A novel interaction between dietary composition and insulin secretion: effects on weight gain in the Quebec Family Study

Future cardiometabolic implications of insulin hypersecretion in response to oral glucose: a prospective cohort study

Background

The cardiometabolic implications of postprandial hyperinsulinemia are unclear with recent studies suggesting both adverse and beneficial associations. We aimed to evaluate the longitudinal cardiometabolic implications of the post-challenge insulin secretory response over 4-years follow-up.

Methods

In this prospective cohort study, conducted in Toronto (Ontario, Canada), women comprising the full range of antepartum glucose tolerance were recruited in pregnancy (at the time of glucose tolerance screening, late in the second trimester) to undergo cardiometabolic testing in the years thereafter. Participants underwent oral glucose tolerance tests (OGTT) at 1-year, 3-years, and 5-years postpartum, enabling serial assessment of cardiovascular risk factors, glucose tolerance, insulin sensitivity or resistance (Matsuda index, HOMA-IR), and beta-cell function-via Insulin Secretion-Sensitivity Index-2 (ISSI-2) and insulinogenic index/HOMA-IR (IGI/HOMA-IR). Baseline post-challenge insulinemia was assessed with the corrected insulin response (CIR) at 1-year. Cardiometabolic factors were compared between baseline CIR tertiles.

Findings

Between Oct 23, 2003 and March 31, 2014, 306 women were enrolled. In this study population, there was progressive worsening of waist circumference (p = 0.016), HDL (p = 0.018), CRP (p = 0.006), and insulin sensitivity (p < 0.001) from the lowest to middle to highest tertile of CIR at 1-year. However, these adverse features were accompanied by progressively better beta-cell function (both p < 0.001), coupled with lower fasting and 2-h glucose on the OGTT (both p < 0.001). On adjusted longitudinal analyses, higher CIR tertile at 1-year was independently associated with (i) higher ISSI-2 and IGI/HOMA-IR and (ii) lower fasting and 2-h glucose at both 3-years and 5-years (all p < 0.001), but was not associated with BMI, waist, lipids, CRP or insulin sensitivity/resistance. The highest CIR tertile at 1-year predicted lower risk of pre-diabetes or diabetes at both 3-years (adjusted OR = 0.19; 95% CI 0.08-0.45) and 5-years (aOR = 0.18; 0.08-0.39), relative to the lowest tertile.

Interpretation

A robust post-challenge insulin secretory response does not indicate adverse cardiometabolic health but, rather, portends favourable metabolic function in the years to come. Future long-term study of the implications of the post-challenge insulinemic response is warranted.

Funding

Canadian Institutes of Health Research.

Prevalence and Risk Factors of Comorbid Obesity in Chinese Patients with Bipolar Disorder

Purpose

Bipolar disorder (BD) predisposes patients to comorbid obesity and increases the risk of metabolic syndrome and cardiovascular disease. In this study, we investigated the prevalence of comorbid obesity and its risk factors in patients with BD in China.

Patients and Methods

We conducted a cross-sectional retrospective survey of 642 patients with BD. Demographic data were collected, physical examinations were performed, and biochemical indexes, including fasting blood glucose, alanine aminotransferase (ALT), aspartate aminotransferase, and triglycerides (TG) levels, were measured. Height and weight were measured on an electronic scale at admission, and body mass index (BMI) was in kg/m². Pearson's correlation analysis was used to analyze the correlation between BMI and variable indicators. Multiple linear regression analysis was used to analyze the risk factors for comorbid obesity in patients with BD.

Results

The prevalence of comorbid obesity in Chinese patients with BD was 21.3%. Obese patients had high levels of blood glucose, ALT, glutamyl transferase, cholesterol, apolipoprotein B (Apo B), TG, and uric acid in the plasma; however, the levels of high-density lipoprotein and apolipoprotein A1 were lower than those in non-obese patients. Partial correlation analysis showed that BMI was associated with ApoB, TG, uric acid, blood glucose, GGT, TC, ApoA1, HDL, and ALT levels. Multiple linear regression showed that ALT, blood glucose, uric acid, TG, and Apo B levels were important risk factors of BMI.

Conclusion

The prevalence of obesity is higher in patients with BD in China, and TG, blood glucose, liver enzymes, and uric acid are closely related to obesity. Therefore, more attention should be paid to patients with comorbid obesity. Patients should be encouraged to increase their physical activity, control sugar and fat intake, and reduce the prevalence of comorbid obesity and risk of serious complications.

Interactions of dietary insulin index and dietary insulin load with brain-derived neurotrophic factor (BDNF) Val66Met polymorphism in relation to cardiometabolic markers in Iranian diabetic patients: a cross-sectional study

The progression of cardiometabolic diseases is determined by both genetic and environmental factors. Gene-diet interactions may therefore be important in modulating the risks of developing metabolic diseases. The objectives were to investigate the effect of the interaction between brain-derived neurotrophic factor (BDNF) Val66Met polymorphisms and dietary insulin index (DII) and dietary insulin load (DIL) on cardiometabolic markers among diabetic patients. In this cross-sectional study, blood samples were collected from 667 patients. DIL and DII were defined using a validated FFQ. Genotyping the BDNF Val66Met polymorphism was conducted by the PCR-Restriction fragment length polymorphism (RFLP) method. Interactions between dietary indices and gene variants were evaluated using a generalised linear model. PGF2a concentrations were significantly higher among Val homozygotes than Met-allele carrier. This study revealed that, compared with individuals with the Val/Val genotype, those with the Met/Val or Met/Met genotype had lower BMI (P_interaction = 0·04), TAG (P_interaction = 0·04), leptin (P_interaction = 0·01), LDL (P_interaction = 0·04) and total cholesterol (P_interaction = 0·01) when they consumed diets higher on the DIL index. Moreover, the highest quartile of the DIL, compared with the lowest, showed increase in waist circumference (P_interaction = 0·02) and LDL/HDL (P_interaction = 0·04) for Val/Val homozygotes compared with Met-allele carriers. BDNF Val66Met variants may interact with DIL and DII, thus be involved in the development of cardiometabolic risk factors. If diabetic patients with Met alleles regulate dietary intakes, they have a protective opportunity to regulate their cardiometabolic markers.

Lack of Evidence for a Causal Role of Hyperinsulinemia in the Progression of Obesity in Children and Adolescents: A Longitudinal Study

OBJECTIVE

The carbohydrate-insulin model (CIM) claims that chronic exposure to hyperinsulinemia induced by dietary carbohydrates explains development of obesity via direct effects of insulin and/or low postprandial metabolic fuel levels. We aimed at testing whether indices of hyperinsulinemia and postprandial glucose levels can predict increases in the degree of obesity over time.

RESEARCH DESIGN AND METHODS

Children and adolescents with obesity attending a pediatric obesity clinic performed oral glucose tolerance tests (OGTTs) and received standard obesity management. Indices of hyperinsulinemia and insulin secretion were derived from the OGTT and evaluated in the face of changes in the degree of obesity over time.

RESULTS

A total of 591 children (217 males and 374 females) participated, and the mean follow-up was 1.86 ± 1.29 years. OGTT-derived area under the curve of insulin, peak insulin, fasting insulin, the insulinogenic index, or insulin at 30 min were not associated with greater changes in the degree of obesity in univariate or multivariate analyses (adjusted for baseline age, BMI z score, sex, and ethnicity). Low postprandial glucose <75 mg/dL was not associated with greater changes in the degree of obesity in univariate or multivariate analyses. In a subsample of 104 participants with a follow-up >4 years, none of these parameters was associated with greater increases in the degree of obesity.

CONCLUSIONS

In children and adolescents with obesity, exposure to hyperinsulinemia, greater insulin secretion, or low postprandial glucose is not associated with greater increases in the degree of obesity over 2-4 years. The CIM should be evaluated in children with lower BMI and for longer follow-up periods.

A Personalized Diet Approach Study: Interaction between PPAR-γ Pro12Ala and Dietary Insulin Indices on Metabolic Markers in Diabetic Patients

BACKGROUND

The objectives were to investigate the effect of the interaction between peroxisome proliferator-activated receptor gamma (PPAR-γ) Pro12Ala polymorphisms and dietary insulin load and insulin index (DIL and DII) on Cardio-metabolic Markers among diabetic patients.

