Randomized, multi-center trial of two hypo-energetic diets in obese subjects: high- versus low-fat content

Beneficial effects of a Paleolithic diet on cardiovascular risk factors in type 2 diabetes: a randomized cross-over pilot study

BACKGROUND

Our aim was to compare the effects of a Paleolithic ('Old Stone Age') diet and a diabetes diet as generally recommended on risk factors for cardiovascular disease in patients with type 2 diabetes not treated with insulin.

METHODS

In a randomized cross-over study, 13 patients with type 2 diabetes, 3 women and 10 men, were instructed to eat a Paleolithic diet based on lean meat, fish, fruits, vegetables, root vegetables, eggs and nuts; and a Diabetes diet designed in accordance with dietary guidelines during two consecutive 3-month periods. Outcome variables included changes in weight, waist circumference, serum lipids, C-reactive protein, blood pressure, glycated haemoglobin (HbA1c), and areas under the curve for plasma glucose and plasma insulin in the 75 g oral glucose tolerance test. Dietary intake was evaluated by use of 4-day weighed food records.

RESULTS

Study participants had on average a diabetes duration of 9 years, a mean HbA1c of 6,6% units by Mono-S standard and were usually treated with metformin alone (3 subjects) or metformin in combination with a sulfonylurea (3 subjects) or a thiazolidinedione (3 subjects). Mean average dose of metformin was 1031 mg per day. Compared to the diabetes diet, the Paleolithic diet resulted in lower mean values of HbA1c (-0.4% units, p = 0.01), triacylglycerol (-0.4 mmol/L, p = 0.003), diastolic blood pressure (-4 mmHg, p = 0.03), weight (-3 kg, p = 0.01), BMI (-1 kg/m2, p = 0.04) and waist circumference (-4 cm, p = 0.02), and higher mean values of high density lipoprotein cholesterol (+0.08 mmol/L, p = 0.03). The Paleolithic diet was mainly lower in cereals and dairy products, and higher in fruits, vegetables, meat and eggs, as compared with the Diabetes diet. Further, the Paleolithic diet was lower in total energy, energy density, carbohydrate, dietary glycemic load, saturated fatty acids and calcium, and higher in unsaturated fatty acids, dietary cholesterol and several vitamins. Dietary GI was slightly lower in the Paleolithic diet (GI = 50) than in the Diabetic diet (GI = 55).

CONCLUSION

Over a 3-month study period, a Paleolithic diet improved glycemic control and several cardiovascular risk factors compared to a Diabetes diet in patients with type 2 diabetes.

Several obesity- and nutrient-related gene polymorphisms but not FTO and UCP variants modulate postabsorptive resting energy expenditure and fat-induced thermogenesis in obese individuals: the NUGENOB study

BACKGROUND

Part of the heterogeneity of the obesity phenotype may originate from genetic differences between obese individuals that may influence energy expenditure (EE).

OBJECTIVE

To examine if common single-nucleotide polymorphisms (SNPs) in genes related to obesity-associated phenotypes are associated with postabsorptive resting energy expenditure (REE) and postprandial REE in obese individuals.

DESIGN AND METHODS

Postabsorptive REE and 3-h postprandial REE (liquid test meal containing 95% fat, energy content 50% of estimated REE) were measured in 743 obese individuals from eight clinical centres in seven European countries. The analysis assessed the association of genotypes of 44 SNPs in 28 obesity-related candidate genes with postabsorptive REE and postprandial REE taking into consideration the influence of body composition, habitual physical activity, insulin sensitivity, circulating thermogenic hormones and metabolites.

RESULTS

After adjustment for fat-free mass (FFM), age, sex and research centre, SNPs in CART, GAD2, PCSK1, PPARG3, HSD11B1 and LIPC were significantly associated with postabsorptive REE. SNPs in GAD2, HSD11B1 and LIPC remained significantly associated with postabsorptive REE after further adjustment for fat mass (FM). SNPs in CART, PPARG2 and IGF2 were significantly associated with postprandial REE after similar adjustments. These associations with postprandial REE remained significant after further adjustment for FM. FTO, UCP2 and UCP3 variants were not associated with postabsorptive or postprandial REE.

CONCLUSIONS

Several gene polymorphisms associated with obesity-related phenotypes but not FTO and UCP variants may be responsible for some of the inter-individual variability in postabsorptive REE and fat-induced thermogenesis unaccounted for by FFM, FM, age and sex. The association between FTO and obesity that has been reported earlier may not be mediated directly through modulation of EE in obese individuals.

