Reduced glycemic index and glycemic load diets do not increase the effects of energy restriction on weight loss and insulin sensitivity in obese men and women

Low glycaemic index and glycaemic load diets in adults with excess weight: Systematic review and meta-analysis of randomised clinical trials

BACKGROUND

To compare the effects of low and high glycaemic index/glycaemic load (GI/GL) diets on body weight in adults with excess weight.

METHODS

We searched for randomised controlled trials comparing low GI/GL vs. high GI/GL diets from Medline (via PubMed), Embase, Scopus and Web of Science. The variables of interest were anthropometric measurements, fasting glucose and fasting insulin levels and lipid profile, and 10 studies were included in the meta-analysis.

RESULTS

The sample size ranged from 19 to 203 participants. Low GI/GL is not superior to high GI/GL diets on body weight reduction in adults with excess weight (body mass index [BMI] ≥ 25 kg m^-2 ). However, low GI/GL diets show greater body weight reductions in adults with BMI ≥ 30 kg m^-2 (-0.93 kg; 95% confidence interval [CI] = -1.73 to -0.12; p = 0.045). Compared with high GI/GL diets, low GI/GL diets may also help reduce fasting glucose (-1.97 mg dl^-1 ; 95% CI = -3.76 to 0.19; p = 0.030) and fasting insulin (-0.55 µU ml^-1 ; 95% CI = -0.95 to -0.15; p = 0.007). No differences in fat mass, fat-free mass, waist circumference and lipid profile were observed between low GI/GL and high GI/GL diets. The risk of bias for body weight was classified as 'low risk' (25% of the studies) and 'some concerns' for all domains of RoB 2 tool in most studies.

CONCLUSIONS

When compared with high GI/GL diets, low GI/GL diets appear to more effectively reduce fasting glucose and insulin and promote greater body weight reduction in adults with obesity (BMI ≥ 30 kg m^-2 ).

Isocaloric-restricted Mediterranean Diet and Chinese Diets High or Low in Plants in Adults With Prediabetes

CONTEXT

Calorie restriction plus dietary advice is suggested as a preventive strategy for individuals with obesity and prediabetes; however, optimal diet is still debatable. We aimed to compare the effects of Mediterranean diet (MD) and Chinese diets high or low in plants on body weight and glucose homeostasis among high-risk Chinese.

SUBJECTS AND METHODS

In this parallel-arm randomized controlled trial, 253 Chinese adults aged 25 to 60 years with a body mass index ≥ 24.0 kg/m2 and fasting blood glucose ≥ 5.6 mmol/L were randomly assigned to 3 isocaloric-restricted diets: MD (n = 84), a traditional Jiangnan diet high in plants (TJD, n = 85), or a control diet low in plants (CD, n = 84). During the 6-month trial, a 5-weekday full-feeding regimen was followed, along with mobile app-based monitoring. Abdominal fat measurement (magnetic resonance imaging), oral glucose tolerance test (OGTT), and continuous glucose monitoring (CGM) were conducted at baseline and 3 and 6 months.

RESULTS

With a 25% calorie restriction for 6 months, weight deduction was 5.72 kg (95% confidence interval, 5.03-6.40) for MD, 5.05 kg (4.38-5.73) for TJD, and 5.38 kg (4.70-6.06) for CD (Ptime < 0.0001). No between-group differences were found for fasting glucose, insulin, and the Matsuda index from OGTT. Notably, CD had significantly longer time below range (glucose < 3.9 mmol/L) than MD (0.81% [0.21-1.40], P = 0.024) and marginally longer time than TJD (0.56% [-0.03 to 1.15], P = 0.065), as measured by CGM.

CONCLUSIONS

With the 6-month isocaloric-restricted feeding, TJD and MD achieved comparable weight deduction and improved glucose homeostasis, whereas CD showed a higher risk for hypoglycemia.