METHODS

This cross-sectional study was conducted on 393 diabetic patients. Food-frequency questionnaire (FFQ) was used for DIL and DII calculation. PPAR-γ Pro12Ala was genotyped by the PCR-RFLP method. Biochemical markers including TC, LDL, HDL, TG, SOD, CRP, TAC, PTX3, PGF2α. IL18, leptin and ghrelin were measured by standard protocol.

RESULT

Risk-allele carriers (CG, GG) had higher obesity indices WC (P _interaction =0.04), BMI (P _interaction =0.006) and, WC (P _interaction =0.04) compared with individuals with the CC genotype when they consumed a diet with higher DIL and DII respectively. Besides, carriers of the G allele who were in the highest tertile of DIL, had lower HDL (P _interaction =0.04) and higher PGF2α (P _interaction =0.03) and PTX3 (P _interaction =0.03). Moreover, the highest tertile of the DII, showed an increase in IL18 (P _interaction =0.01) and lower SOD (P _interaction =0.03) for risk allele carriers compared to those with CC homozygotes.

CONCLUSION

We revealed PPAR-γ Pro12Ala polymorphism was able to intensify the effect of DIL and DII on CVD risk factors; risk-allele carriers who consumed a diet with high DIL and DII score have more likely to be obese and have higher inflammatory markers. Also, protective factor against CVD risk factors were reduced significantly in this group compared to CC homozygotes. This article is protected by copyright. All rights reserved.

Stimulated Insulin Secretion Predicts Changes in Body Composition Following Weight Loss in Adults with High BMI

BACKGROUND

The aim of obesity treatment is to promote loss of fat relative to lean mass. However, body composition changes with calorie restriction differ among individuals.

OBJECTIVES

The goal of this study was to test the hypothesis that insulin secretion predicts body composition changes among young and middle-age adults with high BMI (in kg/m2) following major weight loss.

METHODS

Exploratory analyses were conducted with pre-randomization data from 2 large feeding trials: the Framingham, Boston, Bloomington, Birmingham, and Baylor study (FB4; n = 82, 43.9% women, BMI ≥27) and the Framingham State Food Study [(FS)2; n = 161, 69.6% women, BMI ≥25]. Participants in the 2 trials consumed calorie-restricted moderate-carbohydrate or very-low-carbohydrate diets to produce 12-18% weight loss in ∼14 wk or 10-14% in ∼10 wk, respectively. We determined insulin concentration 30 min after a 75-g oral glucose load (insulin-30) as a measure of insulin secretion and HOMA-IR as a measure of insulin resistance at baseline. Body composition was determined by DXA at baseline and post-weight loss. Associations were analyzed using general linear models with adjustment for covariates.

RESULTS

In FB4, higher insulin-30 was associated with a smaller decrease in fat mass (0.441 kg per 100 μIU/mL increment in baseline insulin-30; P = 0.005; -1.20-kg mean difference between the first compared with the fifth group of insulin-30) and a larger decrease in lean mass (-0.465 kg per 100 μIU/mL; P = 0.004; 1.27-kg difference). Participants with higher insulin-30 lost a smaller proportion of weight loss as fat (-3.37% per 100 μIU/mL; P = 0.003; 9.20% difference). Greater HOMA-IR was also significantly associated with adverse body composition changes. Results from (FS)2 were qualitatively similar but of a smaller magnitude.

CONCLUSIONS

Baseline insulin dynamics predict substantial individual differences in body composition following weight loss. These findings may inform understanding of the pathophysiological basis for weight regain and the design of more effective obesity treatment. Registered at clinicaltrials.gov as NCT03394664 and NCT02068885.

The carbohydrate-insulin model: a physiological perspective on the obesity pandemic

According to a commonly held view, the obesity pandemic is caused by overconsumption of modern, highly palatable, energy-dense processed foods, exacerbated by a sedentary lifestyle. However, obesity rates remain at historic highs, despite a persistent focus on eating less and moving more, as guided by the energy balance model (EBM). This public health failure may arise from a fundamental limitation of the EBM itself. Conceptualizing obesity as a disorder of energy balance restates a principle of physics without considering the biological mechanisms that promote weight gain. An alternative paradigm, the carbohydrate-insulin model (CIM), proposes a reversal of causal direction. According to the CIM, increasing fat deposition in the body-resulting from the hormonal responses to a high-glycemic-load diet-drives positive energy balance. The CIM provides a conceptual framework with testable hypotheses for how various modifiable factors influence energy balance and fat storage. Rigorous research is needed to compare the validity of these 2 models, which have substantially different implications for obesity management, and to generate new models that best encompass the evidence.

Improving nutrition for the prevention of gestational diabetes: Current status and perspectives

Gestational diabetes mellitus (GDM) is a common complication of pregnancy and a serious public health problem. It carries significant risks of short-term and long-term adverse health effects for both mothers and their children. Risk factors, especially modifiable risk factors, must be considered to prevent GDM and its consequences. Observational studies have identified several nutritional and lifestyle factors associated with the risk of GDM. The results of intervention studies examining the effects of diet and lifestyle on the prevention of GDM are contradictory. Differences in the study populations, types and intensity of intervention, time frame of the intervention, and diagnostic criteria for GDM may explain the heterogeneity in the results of intervention studies. This review provides an overview of new diets and other factors that may help prevent GDM. The main results of epidemiological studies assessing the risk factors for GDM, as well as the results and methodological problems of intervention studies on the prevention of GDM and their meta-analyses, are discussed. In addition, the evidence that gene and lifestyle interactions influence the development of GDM, as well as prospects for increasing the effectiveness of interventions designed to prevent GDM, including new data on the possible uses of personalized diet therapy, are highlighted.

Diets Varying in Carbohydrate Content Differentially Alter Brain Activity in Homeostatic and Reward Regions in Adults

BACKGROUND

Obesity has one of the highest refractory rates of all chronic diseases, in part because weight loss induced by calorie restriction, the first-line treatment for obesity, elicits biological adaptations that promote weight regain. Although acute feeding trials suggest a role for macronutrient composition in modifying brain activity related to hunger and satiety, relevance of these findings to weight-loss maintenance has not been studied.

OBJECTIVES

We investigated effects of weight-loss maintenance diets varying in macronutrient content on regional cerebral blood flow (rCBF) in brain regions involved in hunger and reward.

METHODS

In conjunction with a randomized controlled feeding trial, we investigated the effects of weight-loss maintenance diets varying in carbohydrate content [high, 60% of total energy: n = 20; 6 men/14 women; mean age: 32.5 y; mean BMI (in kg/m 2): 27.4; moderate, 40% of total energy: n = 22; 10 men/12 women; mean age: 32.5 y; mean BMI: 29.0; low, 20% of total energy: n = 28; 12 men/16 women; mean age: 33.2 y; mean BMI: 27.7] on rCBF in brain regions involved in hunger and reward preprandial and 4 h postprandial after 14-20 wk on the diets. The primary outcome was rCBF in the nucleus accumbens (NAcc) at 4 h postprandial; the secondary outcome was preprandial rCBF in the hypothalamus.

RESULTS

Consistent with a priori hypothesis, at 4 h postprandial, NAcc rCBF was 43% higher in adults assigned to the high- compared with low-carbohydrate diet {P[family-wise error (FWE)-corrected] < 0.05}. Preprandial hypothalamus rCBF was 41% higher on high-carbohydrate diet [P(FWE-corrected) < 0.001]. Exploratory analyses revealed that elevated rCBF on high-carbohydrate diet was not specific to prandial state: preprandial NAcc rCBF [P(FWE-corrected) < 0.001] and 4 h postprandial rCBF in hypothalamus [P(FWE-corrected) < 0.001]. Insulin secretion predicted differential postprandial activation of the NAcc by diet.

CONCLUSIONS

We report significant differences in rCBF in adults assigned to diets varying in carbohydrate content for several months, which appear to be partially associated with insulin secretion. These findings suggest that chronic intake of a high-carbohydrate diet may affect brain reward and homeostatic activity in ways that could impede weight-loss maintenance. This trial was registered at clinicaltrials.gov as NCT02300857.

[Lipids should not be demonized in adults and in infants]

Following a long and dogmatic period, which has demonized the dietary lipids, a cautious review of the literature led the scientists to propose a new paradigm and rehabilitation for lipids. French guidelines have endorsed it since 2010, and recent data confirm this new and necessary approach, especially for infants.