Fasting and postprandial remnant-like particle cholesterol concentrations in obese participants are associated with plasma triglycerides, insulin resistance, and body fat distribution

Elevated plasma concentrations of remnant-like particle cholesterol (RLP-C) are atherogenic. However, factors that determine RLP-C are not fully understood. This study evaluates which factors affect RLP-C in the fasting and postprandial state, using multiple regression analyses in a large cohort of lean and obese participants. All participants (n = 740) underwent a test meal challenge containing 95 energy % (en%) fat (energy content 50% of predicted daily resting metabolic rate). Fasting and postprandial concentrations of circulating metabolites were measured over a 3-h period. Obese participants (n = 613) also participated in a 10-wk weight loss program (-2510 kJ/d), being randomized to either a low-fat or a high-fat diet (20-25 vs. 40-45en% fat). Postprandial RLP-C was associated with fasting RLP-C, waist:hip ratio (WHR), HOMA(IR) (homeostasis model assessment index for insulin resistance) (P < 0.001), and age, independently of BMI and gender [adjusted R(2) (adj. R(2)) = 0.70). These factors were also related to fasting RLP-C (P < 0.010), along with gender and physical activity (adj. R(2) = 0.23). The dietary intervention resulted in significantly lower fasting RLP-C concentrations, independently mediated by weight loss, improvements in HOMA(IR), and the fat content of the prescribed diet. However, after inclusion of plasma triglyceride (TG), HDL-cholesterol, and FFA concentrations in the models, HOMA(IR) and WHR no longer significantly predicted fasting RLP-C, although WHR remained a predictor of postprandial RLP-C (P = 0.002). Plasma TG was strongly associated with both fasting and postprandial RLP-C (P < 0.001). In conclusion, plasma RLP-C concentrations are mainly associated with plasma TG concentrations. Interestingly, the high-fat diet was more effective at decreasing fasting RLP-C concentrations in obese participants than the low-fat diet.

Comparison of 3 ad libitum diets for weight-loss maintenance, risk of cardiovascular disease, and diabetes: a 6-mo randomized, controlled trial

BACKGROUND

The optimal dietary content and type of fat and carbohydrate for weight management has been debated for decades.

OBJECTIVE

The objective was to compare the effects of 3 ad libitum diets on the maintenance of an initial weight loss of >or=8% and risk factors for CVD and diabetes during a 6-mo controlled dietary intervention.

DESIGN

Nondiabetic overweight or obese [mean +/- SD body mass index (in kg/m(2)): 31.5 +/- 2.6] men (n = 55) and women (n = 76) aged 28.2 +/- 4.8 y were randomly assigned to a diet providing a moderate amount of fat (35-45% of energy) and >20% of fat as monounsaturated fatty acids (MUFA diet; n = 54), to a low-fat (20-30% of energy) diet (LF diet; n = 51), or to a control diet (35% of energy as fat; n = 26). Protein constituted 10-20% of energy in all 3 diets. All foods were provided free of charge from a purpose-built supermarket.

RESULTS

More subjects dropped out of the MUFA (28%) group than out of the LF group (16%) and control group (8%) (MUFA compared with control: P < 0.05). All groups regained weight (MUFA: 2.5 +/- 0.7 kg; LF: 2.2 +/- 0.7 kg; and control: 3.8 +/- 0.8 kg; NS). Body fat regain was lower in the LF (0.6 +/- 0.6%) and MUFA (1.6 +/- 0.6%) groups than in the control group (2.6 +/- 0.5%) (P < 0.05). In the MUFA group, fasting insulin decreased by 2.6 +/- 3.5 pmol/L, the homeostasis model assessment of insulin resistance by 0.17 +/- 0.13, and the ratio of LDL to HDL by 0.33 +/- 0.13; in the LF group, these variables increased by 4.3 +/- 3.0 pmol/L (P < 0.08) and 0.17 +/- 0.10 (P < 0.05) and decreased by 0.02 +/- 0.09 (P = 0.005), respectively; and in the control group, increased by 14.0 +/- 4.3 pmol/L (P < 0.001), 0.57 +/- 0.17 (P < 0.001), and 0.05 +/- 0.14 (P = 0.036), respectively. Dietary adherence was high on the basis of fatty acid changes in adipose tissue.