Dietary Glycemic Index and Load and the Risk of Type 2 Diabetes: Assessment of Causal Relations

While dietary factors are important modifiable risk factors for type 2 diabetes (T2D), the causal role of carbohydrate quality in nutrition remains controversial. Dietary glycemic index (GI) and glycemic load (GL) have been examined in relation to the risk of T2D in multiple prospective cohort studies. Previous meta-analyses indicate significant relations but consideration of causality has been minimal. Here, the results of our recent meta-analyses of prospective cohort studies of 4 to 26-y follow-up are interpreted in the context of the nine Bradford-Hill criteria for causality, that is: (1) Strength of Association, (2) Consistency, (3) Specificity, (4) Temporality, (5) Biological Gradient, (6) Plausibility, (7) Experimental evidence, (8) Analogy, and (9) Coherence. These criteria necessitated referral to a body of literature wider than prospective cohort studies alone, especially in criteria 6 to 9. In this analysis, all nine of the Hill's criteria were met for GI and GL indicating that we can be confident of a role for GI and GL as causal factors contributing to incident T2D. In addition, neither dietary fiber nor cereal fiber nor wholegrain were found to be reliable or effective surrogate measures of GI or GL. Finally, our cost-benefit analysis suggests food and nutrition advice favors lower GI or GL and would produce significant potential cost savings in national healthcare budgets. The high confidence in causal associations for incident T2D is sufficient to consider inclusion of GI and GL in food and nutrient-based recommendations.

Low glycaemic index diets as an intervention for obesity: a systematic review and meta-analysis

OBJECTIVES

Low glycaemic index (GI) diets may aid in weight loss by reducing postprandial blood glucose excursions, leading to more stable blood glucose concentrations and therefore a reduction in hunger. To test this hypothesis, we conducted a systematic review and meta-analysis of randomized controlled trials comparing low GI diets with other diet types.

METHODS

We included 101 studies involving 109 study arms and 8,527 participants. We meta-analysed the studies using a random-effects model and conducted subgroup analyses and meta-regression based on control diet, blood glucose control, baseline BMI and dietary GI.

RESULTS

Low GI diets resulted in small but significant improvements in body weight, BMI, LDL and total cholesterol overall, although no individual control diet was significantly different from low GI diets. Studies in people with normal blood glucose who achieved a difference in GI of 20 points or more resulted in a larger reduction in body weight (SMD = -0.26; 95% CIs [-0.43, -0.09]), and total cholesterol (SMD = -0.24; 95% CIs [-0.42, -0.05]) than studies that only achieved a smaller reduction in GI.

CONCLUSIONS

Low GI diets, especially diets achieving a substantial decrease in GI, were moderately effective in lowering body weight. However, efforts should be made to increase compliance with low GI diets, in order for them to be effective in people with overweight and obesity.

Effects of low-fat compared with high-fat diet on cardiometabolic indicators in people with overweight and obesity without overt metabolic disturbance: a systematic review and meta-analysis of randomised controlled trials

Randomised controlled trials comparing low- v. high-fat diets on cardiometabolic risk factors in people with overweight or obesity have shown inconsistent results, which may be due to the mixed metabolic status of people with excess adiposity. The role of dietary fat manipulation in modifying cardiometabolic indicators in people with overweight or obese without metabolic disturbance is unclear. Thus, meta-analysis was conducted to compare low- v. high-fat diets on cardiometabolic indicators in people who are overweight or obese without metabolic disturbance in the present study. Databases were searched until October 2016. The pooled effects of outcomes with heterogeneity were calculated with a random-effects model, heterogeneities were analysed by subgroup and meta-regression. As a result, twenty studies with 2106 participants were included in the meta-analysis. Total cholesterol and LDL-cholesterol levels were lower following low-fat diets compared with high-fat diets: weighted mean difference (WMD) was −7·05 mg/dl (−0·18 mmol/l; 95 % CI −11·30, −2·80; P=0·001) and −4·41 mg/dl (−0·11 mmol/l; 95 % CI −7·81, −1·00; P=0·011), respectively. Conversely, significant higher level of TAG (WMD: 11·68 mg/dl (0·13 mmol/l), 95 % CI 5·90, 17·45; P<0·001) and lower level of HDL-cholesterol (WMD: −2·57 mg/dl (−0·07 mmol/l); 95 % CI −3·85, −1·28; P<0·001) were found following low-fat diets compared with high-fat diets. In conclusion, dietary fat manipulation has a significant influence on blood lipid levels in people with overweight or obesity without metabolic disturbances.