Do Lower-Carbohydrate Diets Increase Total Energy Expenditure? An Updated and Reanalyzed Meta-Analysis of 29 Controlled-Feeding Studies

BACKGROUND

The effect of macronutrient composition on total energy expenditure (TEE) remains controversial, with divergent findings among studies. One source of heterogeneity may be study duration, as physiological adaptation to lower carbohydrate intake may require 2 to 3 wk.

OBJECTIVE

We tested the hypothesis that the effects of carbohydrate [expressed as % of energy intake (EI)] on TEE vary with time.

METHODS

The sample included trials from a previous meta-analysis and new trials identified in a PubMed search through 9 March 2020 comparing lower- and higher-carbohydrate diets, controlled for EI or body weight. Three reviewers independently extracted data and reconciled discrepancies. Effects on TEE were pooled using inverse-variance-weighted meta-analysis, with between-study heterogeneity assessed using the I2 statistic. Meta-regression was used to quantify the influence of study duration, dichotomized at 2.5 wk.

RESULTS

The 29 trials ranged in duration from 1 to 140 d (median: 4 d) and included 617 participants. Difference in carbohydrate between intervention arms ranged from 8% to 77% EI (median: 30%). Compared with reported findings in the prior analysis (I2 = 32.2%), we found greater heterogeneity (I2 = 90.9% in the reanalysis, 81.6% in the updated analysis). Study duration modified the diet effect on TEE (P < 0.001). Among 23 shorter trials, TEE was reduced on lower-carbohydrate diets (-50.0 kcal/d; 95% CI: -77.4, -22.6 kcal/d) with substantial heterogeneity (I2 = 69.8). Among 6 longer trials, TEE was increased on low-carbohydrate diets (135.4 kcal/d; 95% CI: 72.0, 198.7 kcal/d) with low heterogeneity (I2 = 26.4). Expressed per 10% decrease in carbohydrate as %EI, the TEE effects in shorter and longer trials were -14.5 kcal/d and 50.4 kcal/d, respectively. Findings were materially unchanged in sensitivity analyses.

CONCLUSIONS

Lower-carbohydrate diets transiently reduce TEE, with a larger increase after ∼2.5 wk. These findings highlight the importance of longer trials to understand chronic macronutrient effects and suggest a mechanism whereby lower-carbohydrate diets may facilitate weight loss.

Effects of Dietary Carbohydrate Content on Circulating Metabolic Fuel Availability in the Postprandial State

Context

According to the carbohydrate-insulin model of obesity, an elevated insulin-to-glucagon ratio in response to a high-carbohydrate diet directs metabolic fuels toward storage, resulting in lower circulating energy.

Objective

To determine differences in total circulating energy post-meal related to dietary carbohydrate.

Design

Ancillary study within the Framingham State Food Study.

Setting

University community.

Participants

29 adults (aged 20 to 65 years) with overweight or obesity (body mass index ≥25 kg/m²)

Intervention

After achieving 10% to 14% weight loss on a run-in diet, participants were randomized to weight-loss-maintenance test diets varying in carbohydrate content (high-carbohydrate, 60% of total energy, n = 11; moderate-carbohydrate, 40%, n = 8; low-carbohydrate, 20%, n = 10) and controlled for protein (20%). During 24-hour metabolic ward admissions between 10 and 15 weeks on the test diets, metabolic fuels and hormones were measured.

Main Outcome Measure

Energy availability (EA) based on energy content of blood glucose, beta-hydroxybutyrate, and free fatty acids, in the late postprandial period (180 to 300 minutes). Insulin at 30 minutes into the test meal (Meal Insulin-30) was measured as an effect modifier.

Results

Insulin-to-glucagon ratio was 7-fold higher in participants on the high- vs low-carbohydrate diet (2.5 and 0.36, respectively). Late postprandial EA was 0.58 kcal/L lower on the high- vs low-carbohydrate diet (P < 0.0001), primarily related to suppression of free fatty acids. Early postprandial EA (30 to 180 minutes) declined fastest in the high-carbohydrate group, and Meal Insulin-30 modified this diet effect.

Conclusions

During weight-loss maintenance on a high-carbohydrate diet, late postprandial EA is reduced, consistent with the carbohydrate-insulin model.

Using metabolite profiling to construct and validate a metabolite risk score for predicting future weight gain

Background

Excess weight gain throughout adulthood can lead to adverse clinical outcomes and are influenced by complex factors that are difficult to measure in free-living individuals. Metabolite profiling offers an opportunity to systematically discover new predictors for weight gain that are relatively easy to measure compared to traditional approaches.

Methods and results

Using baseline metabolite profiling data of middle-aged individuals from the Framingham Heart Study (FHS; n = 1,508), we identified 42 metabolites associated (p < 0.05) with longitudinal change in body mass index (BMI). We performed stepwise linear regression to select 8 of these metabolites to build a metabolite risk score (MRS) for predicting future weight gain. We replicated the MRS using data from the Mexico City Diabetes Study (MCDS; n = 768), in which one standard deviation increase in the MRS corresponded to ~0.03 increase in BMI (kg/m²) per year (i.e. ~0.09 kg/year for a 1.7 m adult). We observed that none of the available anthropometric, lifestyle, and glycemic variables fully account for the MRS prediction of weight gain. Surprisingly, we found the MRS to be strongly correlated with baseline insulin sensitivity in both cohorts and to be negatively predictive of T2D in MCDS. Genome-wide association study of the MRS identified 2 genome-wide (p < 5 × 10⁻⁸) and 5 suggestively (p < 1 × 10⁻⁶) significant loci, several of which have been previously linked to obesity-related phenotypes.

Conclusions

We have constructed and validated a generalizable MRS for future weight gain that is an independent predictor distinct from several other known risk factors. The MRS captures a composite biological picture of weight gain, perhaps hinting at the anabolic effects of preserved insulin sensitivity. Future investigation is required to assess the relationships between MRS-predicted weight gain and other obesity-related diseases.

Genetic Evidence That Carbohydrate-Stimulated Insulin Secretion Leads to Obesity

BACKGROUND

A fundamental precept of the carbohydrate-insulin model of obesity is that insulin secretion drives weight gain. However, fasting hyperinsulinemia can also be driven by obesity-induced insulin resistance. We used genetic variation to isolate and estimate the potentially causal effect of insulin secretion on body weight.

METHODS

Genetic instruments of variation of insulin secretion [assessed as insulin concentration 30 min after oral glucose (insulin-30)] were used to estimate the causal relationship between increased insulin secretion and body mass index (BMI), using bidirectional Mendelian randomization analysis of genome-wide association studies. Data sources included summary results from the largest published metaanalyses of predominantly European ancestry for insulin secretion (n = 26037) and BMI (n = 322154), as well as individual-level data from the UK Biobank (n = 138541). Data from the Cardiology and Metabolic Patient Cohort study at Massachusetts General Hospital (n = 1675) were used to validate genetic associations with insulin secretion and to test the observational association of insulin secretion and BMI.

RESULTS

Higher genetically determined insulin-30 was strongly associated with higher BMI (β = 0.098, P = 2.2 × 10^-21), consistent with a causal role in obesity. Similar positive associations were noted in sensitivity analyses using other genetic variants as instrumental variables. By contrast, higher genetically determined BMI was not associated with insulin-30.

CONCLUSIONS

Mendelian randomization analyses provide evidence for a causal relationship of glucose-stimulated insulin secretion on body weight, consistent with the carbohydrate-insulin model of obesity.

The Metabolomic Signatures of Weight Change

Obesity represents a major health concern, not just in the West but increasingly in low and middle income countries. In order to develop successful strategies for losing weight, it is essential to understand the molecular pathogenesis of weight change. A number of pathways, implicating oxidative stress but also the fundamental regulatory of insulin, have been implicated in weight gain and in the regulation of energy expenditure. In addition, a considerable body of work has highlighted the role of metabolites generated by the gut microbiome, in particular short chain fatty acids, in both processes. The current review provides a brief understanding of the mechanisms underlying the associations of weight change with changes in lipid and amino acid metabolism, energy metabolism, dietary composition and insulin dynamics, as well as the influence of the gut microbiome. The changes in metabolomic profiles and the models outlined can be used as an accurate predictor for obesity and obesity related disorders.