CONCLUSIONS

Diet composition had no major effect on preventing weight regain. However, both the LF and MUFA diets produced less body fat regain than did the control diet, and the dropout rate was lowest in the LF diet group, whereas fasting insulin decreased and the homeostasis model assessment of insulin resistance and ratio of LDL to HDL improved with the MUFA diet. This trial was registered at clinicaltrials.gov as NCT00274729.

Total adiponectin and adiponectin multimeric complexes in relation to weight loss-induced improvements in insulin sensitivity in obese women: the NUGENOB study

AIM

Adiponectin increases insulin sensitivity, protects arterial walls against atherosclerosis, and regulates glucose metabolism, and is decreased in obese, insulin resistant, and type 2 diabetic patients. Adiponectin circulates in plasma as high, medium, and low molecular weight forms (HMW, MMW, and LMW). The HMW form was suggested to be closely associated with insulin sensitivity. This study investigated whether diet-induced changes in insulin sensitivity were associated with changes in adiponectin multimeric complexes.

SUBJECTS

Twenty obese women with highest and twenty obese women with lowest diet induced changes in insulin sensitivity (responders and non-responders respectively), matched for weight loss (body mass index (BMI)=34.5 (s.d. 2.9) resp. 36.5 kg/m(2) (s.d. 4.0) for responders and non-responders), were selected from 292 women who underwent a 10-week low-caloric diet (LCD; 600 kcal/d less than energy requirements). Plasma HMW, MMW, and LMW forms of adiponectin were quantified using Western blot method.

RESULTS

LCD induced comparable weight reduction in responders and non-responders by 8.2 and 7.6 kg. Homeostasis model assessment insulin resistance index decreased by 48.1% in responders and remained unchanged in non-responders. Total plasma adiponectin and the quantity of HMW and MMW remained unchanged in both groups, while LMW increased by 16.3% in non-responders. No differences between both groups were observed at baseline and after the study. Total plasma adiponectin, MMW, and LMW were negatively associated with fasting insulin levels at baseline.

CONCLUSION

No differences in total plasma adiponectin, HMW, MMW, and LMW forms were observed between responders and non-responders following 10-week LCD, suggesting that adiponectin is not a major determinant of weight loss-induced improvements in insulin sensitivity.

Effects of TCF7L2 polymorphisms on obesity in European populations

The transcription factor 7-like 2 (TCF7L2) rs7903146 T allele was previously associated with type 2 diabetes (T2D) and decreased BMI whereas haplotypes carrying the rs7903146 C and rs10885406 A alleles (HapA) were associated with increased BMI. The functional relevance of TCF7L2 polymorphisms and their effects on T2D and obesity remained to be further investigated. In white European populations, we found that the rs7903146 T allele was more associated with T2D in 3,547 non-obese individuals (odds ratio (OR) = 1.88 (1.69-2.10)) than in 1,110 class III obese subjects (OR = 1.24 (1.03-1.50)). No direct effect of the rs7903146 C allele and HapA was found on any form of obesity in 3,507 normal glucose tolerant (NGT) individuals, 1,106 pedigrees with familial obesity and 5,512 individuals from the French general population. However, in T2D subjects, the rs7903146 C allele was less prevalent in the 1,111 non-obese individuals (55.2%) compared to 659 class III obese subjects (67.5% OR = 1.69 (1.46-1.95)). Functional studies showed that the rs7903146 T allele is less prone to be bound by protein factors than the C allele in 3T3-L1, HepG2 and beta-TC3 cell lines and that TCF7L2 expression decreases in subcutaneous adipose tissue from NGT obese T/T carriers under calorie restriction. In conclusion, TCF7L2 is not a risk factor for obesity in European populations, but its effect on T2D risk is modulated by obesity. Furthermore, our data suggest that the rs7903146 T allele may be possibly functional and associated with a nominal decrease in TCF7L2 expression in adipose tissue of individuals under calorie restriction.

Adipose gene expression prior to weight loss can differentiate and weakly predict dietary responders

BACKGROUND

The ability to identify obese individuals who will successfully lose weight in response to dietary intervention will revolutionize disease management. Therefore, we asked whether it is possible to identify subjects who will lose weight during dietary intervention using only a single gene expression snapshot.