Low glycaemic index diets for the prevention of cardiovascular disease

BACKGROUND

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

OBJECTIVES

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

SEARCH METHODS

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

SELECTION CRITERIA

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

DATA COLLECTION AND ANALYSIS

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

MAIN RESULTS

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

AUTHORS' CONCLUSIONS

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

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

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

Low glycemic index diet reduces body fat and attenuates inflammatory and metabolic responses in patients with type 2 diabetes

Objective

The aim of this study was to verify the effects of glycemic index (GI) on body composition, and on inflammatory and metabolic markers concentrations in patients with type 2 diabetes.

Subjects and methods

In this randomized controlled parallel trial, twenty subjects (aged 42.4 ± 5.1 years, BMI 29.2 ± 4.8 kg.m-2) were allocated to low GI (LGI) (n = 10) or high GI (HGI) (n = 10) groups. Body composition, inflammatory and metabolic markers were assessed at baseline and after 30 days of intervention. Food intake was monitored during the study using three-day food records completed on two non-consecutive weekdays and on a weekend day.

Results

Body fat reduced after the LGI intervention compared with baseline (P = 0.043) and with the HGI group (P = 0.036). Serum fructosamine concentration (P = 0.031) and TNF-α mRNA expression (P = 0.05) increased in the HGI group. Serum non-esterified fatty acids were greater in the HGI than in the LGI group (P = 0.032). IL-6 mRNA expression tended to decrease after the consumption of the LGI diet compared to baseline (P = 0.06).

Conclusion

The LGI diet reduced body fat and prevented the negative metabolic and inflammatory responses induced by the HGI diet.

Effects of carbohydrate quantity and glycemic index on resting metabolic rate and body composition during weight loss

OBJECTIVE

To examine the effects of diets varying in carbohydrate and glycemic index (GI) on changes in body composition, resting metabolic rate (RMR), and metabolic adaptation during and after weight loss.

METHODS

Adults with obesity (n = 91) were randomized to one of four provided-food diets for 17 weeks. Diets differed in percentage energy from carbohydrate (55% or 70%) and GI (low or high) but were matched for protein, fiber, and energy. Body weight, body composition, RMR, and metabolic adaptation (measured RMR-predicted RMR) were measured during weight loss and subsequent weight stability.

RESULTS

No effect of dietary carbohydrate content or GI on body weight loss or percentage of weight lost as fat mass (FM) was observed. Measured RMR was significantly lower (-226 kJ/day [95% CI: -314 to -138 kJ/day], P < 0.001) than predicted RMR following weight loss, but this difference was attenuated after 5 weeks of weight stability. Metabolic adaptation did not differ by dietary carbohydrate content or GI and was not associated with weight regain 12 months later.

CONCLUSIONS

Moderate-carbohydrate and low-GI diets did not preferentially reduce FM, preserve lean mass, or attenuate metabolic adaptation during weight loss compared to high-carbohydrate and high-GI diets.

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

IMPORTANCE

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

OBJECTIVE

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

DESIGN, SETTING, AND PARTICIPANTS

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

INTERVENTIONS

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

MAIN OUTCOMES AND MEASURES

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

RESULTS

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

CONCLUSIONS AND RELEVANCE

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

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00608049.

Low carbohydrate versus isoenergetic balanced diets for reducing weight and cardiovascular risk: a systematic review and meta-analysis

BACKGROUND

Some popular weight loss diets restricting carbohydrates (CHO) claim to be more effective, and have additional health benefits in preventing cardiovascular disease compared to balanced weight loss diets.

METHODS AND FINDINGS

We compared the effects of low CHO and isoenergetic balanced weight loss diets in overweight and obese adults assessed in randomised controlled trials (minimum follow-up of 12 weeks), and summarised the effects on weight, as well as cardiovascular and diabetes risk. Dietary criteria were derived from existing macronutrient recommendations. We searched Medline, EMBASE and CENTRAL (19 March 2014). Analysis was stratified by outcomes at 3-6 months and 1-2 years, and participants with diabetes were analysed separately. We evaluated dietary adherence and used GRADE to assess the quality of evidence. We calculated mean differences (MD) and performed random-effects meta-analysis. Nineteen trials were included (n = 3209); 3 had adequate allocation concealment. In non-diabetic participants, our analysis showed little or no difference in mean weight loss in the two groups at 3-6 months (MD 0.74 kg, 95%CI -1.49 to 0.01 kg; I2 = 53%; n = 1745, 14 trials; moderate quality evidence) and 1-2 years (MD 0.48 kg, 95%CI -1.44 kg to 0.49 kg; I2 = 12%; n = 1025; 7 trials, moderate quality evidence). Furthermore, little or no difference was detected at 3-6 months and 1-2 years for blood pressure, LDL, HDL and total cholesterol, triglycerides and fasting blood glucose (>914 participants). In diabetic participants, findings showed a similar pattern.