The rationale and design of the personal diet study, a randomized clinical trial evaluating a personalized approach to weight loss in individuals with pre-diabetes and early-stage type 2 diabetes

Weight loss reduces the risk of type 2 diabetes mellitus (T2D) in overweight and obese individuals. Although the physiological response to food varies among individuals, standard dietary interventions use a "one-size-fits-all" approach. The Personal Diet Study aims to evaluate two dietary interventions targeting weight loss in people with prediabetes and T2D: (1) a low-fat diet, and (2) a personalized diet using a machine-learning algorithm that predicts glycemic response to meals. Changes in body weight, body composition, and resting energy expenditure will be compared over a 6-month intervention period and a subsequent 6-month observation period intended to assess maintenance effects. The behavioral intervention is delivered via mobile health technology using the Social Cognitive Theory. Here, we describe the design, interventions, and methods used.

Associations between dietary insulin load with cardiovascular risk factors and inflammatory parameters in elderly men: a cross-sectional study

Given the limited research on dietary insulin load (DIL), we examined DIL in relation to cardiovascular risk factors and inflammatory biomarkers in elderly men. For the present cross-sectional study, we recruited 357 elderly men. Dietary intake was assessed using FFQ. DIL was estimated by multiplying the insulin index of each food by its energy content and frequency of consumption and then summing the final value of all food items. After adjustment for covariates, a significant positive association was observed between high DIL with fasting blood sugar (FBS) levels (OR: 7·52; 95 % CI 3·38, 16·75; P=0·0001) and high-sensitive C-reactive protein (hs-CRP) (OR: 3·03; 95 % CI 1·54, 5·94; P=0·001). However, there was no association between high DIL and BMI (OR: 1·43; 95 % CI 0·75, 2·75; P=0·27), serum TAG level (OR: 0·82; 95 % CI 0·26, 2·59; P=0·73), HDL-cholesterol (OR: 2·03; 95 % CI 0·79, 5·23; P=0·13) and fibrinogen (OR: 1·57; 95 % CI 0·80, 3·06; P=0·18). Overall, elderly men with high DIL had higher FBS and hs-CRP levels than those with low DIL. Future studies are needed to clarify the association between DIL and other cardiovascular risk factors in both men and women.

Effects of a low carbohydrate diet on energy expenditure during weight loss maintenance: randomized trial

OBJECTIVE

To determine the effects of diets varying in carbohydrate to fat ratio on total energy expenditure.

DESIGN

Randomized trial.

SETTING

Multicenter collaboration at US two sites, August 2014 to May 2017.

PARTICIPANTS

164 adults aged 18-65 years with a body mass index of 25 or more.

INTERVENTIONS

After 12% (within 2%) weight loss on a run-in diet, participants were randomly assigned to one of three test diets according to carbohydrate content (high, 60%, n=54; moderate, 40%, n=53; or low, 20%, n=57) for 20 weeks. Test diets were controlled for protein and were energy adjusted to maintain weight loss within 2 kg. To test for effect modification predicted by the carbohydrate-insulin model, the sample was divided into thirds of pre-weight loss insulin secretion (insulin concentration 30 minutes after oral glucose).

MAIN OUTCOME MEASURES

The primary outcome was total energy expenditure, measured with doubly labeled water, by intention-to-treat analysis. Per protocol analysis included participants who maintained target weight loss, potentially providing a more precise effect estimate. Secondary outcomes were resting energy expenditure, measures of physical activity, and levels of the metabolic hormones leptin and ghrelin.

RESULTS

Total energy expenditure differed by diet in the intention-to-treat analysis (n=162, P=0.002), with a linear trend of 52 kcal/d (95% confidence interval 23 to 82) for every 10% decrease in the contribution of carbohydrate to total energy intake (1 kcal=4.18 kJ=0.00418 MJ). Change in total energy expenditure was 91 kcal/d (95% confidence interval -29 to 210) greater in participants assigned to the moderate carbohydrate diet and 209 kcal/d (91 to 326) greater in those assigned to the low carbohydrate diet compared with the high carbohydrate diet. In the per protocol analysis (n=120, P<0.001), the respective differences were 131 kcal/d (-6 to 267) and 278 kcal/d (144 to 411). Among participants in the highest third of pre-weight loss insulin secretion, the difference between the low and high carbohydrate diet was 308 kcal/d in the intention-to-treat analysis and 478 kcal/d in the per protocol analysis (P<0.004). Ghrelin was significantly lower in participants assigned to the low carbohydrate diet compared with those assigned to the high carbohydrate diet (both analyses). Leptin was also significantly lower in participants assigned to the low carbohydrate diet (per protocol).

CONCLUSIONS

Consistent with the carbohydrate-insulin model, lowering dietary carbohydrate increased energy expenditure during weight loss maintenance. This metabolic effect may improve the success of obesity treatment, especially among those with high insulin secretion.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02068885.

The sliding set-point: how insulin and diet interact to explain the obesity epidemic (and how to fix it)

PURPOSE OF REVIEW

The current approach to weight loss (intentional energy deficit) is difficult to implement and sustain, and rarely leads to successful long-term weight loss maintenance. The aim of this article is to review recent literature on the role of insulin in obesity propensity, and by extension, the effectiveness of carbohydrate restriction in facilitating weight loss, with particular attention to individual variability in patient response.

RECENT FINDINGS

A genetic signature for insulin secretion predisposes to elevated BMI. A genetic signature for insulin resistance is a marker for impaired fat storage, is associated with relative leanness, and predisposes to cardiometabolic disease. The largest randomized weight-loss trial ever conducted to examine insulin/diet interactions revealed no interactive effect of insulin phenotype with diet composition on body weight in the context of energy restriction. However, smaller studies revealed unique effects of carbohydrate restriction on energy partitioning that are not reflected in body weight; that is, preferential loss of total and ectopic adipose tissue. Carbohydrate-restricted diets are associated with greater adherence, and with greater total and resting energy expenditure.

SUMMARY

For patients with a predisposition to high insulin secretion, carbohydrate restriction may facilitate long-term reductions in body fat, perhaps by reducing hunger, maintaining energy expenditure, and promoting adherence.

Personalized Dietary Management of Overweight and Obesity Based on Measures of Insulin and Glucose

During the past several decades, numerous trials have compared various diets for the management of overweight and obesity, assuming that a single dietary strategy would be appropriate for all individuals. These studies have failed to provide strong evidence for the efficacy of any particular diet, and it is likely that different people will have different levels of success on different diets. We identified studies investigating pretreatment glycemia or insulinemia status, or both, of the individual as prognostic markers of weight loss during periods in which the composition of a participant's diet was known. Overall, research suggests that providing specific diets for weight management based on pretreatment glycemia and insulinemia statuses holds great promise for advancing personalized nutrition.

The Carbohydrate-Insulin Model of Obesity: Beyond "Calories In, Calories Out"

Despite intensive research, the causes of the obesity epidemic remain incompletely understood and conventional calorie-restricted diets continue to lack long-term efficacy. According to the carbohydrate-insulin model (CIM) of obesity, recent increases in the consumption of processed, high-glycemic-load carbohydrates produce hormonal changes that promote calorie deposition in adipose tissue, exacerbate hunger, and lower energy expenditure. Basic and genetic research provides mechanistic evidence in support of the CIM. In animals, dietary composition has been clearly demonstrated to affect metabolism and body composition, independently of calorie intake, consistent with CIM predictions. Meta-analyses of behavioral trials report greater weight loss with reduced-glycemic load vs low-fat diets, though these studies characteristically suffer from poor long-term compliance. Feeding studies have lacked the rigor and duration to test the CIM, but the longest such studies tend to show metabolic advantages for low-glycemic load vs low-fat diets. Beyond the type and amount of carbohydrate consumed, the CIM provides a conceptual framework for understanding how many dietary and nondietary exposures might alter hormones, metabolism, and adipocyte biology in ways that could predispose to obesity. Pending definitive studies, the principles of a low-glycemic load diet offer a practical alternative to the conventional focus on dietary fat and calorie restriction.

