisit the potential link between diet and acne. This article critically reviews the literature and discusses how dermatologists might address diet when counseling patients with acne. Dermatologists can no longer dismiss the association between diet and acne. Compelling evidence exists that high glycemic load diets may exacerbate acne. Dairy ingestion appears to be weakly associated with acne, and the roles of omega-3 fatty acids, antioxidants, zinc, vitamin A, and dietary fiber remain to be elucidated. This study was limited by the lack of randomized controlled trials in the literature. We hope that this review will encourage others to explore the effects of diet on acne.

Appetite control: methodological aspects of the evaluation of foods

This report describes a set of scientific procedures used to assess the impact of foods and food ingredients on the expression of appetite (psychological and behavioural). An overarching priority has been to enable potential evaluators of health claims about foods to identify justified claims and to exclude claims that are not supported by scientific evidence for the effect cited. This priority follows precisely from the principles set down in the PASSCLAIM report. The report allows the evaluation of the strength of health claims, about the effects of foods on appetite, which can be sustained on the basis of the commonly used scientific designs and experimental procedures. The report includes different designs for assessing effects on satiation as opposed to satiety, detailed coverage of the extent to which a change in hunger can stand alone as a measure of appetite control and an extensive discussion of the statistical procedures appropriate for handling data in this field of research. Because research in this area is continually evolving, new improved methodologies may emerge over time and will need to be incorporated into the framework. One main objective of the report has been to produce guidance on good practice in carrying out appetite research, and not to set down a series of commandments that must be followed.

Nutritional treatment of obesity

The focus of this article is nutritional strategies for weight loss. Following a review of general nutritional principles, the evidence behind specific nutritional weight-loss strategies is presented. These strategies include nutritional supplements, nutrient-limited diets, and energy-limited diets. A brief discussion of nutritional considerations relevant to other weight-loss strategies--pharmacologic, surgical, and exercise-based--is included. Specific evidence-based recommendations are presented.