CONCLUSIONS

Trials show weight loss in the short-term irrespective of whether the diet is low CHO or balanced. There is probably little or no difference in weight loss and changes in cardiovascular risk factors up to two years of follow-up when overweight and obese adults, with or without type 2 diabetes, are randomised to low CHO diets and isoenergetic balanced weight loss diets.

Carbohydrate quality and quantity affect glucose and lipid metabolism during weight regain in healthy men

In this controlled, parallel-group feeding trial, we examined the impact of carbohydrate (CHO) intake and glycemic index (GI) on glucose and lipid metabolism during refeeding after weight loss. Healthy men (n = 32 total, age: 25.5 ± 3.9 y, BMI: 23.5 ± 2.0 kg/m2) overconsumed diets containing either 50% or 65% CHO for 1 wk (+50% of energy requirements) and then underwent 3 wk of calorie restriction (CR; -50%) followed by 2 wk of overconsuming (refeeding, +50%) the same diet but with either a low or high GI (40 vs.70 during CR, 41 vs.74 during refeeding) so that glycemic load (GL; dietary CHO content x GI) differed between groups during all phases. Glucose profiles were assessed by continuous interstitial glucose monitoring, insulin sensitivity (IS) by fasting blood sampling, oral glucose tolerance test (OGTT) and hyperinsulinemic-euglycemic clamp, and liver fat by MRI. Daytime area under the curve-glucose during refeeding was higher with high compared with low GI (P = 0.01) and 65% compared with 50% CHO intake (P = 0.05) and correlated with dietary GL (r = 0.71; P < 0.001). IS increased with CR and decreased again with refeeding in all groups. The decrease in OGTT-derived IS was greater with high- than with low-GI diets (-41 vs. -15%; P-interaction = 0.01) and correlated with dietary GL during refeeding (r = -0.51; P < 0.01). Serum triglycerides (TGs) and liver fat also improved with CR (-17 ± 38 mg/dL and -1.1 ± 1.3%; P < 0.05 and <0.001) and increased again with refeeding (+48 ± 48 mg/dL and +2.2 ± 1.6%; P < 0.001). After refeeding, serum TGs and liver fat were elevated above baseline values with 65% CHO intake only (+59.9 ± 37.5 mg/dL and +1.1 ± 1.7%, P-interaction <0.001 and <0.05). In conclusion, a diet low in GI and moderate in CHO content (i.e., low GL) may have health benefits by positively affecting daylong glycemia, IS, and liver fat.

Long-term effects of low glycemic index/load vs. high glycemic index/load diets on parameters of obesity and obesity-associated risks: a systematic review and meta-analysis

AIM

The aim of the present meta-analysis was to investigate the long-term effects of glycemic index-related diets in the management of obesity with a special emphasis on the potential benefits of low glycemic index/load (GI/GL) in the prevention of obesity-associated risks.

DATA SYNTHESIS

Electronic searches for randomized controlled trials (RCTs) comparing low glycemic index/load versus high glycemic index/load diets were performed in MEDLINE, EMBASE and the Cochrane Library. Outcome of interest markers included anthropometric data as well as biomarkers of CVD and glycemic control. Study specific weighted mean differences were pooled using a random effect model. 14 studies were included in the primary meta-analysis. Weighted mean differences in change of C-reactive protein [WMD: -0.43 mg/dl, (95% CI -0.78 to -0.09), p = 0.01], and fasting insulin [WMD: -5.16 pmol/L, (95% CI -8.45 to -1.88), p = 0.002] were significantly more pronounced in benefit of low GI/GL diets. However decrease in fat free mass [WMD: -1.04 kg (95% CI -1.73 to -0.35), p = 0.003] was significantly more pronounced following low GI/GL diets as well. No significant changes were observed for blood lipids, anthropometric measures, HbA1c and fasting glucose. Sensitivity analysis was performed for RCTs excluding subjects with type 2 diabetes. Decreases in C-reactive protein and fasting insulin remained statistically significant in the low GI/GL subgroups.