Protein engineering: Regulatory perspectives of stearoyl CoA desaturase

Stearoyl Co A desaturase (SCD) is a rate-limiting lipogenic enzyme that plays an integral role in catalyzing the synthesis of monounsaturated fatty acids, chiefly oleate and palmitoleate. Both contribute a major part of the biological membrane. Numerous SCD isoforms exist in mouse and humans, i.e., SCD-1 to SCD-4 and SCD-1 and SCD-5, respectively. From the biological viewpoint, hyperexpression of SCD1 cause many metabolic disorders including obesity, insulin resistance, hypertension, and hypertriglyceridemia, etc. Herein, an effort has been made to highlight the value of protein engineering in controlling the SCD-1 expression with the involvement of different inhibitors as therapeutic agents. The first part of the review describes Stearoyl CoA desaturase index and different SCD isoforms. Various regulatory aspects of SCD are reviewed in four subsections, i.e., (1) hormonal regulation, (2) regulation by dietary carbohydrates, (3) regulation by green tea, and (4) regulation via polyunsaturated fatty acids (PUFAs). Moreover, the regulation of Stearoyl CoA desaturase expression in the metabolism of fats and carbohydrates is discussed. The third part mainly focuses on natural and synthetic inhibitors. Towards the end, information is also given on potential future considerations of SCD-1 inhibitors as metabolic syndrome therapeutics, yet additional work is required.

Mild Suppression of Hyperinsulinemia to Treat Obesity and Insulin Resistance

Insulin plays roles in lipid uptake, lipolysis, and lipogenesis, in addition to controlling blood glucose levels. Excessive circulating insulin is associated with adipose tissue expansion and obesity, yet a causal role for hyperinsulinemia in the development of mammalian obesity has proven controversial, with many researchers suggesting it as a consequence of insulin resistance. Recently, evidence that specifically reducing hyperinsulinemia can prevent and reverse obesity in animal models has been presented. Our experiments, and others in this field, question the current dogma that hyperinsulinemia is a response to obesity and/or insulin resistance. In this review, we discuss preclinical evidence in the context of the broader literature and speculate on the possibility of clinical translation of alternative approaches for treating obesity.

Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults and the Association With Genotype Pattern or Insulin Secretion: The DIETFITS Randomized Clinical Trial

IMPORTANCE

Dietary modification remains key to successful weight loss. Yet, no one dietary strategy is consistently superior to others for the general population. Previous research suggests genotype or insulin-glucose dynamics may modify the effects of diets.

OBJECTIVE

To determine the effect of a healthy low-fat (HLF) diet vs a healthy low-carbohydrate (HLC) diet on weight change and if genotype pattern or insulin secretion are related to the dietary effects on weight loss.

DESIGN, SETTING, AND PARTICIPANTS

The Diet Intervention Examining The Factors Interacting with Treatment Success (DIETFITS) randomized clinical trial included 609 adults aged 18 to 50 years without diabetes with a body mass index between 28 and 40. The trial enrollment was from January 29, 2013, through April 14, 2015; the date of final follow-up was May 16, 2016. Participants were randomized to the 12-month HLF or HLC diet. The study also tested whether 3 single-nucleotide polymorphism multilocus genotype responsiveness patterns or insulin secretion (INS-30; blood concentration of insulin 30 minutes after a glucose challenge) were associated with weight loss.

INTERVENTIONS

Health educators delivered the behavior modification intervention to HLF (n = 305) and HLC (n = 304) participants via 22 diet-specific small group sessions administered over 12 months. The sessions focused on ways to achieve the lowest fat or carbohydrate intake that could be maintained long-term and emphasized diet quality.

MAIN OUTCOMES AND MEASURES

Primary outcome was 12-month weight change and determination of whether there were significant interactions among diet type and genotype pattern, diet and insulin secretion, and diet and weight loss.

RESULTS

Among 609 participants randomized (mean age, 40 [SD, 7] years; 57% women; mean body mass index, 33 [SD, 3]; 244 [40%] had a low-fat genotype; 180 [30%] had a low-carbohydrate genotype; mean baseline INS-30, 93 μIU/mL), 481 (79%) completed the trial. In the HLF vs HLC diets, respectively, the mean 12-month macronutrient distributions were 48% vs 30% for carbohydrates, 29% vs 45% for fat, and 21% vs 23% for protein. Weight change at 12 months was -5.3 kg for the HLF diet vs -6.0 kg for the HLC diet (mean between-group difference, 0.7 kg [95% CI, -0.2 to 1.6 kg]). There was no significant diet-genotype pattern interaction (P = .20) or diet-insulin secretion (INS-30) interaction (P = .47) with 12-month weight loss. There were 18 adverse events or serious adverse events that were evenly distributed across the 2 diet groups.

CONCLUSIONS AND RELEVANCE

In this 12-month weight loss diet study, there was no significant difference in weight change between a healthy low-fat diet vs a healthy low-carbohydrate diet, and neither genotype pattern nor baseline insulin secretion was associated with the dietary effects on weight loss. In the context of these 2 common weight loss diet approaches, neither of the 2 hypothesized predisposing factors was helpful in identifying which diet was better for whom.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01826591.

Relationship of insulin dynamics to body composition and resting energy expenditure following weight loss

OBJECTIVE

To examine associations of baseline insulin dynamics with changes in body composition and resting energy expenditure (REE) following weight loss.

METHODS

Twenty-one participants with overweight or obesity achieved 10-15% weight loss and then received 3 weight loss maintenance diets (high-carbohydrate, moderate-carbohydrate, and low-carbohydrate) in random order, each for 4 weeks. Body composition was measured at baseline and after weight loss. Insulin 30 min after glucose consumption (insulin-30; insulin response), C-peptide deconvolution analysis, HOMA, hepatic insulin sensitivity (IS), and REE were assessed at baseline and after each maintenance diet.

RESULTS

Insulin-30, but not maximal insulin secretion, hepatic IS, or HOMA, predicted changes in fat mass (standardized β = 0.385, 1.7 kg difference between 10th and 90th centile of insulin-30, P = 0.04) after weight loss. Insulin-30 (β = -0.341, -312 kcal day(-1) , P = 0.008), maximal insulin secretion (β = -0.216, -95 kcal day(-1) , P = 0.0002), HOMA (β = -0.394, -350 kcal day(-1) , P = 0.002), and hepatic IS (β = 0.217, 225 kcal day(-1) , P = 0.0003) predicted change in REE during weight loss maintenance, independent of changes in body composition. The inverse relationship between insulin-30 and REE was substantially attenuated when the low-carbohydrate diet was consumed first.

CONCLUSIONS

These findings distinguish a novel phenotype, characterized by high insulin response, at risk for weight regain, and identify a dietary approach to ameliorate this risk.

Providing food to treat adolescents at risk for cardiovascular disease

OBJECTIVE

Diet modification is recommended to treat childhood cardiovascular (CV) risk factors; however, the optimal dietary strategy is unknown.

METHODS

In a randomized trial, the effect of a low-fat (LF) and a low-glycemic-load (LGL) reduced-calorie diet were examined in youth with overweight/obesity with CV risk factors. Using a novel intervention, we delivered LF or LGL meals and nutrition education to the home for 8 weeks (Intensive Phase), followed by 4 months Maintenance without food provision. Between-group differences in the change in insulin area under the curve (InsAUC) by oral glucose tolerance test and other risk factors were analyzed.

RESULTS

Overall, participants (n = 27) showed substantial improvement during the Intensive Phase, including InsAUC (-59 ± 18.2 µU/ml × 120 min, P = 0.004), total cholesterol (-9.9 ± 3.6 mg/dl, P = 0.01), weight (-2.7 ± 0.5 kg, P < 0.001), waist circumference (-3.1 ± 0.8 cm, P < 0.001), HOMA-IR (-1.7 ± 0.4, P < 0.001), systolic blood pressure (-5 ± 1.4 mm Hg, P = 0.002), and CRP (-0.1 ± 0.1 mg/dl, P = 0.04). There were minimal between-group differences; the LF group showed greater declines in HDL (P = 0.005) and fasting glucose (P = 0.01) compared to the LGL group. Improvements waned during Maintenance.

CONCLUSIONS

Home delivery of LF or LGL diets resulted in rapid and clinically important improvements in CV risk factors that diminished without food delivery and did not differ based on dietary intervention. If scalable, food provision may represent an alternative nutrition treatment strategy.

Assessment of metabolic status in young Japanese females using postprandial glucose and insulin levels

Lifestyle-related diseases develop through the accumulation of undesirable lifestyle habits both prior to the onset of disease as well as during normal healthy life. Accordingly, early detection of, and intervention in, metabolic disorders is desirable, but is hampered by the lack of an established evaluation index for young individuals. The purpose of this study was to investigate the utility of a biomarker of health in young female subjects. The subjects were young healthy Japanese females in whom energy expenditure was measured for a period of 210 min after a test meal. In addition, Δplasma glucose and Δserum insulin were calculated from the fasting and 30 min values. ΔPlasma glucose and Δserum insulin levels varied widely compared to fasting levels. Both the area under the curve of carbohydrate oxidation rate and serum free fatty acid levels were higher in individuals in the high Δplasma glucose group. Moreover, Δplasma glucose was higher in individuals in the high Δserum insulin group than in the low Δserum insulin group. We conclude that nutritional balanced liquid loading test using Δplasma glucose and Δserum insulin as the evaluation index is useful for the detection of primary metabolic disorders in young females.