METHODOLOGY/PRINCIPAL FINDINGS

The present study involved 54 female subjects from the Nutrient-Gene Interactions in Human Obesity-Implications for Dietary Guidelines (NUGENOB) trial to determine whether subcutaneous adipose tissue gene expression could be used to predict weight loss prior to the 10-week consumption of a low-fat hypocaloric diet. Using several statistical tests revealed that the gene expression profiles of responders (8-12 kgs weight loss) could always be differentiated from non-responders (<4 kgs weight loss). We also assessed whether this differentiation was sufficient for prediction. Using a bottom-up (i.e. black-box) approach, standard class prediction algorithms were able to predict dietary responders with up to 61.1%+/-8.1% accuracy. Using a top-down approach (i.e. using differentially expressed genes to build a classifier) improved prediction accuracy to 80.9%+/-2.2%.

CONCLUSION

Adipose gene expression profiling prior to the consumption of a low-fat diet is able to differentiate responders from non-responders as well as serve as a weak predictor of subjects destined to lose weight. While the degree of prediction accuracy currently achieved with a gene expression snapshot is perhaps insufficient for clinical use, this work reveals that the comprehensive molecular signature of adipose tissue paves the way for the future of personalized nutrition.

Plasma levels and adipose tissue messenger ribonucleic acid expression of retinol-binding protein 4 are reduced during calorie restriction in obese subjects but are not related to diet-induced changes in insulin sensitivity

CONTEXT

Retinol-binding protein 4 (RBP4) may play a role in the development of insulin resistance.

OBJECTIVE

We investigated whether RBP4 adipose tissue mRNA expression and plasma level are related to insulin sensitivity during a diet-induced weight loss.

DESIGN, SETTING, PATIENTS, AND INTERVENTION

Obese women followed a dietary intervention composed of a 4-wk very low-calorie diet (VLCD), a 2-month low-calorie diet, and 3-4 months of a weight maintenance (WM) phase.

MAIN OUTCOME MEASURES

Clinical investigation was performed before and at the end of each phase. Insulin sensitivity was assessed with the euglycemic hyperinsulinemic clamp. Adipose tissue mRNA and plasma levels of RBP4 were determined using reverse transcription-quantitative PCR and ELISA, respectively.

RESULTS

Weight and fat mass decreased during VLCD and were stabilized during WM. Glucose disposal rate increased during VLCD and remained elevated thereafter. Plasma levels of RBP4 decreased after VLCD and, although increasing at subsequent phases, remained lower than prediet values. Adipose tissue mRNA levels were diminished after VLCD, and increased during low-calorie diet and WM to reach basal values. Basal RBP4 levels or diet-induced variations of RBP4 were not different in lean women and two groups of obese women with high- and low-insulin sensitivity.

CONCLUSIONS

Severe calorie restriction promotes a reduction in adipose tissue and plasma levels of RBP4. The study does not bring evidence for a role for RBP4 in the regulation of diet-induced changes in insulin sensitivity.

Adipose triglyceride lipase and hormone-sensitive lipase protein expression is decreased in the obese insulin-resistant state

AIM/HYPOTHESIS

Obesity is associated with increased triacylglycerol (TAG) storage in adipose tissue and insulin resistance. The mobilization of stored TAG is mediated by hormone-sensitive lipase (HSL) and the recently discovered adipose triglyceride lipase (ATGL). The aim of the present study was to examine whether ATGL and HSL mRNA and protein expression are altered in insulin-resistant conditions. In addition, we investigated whether a possible impaired expression could be reversed by a period of weight reduction.

METHODS

Adipose tissue biopsies were taken from obese subjects (n = 44) with a wide range of insulin resistance, before and just after a 10-wk hypocaloric diet. ATGL and HSL protein and mRNA expression was determined by Western blot and quantitative RT-PCR, respectively.

RESULTS

Fasting insulin levels and the degree of insulin resistance (using the homeostasis model assessment index for insulin resistance) were negatively correlated with ATGL and HSL protein expression, independent of age, gender, fat cell size, and body composition. Both mRNA and protein levels of ATGL and HSL were reduced in insulin-resistant compared with insulin-sensitive subjects (P < 0.05). Weight reduction significantly decreased ATGL and HSL mRNA and protein expression. A positive correlation between the decrease in leptin and the decrease in ATGL protein level after weight reduction was observed. Finally, ATGL and HSL mRNA and protein levels seem to be highly correlated, indicating a tight coregulation and transcriptional control.