CONCLUSIONS

The present systematic review provides evidence for beneficial effects of long-term interventions administering a low glycemic index/load diet with respect to fasting insulin and pro-inflammatory markers such as C-reactive protein which might prove to be helpful in the primary prevention of obesity-associated diseases.

Molecular weight of barley β-glucan influences energy expenditure, gastric emptying and glycaemic response in human subjects

Barley β-glucan (BG) has been shown to reduce glycaemic response (GR) in some studies. It is hypothesised that this reduction may be a function of its physical properties that delay gastric emptying (GE). The effect of these changes in GR and GE on diet-induced thermogenesis (DIT) is not known. The aim of the present study was to assess the effect of BG of different molecular weights and purities on GR, GE and DIT in healthy subjects. This was a randomised, single-blind, repeated-measures design where fifteen healthy subjects were tested on three occasions following an overnight fast. Following the baseline measurements, the volunteers were fed a soup containing high-molecular-weight BG (HBG), a soup containing low-molecular-weight BG (LBG) or a control soup with no BG (CHO). Following the consumption of the breakfast, GR was measured using finger-prick blood samples, GE was determined using the 13C-octanoic acid breath test and DIT was measured using indirect calorimetry. There was a difference in GR AUC between the soups after 60 min but not after 120 min. The CHO and LBG meals had a greater GR than the HBG meal. There were differences in all GE time points, with the HBG meal having the slowest GE time. There was a correlation between the GR and the initial GE times. There were differences in total DIT between the three test meals with the HBG meal having the lowest DIT. The present study indicates that HBG has the ability to delay GE due to increased viscosity, resulting in a decreased GR and DIT.

Effect of diets differing in glycemic index and glycemic load on cardiovascular risk factors: review of randomized controlled-feeding trials

Despite a considerable amount of data available on the relationship between dietary glycemic index (GI) or load (GL) and cardiovascular disease (CVD) risk factors, in aggregate, the area remains unsettled. The aim of the present review was to summarize the effect of diets differing in GI/GL on CVD risk factors, by examining randomized controlled-feeding trials that provided all food and beverages to adult participants. The studies included a low and high GI/GL diet phase for a minimum of four weeks duration, and reported at least one outcome related to CVD risk; glucose homeostasis, lipid profile or inflammatory status. Ten publications representing five trials were identified. The low GI/GL compared to the high GI/GL diet unexpectedly resulted in significantly higher fasting glucose concentrations in two of the trials, and a lower area under the curve for glucose and insulin in one of the two studies during an oral glucose tolerance test. Response of plasma total, low density lipoprotein and high density lipoprotein cholesterol concentrations was conflicting in two of the studies for which data were available. There was either weak or no effect on inflammatory markers. The results of the five randomized controlled trials satisfying the inclusion criteria suggest inconsistent effects of the GI/GL value of the diet on CVD risk factors.

Low glycaemic index diets and blood lipids: a systematic review and meta-analysis of randomised controlled trials

AIMS

Low glycaemic index (GI) diets are beneficial in the management of hyperglycemia. Cardiovascular diseases are the major cause of mortality in diabetes therefore it is important to understand the effects of GI on blood lipids. The aim was to systematically review randomised controlled trials (RCTs) of low GI diets on blood lipids.

DATA SYNTHESIS

We searched OVID Medline, Embase and Cochrane library to March 2012. Random effects meta-analyses were performed on twenty-eight RCTs comparing low- with high GI diets over at least 4 weeks (1272 participants; studies ranged from 6 to 155 participants); one was powered on blood lipids, 3 had adequate allocation concealment. Low GI diets significantly reduced total (-0.13 mmol/l, 95%CI -0.22 to -0.04, P = 0.004, 27 trials, 1441 participants, I(2) = 0%) and LDL-cholesterol (-0.16 mmol/l, 95%CI -0.24 to -0.08, P < 0.0001, 23 trials, 1281 participants, I(2) = 0%) compared with high GI diets and independently of weight loss. Subgroup analyses suggest that reductions in LDL-C are greatest in studies of shortest duration and greatest magnitude of GI reduction. Furthermore, lipid improvements appear greatest and most reliable when the low GI intervention is accompanied by an increase in dietary fibre. Sensitivity analyses, removing studies without adequate allocation concealment, lost statistical significance but retained suggested mean falls of ~0.10 mmol/l in both. There were no effects on HDL-cholesterol (MD -0.03 mmol/l, 95%CI -0.06 to 0.00, I(2) = 0%), or triglycerides (MD 0.01 mmol/l, 95%CI -0.06 to 0.08, I(2) = 0%).