Findings from the Quebec Family Study on the Etiology of Obesity: Genetics and Environmental Highlights

The Quebec Family Study (QFS) was an observational study with three cycles of data collection between 1979 and 2002 in Quebec City, Canada. The cohort is a mixture of random sampling and ascertainment through obese individuals. The study has significantly contributed to our understanding of the determinants of obesity and associated disease risk over the past 35 years. In particular, the QFS cohort was used to investigate the contribution of familial resemblance and genetic effects on body fatness and behaviors related to energy balance. Significant familial aggregation and genetic heritability were reported for total adiposity, fat-free mass, subcutaneous fat distribution, abdominal and visceral fat, resting metabolic rate, physical activity level and other behavioral traits. The resources of QFS were also used to study the contribution of several nontraditional (non-caloric) risk factors as predictors of excess body weight and gains in weight and adiposity over time, including low calcium and micronutrient intake, high disinhibition eating behavior trait, and short sleep duration. An important finding relates to the interactions between dietary macronutrient intake and exercise intensity on body mass and adiposity.

Genetic epidemiology of cardiometabolic risk factors and their clustering patterns in Mexican American children and adolescents: the SAFARI Study

Pediatric metabolic syndrome (MS) and its cardiometabolic components (MSCs) have become increasingly prevalent, yet little is known about the genetics underlying MS risk in children. We examined the prevalence and genetics of MS-related traits among 670 non-diabetic Mexican American (MA) children and adolescents, aged 6-17 years (49 % female), who were participants in the San Antonio Family Assessment of Metabolic Risk Indicators in Youth study. These children are offspring or biological relatives of adult participants from three well-established Mexican American family studies in San Antonio, TX, at increased risk of type 2 diabetes. MS was defined as ≥3 abnormalities among 6 MSC measures: waist circumference, systolic and/or diastolic blood pressure, fasting insulin, triglycerides, HDL-cholesterol, and fasting and/or 2-h OGTT glucose. Genetic analyses of MS, number of MSCs (MSC-N), MS factors, and bivariate MS traits were performed. Overweight/obesity (53 %), pre-diabetes (13 %), acanthosis nigricans (33 %), and MS (19 %) were strikingly prevalent, as were MS components, including abdominal adiposity (32 %) and low HDL-cholesterol (32 %). Factor analysis of MS traits yielded three constructs: adipo-insulin-lipid, blood pressure, and glucose factors, and their factor scores were highly heritable. MS itself exhibited 68 % heritability. MSC-N showed strong positive genetic correlations with obesity, insulin resistance, inflammation, and acanthosis nigricans, and negative genetic correlation with physical fitness. MS trait pairs exhibited strong genetic and/or environmental correlations. These findings highlight the complex genetic architecture of MS/MSCs in MA children, and underscore the need for early screening and intervention to prevent chronic sequelae in this vulnerable pediatric population.

Effects of a low glycemic load or a low-fat dietary intervention on body weight in obese Hispanic American children and adolescents: a randomized controlled trial

BACKGROUND

In Hispanic children and adolescents, the prevalence of obesity and insulin resistance is considerably greater than in non-Hispanic white children. A low-glycemic load diet (LGD) has been proposed as an effective dietary intervention for pediatric obesity, but to our knowledge, no published study has examined the effects of an LGD in obese Hispanic children.

OBJECTIVE

We compared the effects of an LGD and a low-fat diet (LFD) on body composition and components of metabolic syndrome in obese Hispanic youth.

DESIGN

Obese Hispanic children (7-15 y of age) were randomly assigned to consume an LGD or an LFD in a 2-y intervention program. Body composition and laboratory assessments were obtained at baseline and 3, 12, and 24 mo after intervention.

RESULTS

In 113 children who were randomly assigned, 79% of both groups completed 3 mo of treatment; 58% of LGD and 55% of LFD subjects attended 24-mo follow-up. Compared with the LFD, the LGD decreased the glycemic load per kilocalories of reported food intakes in participants at 3 mo (P = 0.02). Both groups had a decreased BMI z score (P < 0.003), which was expressed as a standard z score relative to CDC age- and sex-specific norms, and improved waist circumference and systolic blood pressure (P < 0.05) at 3, 12, and 24 mo after intervention. However, there were no significant differences between groups for changes in BMI, insulin resistance, or components of metabolic syndrome (all P > 0.5).

CONCLUSIONS

We showed no evidence that an LGD and an LFD differ in efficacy for the reduction of BMI or aspects of metabolic syndrome in obese Hispanic youth. Both diets decreased the BMI z score when prescribed in the context of a culturally adapted, comprehensive weight-reduction program.

Insulin sensitivity affects propensity to obesity in an ethnic-specific manner: results from two controlled weight loss intervention studies

Background

Risk for obesity differs with ethnicity/race and is associated with insulin sensitivity (S_I), insulin responsiveness, and dietary glycemic load (GL). The objective of this study was to test the hypotheses that, 1) obesity-prone, normal weight, African-American (AA) women would be more insulin sensitive than BMI-matched, never overweight AA women; 2) increased adiposity over time would be associated with greater baseline S_I and higher dietary GL in AA but not European-American (EA) women; and 3) increased adiposity over time would be predicted by S_I in women with high but not low acute insulin response to glucose (AIRg).

Methods

Two controlled weight loss interventions were conducted involving overweight (BMI 25.0-29.9 kg/m²) premenopausal AA and EA women. The first included matching with normal-weight (BMI <25.0 kg/m²) controls following weight loss, and then comparing S_I. The second included a 1-year follow-up of weight-reduced participants to identify predictors of change in %body fat. Main outcome measure in the first study was insulin sensitivity (S_I) as assessed with intravenous glucose tolerance test (IVGTT), and in the second study was change in %fat, as assessed with DXA, over one year. AIRg was assessed during IVGTT, and free-living diet was determined by food record.

Results

In the first study, formerly overweight AA women were 43% more insulin sensitive than BMI-matched never overweight AA (P < 0.05). In the second study, S_I was positively associated with change in %fat over 1 year only in AA women (P < 0.05) and women with high AIRg (P < 0.05). In addition, AA who were insulin sensitive and who consumed a higher GL diet tended to gain greater %fat (P = 0.086 for diet x S_I interaction). In both studies, AA women had higher AIRg (P < 0.001) than EA women.

Conclusions

Formerly overweight (obesity-prone) AA women were more insulin sensitive than never overweight AA women, a quality that may predispose to adiposity, particularly when combined with a high GL diet. This ethnicity/race-specific effect may be due to high insulin responsiveness among AA.

Effects of dietary composition on energy expenditure during weight-loss maintenance

CONTEXT

Reduced energy expenditure following weight loss is thought to contribute to weight gain. However, the effect of dietary composition on energy expenditure during weight-loss maintenance has not been studied.

OBJECTIVE

To examine the effects of 3 diets differing widely in macronutrient composition and glycemic load on energy expenditure following weight loss.

DESIGN, SETTING, AND PARTICIPANTS

A controlled 3-way crossover design involving 21 overweight and obese young adults conducted at Children's Hospital Boston and Brigham and Women's Hospital, Boston, Massachusetts, between June 16, 2006, and June 21, 2010, with recruitment by newspaper advertisements and postings.

INTERVENTION

After achieving 10% to 15% weight loss while consuming a run-in diet, participants consumed an isocaloric low-fat diet (60% of energy from carbohydrate, 20% from fat, 20% from protein; high glycemic load), low-glycemic index diet (40% from carbohydrate, 40% from fat, and 20% from protein; moderate glycemic load), and very low-carbohydrate diet (10% from carbohydrate, 60% from fat, and 30% from protein; low glycemic load) in random order, each for 4 weeks.

MAIN OUTCOME MEASURES

Primary outcome was resting energy expenditure (REE), with secondary outcomes of total energy expenditure (TEE), hormone levels, and metabolic syndrome components.