CONCLUSIONS

In obese subjects, insulin resistance and hyperinsulinemia are strongly associated with ATGL and HSL mRNA and protein expression, independent of fat mass. Data on weight reduction indicated that also other factors (e.g. leptin) relate to ATGL and HSL protein expression.

Genetic polymorphisms and weight loss in obesity: a randomised trial of hypo-energetic high- versus low-fat diets

Objectives:

To study if genes with common single nucleotide polymorphisms (SNPs) associated with obesity-related phenotypes influence weight loss (WL) in obese individuals treated by a hypo-energetic low-fat or high-fat diet.

Design:

Randomised, parallel, two-arm, open-label multi-centre trial.

Setting:

Eight clinical centres in seven European countries.

Participants:

771 obese adult individuals.

Interventions:

10-wk dietary intervention to hypo-energetic (−600 kcal/d) diets with a targeted fat energy of 20%–25% or 40%–45%, completed in 648 participants.

Outcome Measures:

WL during the 10 wk in relation to genotypes of 42 SNPs in 26 candidate genes, probably associated with hypothalamic regulation of appetite, efficiency of energy expenditure, regulation of adipocyte differentiation and function, lipid and glucose metabolism, or production of adipocytokines, determined in 642 participants.

Results:

Compared with the noncarriers of each of the SNPs, and after adjusting for gender, age, baseline weight and centre, heterozygotes showed WL differences that ranged from −0.6 to 0.8 kg, and homozygotes, from −0.7 to 3.1 kg. Genotype-dependent additional WL on low-fat diet ranged from 1.9 to −1.6 kg in heterozygotes, and from 3.8 kg to −2.1 kg in homozygotes relative to the noncarriers. Considering the multiple testing conducted, none of the associations was statistically significant.

Conclusions:

Polymorphisms in a panel of obesity-related candidate genes play a minor role, if any, in modulating weight changes induced by a moderate hypo-energetic low-fat or high-fat diet.

Background: Obesity is an important cause of death and disease, particularly in the developed world. It is understood that both environmental and genetic factors contribute towards obesity. Numerous studies have associated particular gene variants with a tendency towards obesity, but it is not known whether such gene variants affect the degree to which obese individuals will lose weight when dieting.

What this trial shows: As part of a randomised trial, 771 participants were assigned to one of two different low-energy diets for 10 weeks: one low in fat or one high in fat. The researchers then did a genetic analysis of 642 participants completing the intervention, to find out whether any of 42 distinct genetic variations in 26 genes were associated with weight loss in the trial. The genetic variants were chosen for study as they were known or already thought to be associated with appetite regulation or various aspects of metabolism and fat tissue development and function. The investigators found that none of the genetic variants studied had a significant association with weight loss in the trial. It was also seen that the majority of genetic variants were not associated with efficacy of one dietary intervention over another.

Strengths and limitations: Although a large number of participants was recruited into the trial, the genetic analysis involved multiple comparisons—168 tests of 42 genetic variants. This increases the likelihood that any significant associations found could have resulted from chance alone. Significant associations from this study will require additional confirmation in larger studies.

Contribution to the evidence: This study adds data indicating that variation in the genes studied did not have an important influence on weight loss.

Assessing the performance of statistical validation tools for megavariate metabolomics data

Statistical model validation tools such as cross-validation, jack-knifing model parameters and permutation tests are meant to obtain an objective assessment of the performance and stability of a statistical model. However, little is known about the performance of these tools for megavariate data sets, having, for instance, a number of variables larger than 10 times the number of subjects. The performance is assessed for megavariate metabolomics data, but the conclusions also carry over to proteomics, transcriptomics and many other research areas. Partial least squares discriminant analyses models were built for several LC-MS lipidomic training data sets of various numbers of lean and obese subjects. The training data sets were compared on their modelling performance and their predictability using a 10-fold cross-validation, a permutation test, and test data sets. A wide range of cross-validation error rates was found (from 7.5% to 16.3% for the largest trainings set and from 0% to 60% for the smallest training set) and the error rate increased when the number of subjects decreased. The test error rates varied from 5% to 50%. The smaller the number of subjects compared to the number of variables, the less the outcome of validation tools such as cross-validation, jack-knifing model parameters and permutation tests can be trusted. The result depends crucially on the specific sample of subjects that is used for modelling. The validation tools cannot be used as warning mechanism for problems due to sample size or to representativity of the sampling.