CONCLUSIONS

This meta-analysis provides consistent evidence that low GI diets reduce total and LDL-cholesterol and have no effect on HDL-cholesterol or triglycerides.

Beneficial effects of a high-protein, low-glycemic-load hypocaloric diet in overweight and obese women with polycystic ovary syndrome: a randomized controlled intervention study

OBJECTIVE

The recommended composition of a hypocaloric diet for obese women with polycystic ovary syndrome (PCOS) is unclear. The aim of this study was to investigate the effects of a high-protein, low-glycemic-load diet compared with a conventional hypocaloric diet on reproductive hormones, inflammatory markers, lipids, glucose, and insulin levels in obese women with PCOS.

METHODS

A total of 60 overweight and obese women with PCOS who did not use insulin-sensitizing agents were recruited and randomly assigned to 1 of the 2 hypocaloric diet groups for a single-blind clinical trial. The groups included a conventional hypocaloric diet (CHCD) (15% of daily energy from protein) and a modified hypocaloric diet (MHCD) with a high-protein, low-glycemic load (30% of daily energy from protein plus low-glycemic-load foods selected from a list) that was prescribed via counseling visits weekly during 12 weeks of study. Anthropometric assessments and biochemical measurements including reproductive hormones, inflammatory factors, lipids, glucose, and insulin were performed on fasting blood samples at baseline and after 12 weeks of dietary intervention.

RESULTS

Weight loss was significant and similar in the 2 groups. Mean of testosterone in the MHCD and CHCD groups decreased from 1.78 ± 0.32 to 1.31 ± 0.26 ng/ml and from 1.51 ± 0.12 to 1.15 ± 0.11 ng/ml, respectively (p < 0.001). Follicle sensitizing hormone (FSH), luteinizing hormone (LH), and blood lipids concentrations were not changed except low-density lipoprotein cholesterol (LDL-C) was reduced by 24.5% ± 12.3% (p < 0.001 for both) after 12 weeks of intervention. MHCD resulted in a significant reduction in insulin level, homeostatic model assessment for insulin resistance (HOMA), and high-sensitivity C- reactive protein (hsCRP) concentration (p < 0.001).

CONCLUSIONS

In this study both hypocaloric diets significantly led to reduced body weight and androgen levels in these two groups of women with PCOS. The combination of high-protein and low-glycemic-load foods in a modified diet caused a significant increase in insulin sensitivity and a decrease in hsCRP level when compared with a conventional diet.

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

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

Body composition, dietary composition, and components of metabolic syndrome in overweight and obese adults after a 12-week trial on dietary treatments focused on portion control, energy density, or glycemic index

BACKGROUND

Given the rise in obesity and associated chronic diseases, it is critical to determine optimal weight management approaches that will also improve dietary composition and chronic disease risk factors. Few studies have examined all these weight, diet, and disease risk variables in subjects participating in recommended multi-disciplinary weight loss programs using different dietary strategies.

METHODS

This study compared effects of three dietary approaches to weight loss on body composition, dietary composition and risk factors for metabolic syndrome (MetS). In a 12-week trial, sedentary but otherwise healthy overweight and obese adults (19 M & 138 F; 38.7±6.7 y; BMI 31.8±2.2) who were attending weekly group sessions for weight loss followed either portion control, low energy density, or low glycemic index diet plans. At baseline and 12 weeks, measures included anthropometrics, body composition, 3-day food diaries, blood pressure, total lipid profile, HOMA, C-reactive protein, and fasting blood glucose and insulin. Data were analyzed by repeated measures analysis of variance.