RESULTS

Compared with the pre-weight-loss baseline, the decrease in REE was greatest with the low-fat diet (mean [95% CI], -205 [-265 to -144] kcal/d), intermediate with the low-glycemic index diet (-166 [-227 to -106] kcal/d), and least with the very low-carbohydrate diet (-138 [-198 to -77] kcal/d; overall P = .03; P for trend by glycemic load = .009). The decrease in TEE showed a similar pattern (mean [95% CI], -423 [-606 to -239] kcal/d; -297 [-479 to -115] kcal/d; and -97 [-281 to 86] kcal/d, respectively; overall P = .003; P for trend by glycemic load < .001). Hormone levels and metabolic syndrome components also varied during weight maintenance by diet (leptin, P < .001; 24-hour urinary cortisol, P = .005; indexes of peripheral [P = .02] and hepatic [P = .03] insulin sensitivity; high-density lipoprotein [HDL] cholesterol, P < .001; non-HDL cholesterol, P < .001; triglycerides, P < .001; plasminogen activator inhibitor 1, P for trend = .04; and C-reactive protein, P for trend = .05), but no consistent favorable pattern emerged.

CONCLUSION

Among overweight and obese young adults compared with pre-weight-loss energy expenditure, isocaloric feeding following 10% to 15% weight loss resulted in decreases in REE and TEE that were greatest with the low-fat diet, intermediate with the low-glycemic index diet, and least with the very low-carbohydrate diet.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00315354.

Reduced carbohydrate diet to improve metabolic outcomes and decrease adiposity in obese peripubertal African American girls

OBJECTIVE

Obesity prevalence among African American (AA) girls is higher than that in other groups. Because typical energy-restriction obesity treatment strategies have had limited success, alterations in macronutrient composition may effectively improve metabolic outcomes in this population and affect future body composition trajectories. The objective was to evaluate the efficacy of a moderately restricted carbohydrate (CHO) versus a standard CHO diet on weight/fat loss and metabolic parameters in overweight/obese AA girls ages 9 to 14 years.

METHODS

A total of 26 AA girls (ranging from 92nd body mass index percentile and above) were assigned to either a reduced- (SPEC: 42% energy from CHO, n = 12) or a standard- (STAN: 55% of energy from CHO, n = 14) CHO diet (protein held constant) for 16 weeks. All of the meals were provided and clinically tailored to meet the estimated energy requirements (resting energy expenditure × 1.2 in eucaloric phase and resting energy expenditure × 1.2 - 1000 kcal in energy deficit phase). The first 5 weeks encompassed a eucaloric phase evaluating metabolic changes in the absence of weight change. The subsequent 11 weeks were hypocaloric (1000 kcal/day deficit) to promote weight/fat loss. Meal tests were performed during the eucaloric phase for metabolic analyses. Dual-energy x-ray absorptiometry was used to evaluate body composition.

RESULTS

Both groups experienced reductions in weight/adiposity, but the difference did not reach significance. The solid meal test indicated improved glucose/insulin homeostasis on the SPEC diet up to 3 hours postingestion. In addition, significantly lower triglycerides (P < 0.001) were observed on the SPEC diet.

CONCLUSIONS

Dietary CHO reduction favorably influences metabolic parameters but did not result in greater weight/fat loss relative to a standard diet in obese AA girls. Future research is needed to determine long-term effectiveness of a reduced CHO diet on glucose and insulin homeostasis and how it may apply to weight maintenance/fat loss during development alone and/or in combination with additional weight loss/metabolic improvement strategies.

A distinct adipose tissue gene expression response to caloric restriction predicts 6-mo weight maintenance in obese subjects

BACKGROUND

Weight loss has been shown to reduce risk factors associated with cardiovascular disease and diabetes; however, successful maintenance of weight loss continues to pose a challenge.

OBJECTIVE

The present study was designed to assess whether changes in subcutaneous adipose tissue (scAT) gene expression during a low-calorie diet (LCD) could be used to differentiate and predict subjects who experience successful short-term weight maintenance from subjects who experience weight regain.

DESIGN

Forty white women followed a dietary protocol consisting of an 8-wk LCD phase followed by a 6-mo weight-maintenance phase. Participants were classified as weight maintainers (WMs; 0-10% weight regain) and weight regainers (WRs; 50-100% weight regain) by considering changes in body weight during the 2 phases. Anthropometric measurements, bioclinical variables, and scAT gene expression were studied in all individuals before and after the LCD. Energy intake was estimated by using 3-d dietary records.

RESULTS

No differences in body weight and fasting insulin were observed between WMs and WRs at baseline or after the LCD period. The LCD resulted in significant decreases in body weight and in several plasma variables in both groups. WMs experienced a significant reduction in insulin secretion in response to an oral-glucose-tolerance test after the LCD; in contrast, no changes in insulin secretion were observed in WRs after the LCD. An ANOVA of scAT gene expression showed that genes regulating fatty acid metabolism, citric acid cycle, oxidative phosphorylation, and apoptosis were regulated differently by the LCD in WM and WR subjects.

CONCLUSION

This study suggests that LCD-induced changes in insulin secretion and scAT gene expression may have the potential to predict successful short-term weight maintenance. This trial was registered at clinicaltrials.gov as NCT00390637.

d-Fagomine lowers postprandial blood glucose and modulates bacterial adhesion

d-Fagomine is an iminosugar originally isolated from seeds of buckwheat (Fagopyrum sculentumMoench), present in the human diet and now available as a pure crystalline product. We testedd-fagomine for activities connected to a reduction in the risk of developing insulin resistance, becoming overweight and suffering from an excess of potentially pathogenic bacteria. The activities were: intestinal sucrase inhibitionin vitro(rat mucosa and everted intestine sleeves), modulation of postprandial blood glucose in rats, bacterial agglutination and bacterial adhesion to pig intestinal mucosa. When ingested together with sucrose or starch,d-fagomine lowered blood glucose in a dose-dependent manner without stimulating insulin secretion.d-Fagomine reduced the area under the curve (0–120 min) by 20 % (P < 0·01) and shifted the time to maximum blood glucose concentration (Tmax) by 15 min at doses of 1–2 mg/kg body weight when administered together with 1 g sucrose/kg body weight. Moreover,d-fagomine (0·14 mm) agglutinated 60 % of Enterobacteriaceae (Escherichia coli,Salmonella entericaserovar Typhimurium) populations (P < 0·01), while it did not show this effect onBifidobacteriumspp. orLactobacillusspp. At the same concentration,d-fagomine significantly (P < 0·001) inhibited the adhesion of Enterobacteriaceae (95–99 % cells in the supernatant) and promoted the adhesion ofLactobacillus acidophilus(56 % cells in the supernatant) to intestinal mucosa.d-Fagomine did not show any effect on bacterial cell viability. Based on all this evidence,d-fagomine may be used as a dietary ingredient or functional food component to reduce the health risks associated with an excessive intake of fast-digestible carbohydrates, or an excess of potentially pathogenic bacteria.

Role of low-glycemic index diet in management of childhood obesity

Conventional dietary recommendation for obesity management is a low-fat energy-restricted diet, which however, only have modest and non-sustained effects on weight reduction. Alternative dietary interventions, including low-glycemic index (GI) diet, have been proposed. Glycemic index is a measure of blood glucose excursion per unit of carbohydrate. Foods with high GI are rapidly digested, absorbed and transformed into glucose. These processes cause accelerated and transient surges in blood glucose and insulin, earlier return of hunger sensation and excessive caloric intake. Conversely, low-GI diet decreases blood glucose and insulin excursion, promotes greater fat oxidation, decreases lipogenesis and increases satiety. Modern food-processing technology has produced many food products with high GI which may contribute to the burgeoning epidemic of obesity especially in children/adolescents. Epidemiological and clinical trials suggest a role for low-GI diet in the management of childhood obesity and associated cardio-metabolic risks although results are not always consistent. In this article, we shall review the physiological basis and current evidence for and against low-GI diet in obesity management, with particular focus in children and adolescents.

Dietary macronutrient composition affects β cell responsiveness but not insulin sensitivity

BACKGROUND

Altering dietary carbohydrate or fat content may have chronic effects on insulin secretion and sensitivity, which may vary with individual metabolic phenotype.

OBJECTIVE

The objective was to evaluate the contribution of tightly controlled diets differing in carbohydrate and fat content for 8 wk to insulin sensitivity and β cell responsiveness and whether effects of diet would vary with race, free-living diet, or insulin response.

DESIGN

Healthy overweight men and women (36 European Americans, 33 African Americans) were provided with food for 8 wk and received either a eucaloric standard diet (55% carbohydrate, 27% fat) or a eucaloric reduced-carbohydrate (RedCHO)/higher-fat diet (43% carbohydrate, 39% fat). Insulin sensitivity and β cell responsiveness were assessed at baseline and 8 wk by using a liquid meal tolerance test.

RESULTS

Insulin sensitivity did not change with diet (P = 0.1601). Static β cell response to glucose (ФS) was 28.5% lower after the RedCHO/higher-fat diet. Subgroup analyses indicated that lower ФS with the RedCHO/higher-fat diet occurred primarily among African Americans. A significant inverse association was observed for change in glucose area under the curve compared with change in ФS.

CONCLUSIONS

Consumption of a eucaloric 43% carbohydrate/39% fat diet for 8 wk resulted in down-regulation of β cell responsiveness, which was influenced by baseline phenotypic characteristics. Further study is needed to probe the potential cause-and-effect relation between change in ФS and change in glucose tolerance. This trial is registered at clinicaltrials.gov as NCT00726908.

Effects of high and low glycemic load meals on energy intake, satiety and hunger in obese Hispanic-American youth

Some short-term pediatric studies have suggested beneficial effects of low glycemic load (LGL) meals on feelings of hunger and on energy intake. However, the effects of LGL diets have not been systematically studied in obese Hispanic children, who stand to benefit from successful interventions.

OBJECTIVE

To examine the effects of LGL and high-GL (HGL) meals on appetitive responses and ad libitum energy intake of obese Hispanic youth.

METHODS

A total of 88 obese Hispanic youth aged 7-15 years were enrolled in a community-based obesity intervention program and randomly assigned to consume meals designed as either LGL (n = 45) or HGL (n = 43). After 12 weeks, participants were admitted for a 24-hour metabolic study. Following the morning test meal, subjects serially reported hunger, fullness, and satiety using a visual analog scale. Blood insulin and glucose were measured. After 5 hours, participants were fed another test meal and given a snack platter from which to eat ad libitum. All test food was weighed and the energy, macronutrients, and glycemic load (GL) of consumed foods were calculated.

RESULTS

The HGL group had significantly higher insulin (p = 0.0005) and glucose (p = 0.0001) responses to the breakfast meal compared with the LGL group. There were no significant between-group differences in energy consumed from the snack platter (1303 vs. 1368 kcal, p = 0.5), or in the subjective feelings of hunger (p = 0.3), fullness (p = 0.5) or satiety (p = 0.3) between the two groups.

CONCLUSIONS

Our study provides no evidence that, for obese Hispanic youth, changing the GL of the diet affects short-term hunger, fullness, satiety, or energy intake. ClinicalTrials.gov Identifier: NCT01068197.

Glucose metabolism and diet predict changes in adiposity and fat distribution in weight-reduced women

Among obesity-prone individuals, metabolic state may interact with diet in determining body composition. We tested the hypotheses that, among 103 weight-reduced women over 1 year, (i) insulin sensitivity would be positively associated with change in %fat; (ii) this association would be modulated by dietary glycemic load (GL); and (iii) changes in fat distribution would be related to indexes of glucose metabolism. Insulin sensitivity, glucose effectiveness, fasting and postchallenge insulin and glucose, and glucose tolerance were assessed during intravenous glucose tolerance test (IVGTT). Changes in %fat and fat distribution were examined using dual-energy X-ray absorptiometry and computed tomography. Dietary GL was assessed on 67 women using food records. On average, women showed a +5.3 +/- 3.0% change in %fat over 1 year, with the magnitude of this change being greater in relatively insulin sensitive women (+6.0 +/- 0.4%, mean +/- s.e.m.) than in relatively insulin resistant women (+4.4 +/- 0.4 kg; P < 0.05). Women who were relatively insulin sensitive and who consumed a higher GL diet showed a +6.8 +/- 0.7% change in %fat, which was greater than those who were less insulin sensitive, regardless of diet (P < 0.05), but did not differ from women who were relatively insulin sensitive and who consumed a lower GL diet (P = 0.105). Changes in intra-abdominal and deep subcutaneous abdominal fat were inversely associated with the postchallenge decline in serum glucose. In conclusion, greater insulin sensitivity may predispose to adiposity among weight reduced women, an effect that may be ameliorated by a lower GL diet. The potential association between indexes of glucose disposal and changes in fat distribution warrants further study.

Long-term nutrition education reduces several risk factors for type 2 diabetes mellitus in Brazilians with impaired glucose tolerance

The aim of this study was to evaluate the effects of a nutrition education program (NEP) on anthropometric, dietetic, and metabolic parameters in high-risk subjects for type 2 diabetes mellitus. Fifty-one participants, both sexes, were randomly assigned to either the control (58.8%) or the intervention (NEP) group. The intervention group received frequent individual and group nutritional counseling from a team of nutritionists. Participants were assessed at baseline (M0) and after 12 months (M1) for anthropometric, dietetic, and metabolic parameters. The hypothesis was that high-risk subjects for type 2 diabetes mellitus participating in NEP would show an improvement in these parameters. At M1, the intervention group showed a significant decline in body weight (-3.4%), body mass index (-5.7%), cholesterol intake (-49.5%), fasting glycemia (-14.0%), fasting insulin (-9.0%), postprandial glycemia (-21.0%), postprandial insulin (-71.0%), total serum cholesterol (-23.0%), and glycated hemoglobin (-24.0%). A decrease in energy intake (5%, P = .06) and low-density lipoprotein cholesterol (25%, P = .07) was observed in the interventional group, although it did not reach statistical significance. In contrast, the control group presented a significantly higher energy intake (19%, P = .04) and a nonsignificant increase in consumption of all macronutrients. The long-term NEP was found to improve anthropometric, dietary, and metabolic parameters in high-risk subjects for type 2 diabetes mellitus.

The glycemic index: physiological significance

The glycemic index (GI) is a physiological assessment of a food's carbohydrate content through its effect on postprandial blood glucose concentrations. Evidence from trials and observational studies suggests that this physiological classification may have relevance to those chronic Western diseases associated with overconsumption and inactivity leading to central obesity and insulin resistance. The glycemic index classification of foods has been used as a tool to assess potential prevention and treatment strategies for diseases where glycemic control is of importance, such as diabetes. Low GI diets have also been reported to improve the serum lipid profile, reduce C-reactive protein (CRP) concentrations, and aid in weight control. In cross-sectional studies, low GI or glycemic load diets (mean GI multiplied by total carbohydrate) have been associated with higher levels of high-density lipoprotein cholesterol (HDL-C), with reduced CRP concentrations, and, in cohort studies, with decreased risk of developing diabetes and cardiovascular disease. In addition, some case-control and cohort studies have found positive associations between dietary GI and risk of various cancers, including those of the colon, breast, and prostate. Although inconsistencies in the current findings still need to be resolved, sufficient positive evidence, especially with respect to renewed interest in postprandial events, suggests that the glycemic index may have a role to play in the treatment and prevention of chronic diseases.

Stearoyl-CoA desaturase and its relation to high-carbohydrate diets and obesity

Obesity is currently a worldwide epidemic and public health burden that increases the risk for developing insulin resistance and several chronic diseases such as diabetes, cardiovascular diseases and non-alcoholic fatty liver disease. The multifactorial causes of obesity include several genetic, dietary and lifestyle variables that together result in an imbalance between energy intake and energy expenditure. Dietary approaches to limit fat intake are commonly prescribed to achieve the hypocaloric conditions necessary for weight loss. But dietary fat restriction is often accompanied by increased carbohydrate intake, which can dramatically increase endogenous fatty acid synthesis depending upon carbohydrate composition. Since both dietary and endogenously synthesized fatty acids contribute to the whole-body fatty acid pool, obesity can therefore result from excessive fat or carbohydrate consumption. Stearoyl-Coenzyme A desaturase-1 (SCD1) is a delta-9 fatty acid desaturase that converts saturated fatty acids into monounsaturated fatty acids (MUFA) and this activity is elevated by dietary carbohydrate. Mice lacking Scd1 are protected from obesity and insulin resistance and are characterized by decreased fatty acid synthesis and increased fatty acid oxidation. In this review, we address the association of high-carbohydrate diets with increased SCD activity and summarize the current literature on the subject of SCD1 and body weight regulation.