RESULTS

All groups significantly reduced body weight and showed significant improvements in body composition (p<0.001), and components of metabolic syndrome (p<0.027 to 0.002), although HDL decreased (p<0.001). Dietary energy, %fat and %saturated fat decreased while protein intake increased significantly (p<0.001). There were no significant differences among the three groups in any variable related to body composition, dietary composition, or MetS components.

CONCLUSION

Different dietary approaches based on portion control, low energy density, or low glycemic index produced similar, significant short-term improvements in body composition, diet compositin, and MetS components in overweight and obese adults undergoing weekly weight loss meetings. This may allow for flexibility in options for dietary counseling based on patient preference.

Caloric restriction induces changes in insulin and body weight measurements that are inversely associated with subsequent weight regain

BACKGROUND

Successful weight maintenance following weight loss is challenging for many people. Identifying predictors of longer-term success will help target clinical resources more effectively. To date, focus has been predominantly on the identification of predictors of weight loss. The goal of the current study was to determine if changes in anthropometric and clinical parameters during acute weight loss are associated with subsequent weight regain.

METHODOLOGY

The study consisted of an 8-week low calorie diet (LCD) followed by a 6-month weight maintenance phase. Anthropometric and clinical parameters were analyzed before and after the LCD in the 285 participants (112 men, 173 women) who regained weight during the weight maintenance phase. Mixed model ANOVA, Spearman correlation, and linear regression were used to study the relationships between clinical measurements and weight regain.

PRINCIPAL FINDINGS

Gender differences were observed for body weight and several clinical parameters at both baseline and during the LCD-induced weight loss phase. LCD-induced changes in BMI (Spearman's ρ = 0.22, p = 0.0002) were inversely associated with weight regain in both men and women. LCD-induced changes in fasting insulin (ρ = 0.18, p = 0.0043) and HOMA-IR (ρ = 0.19, p = 0.0023) were also associated independently with weight regain in both genders. The aforementioned associations remained statistically significant in regression models taking account of variables known to independently influence body weight.

CONCLUSIONS/SIGNIFICANCE

LCD-induced changes in BMI, fasting insulin, and HOMA-IR are inversely associated with weight regain in the 6-month period following weight loss.

Effects of tea combined with high-protein meal replacement shakes on anthropometric measurements, lipid profiles, cellular biochemistry, neurochemistry, and microbial metabolism: a prospective observational study

OBJECTIVE

The purpose of this study was to report preliminary data on the effects of tea and high-protein meal replacement shakes on weight loss, waist-to-hip ratios, and lipid profiles in healthy subjects. Secondary analyses of urine samples assessed pre-post changes in cellular biochemistry, neurochemistry, and microbial metabolism.

METHODS

This study used a pre-post intervention design without a control group. Thirty healthy subjects (20-60 years of age; 23 women and 7 men) participated in a 28-day diet intervention program consisting of a cleansing day and 6 restricted diet days per week. On cleansing days, the subjects drank 4 oz of tea 4 times per day with a recommendation to drink at least 64 oz of filtered water. On the restricted diet days, the subjects drank 2 high-protein meal replacement shakes, consumed one 400- to 600-cal (1674.3-2511.5 joules) meal consisting of low-glycemic index foods, and drank at least 64 oz of filtered water.

RESULTS

Multiple paired t tests detected reductions in weight (6.4 lb), waist (1.9 in), and hip (1.1 in) measurements and in total cholesterol (13.3 mg/dL) and low-density lipoprotein cholesterol (11.4 mg/dL) (P < .05). Multiple paired t tests detected significant increases in energy metabolism from carbohydrates and amino acids and concomitant increases in oxidative stress (P < .05).

CONCLUSION

The data support the concept that a low-glycemic load diet intervention incorporating tea and high-protein meal replacement shakes may cause weight loss and improve lipid profiles. The significant physiologic changes from the urine samples did not reflect meaningful metabolic effects.

Decreases in dietary glycemic index are related to weight loss among individuals following therapeutic diets for type 2 diabetes

This study assessed the effect of changes in glycemic index (GI) and load (GL) on weight loss and glycated hemoglobin (HbA1c) among individuals with type 2 diabetes beginning a vegan diet or diet following the 2003 American Diabetes Association (ADA) recommendations. The study was a 22-wk, randomized trial of 99 participants with type 2 diabetes who were counseled to follow 1 of 2 diet treatments. GI and GL changes were assessed based on 3-d dietary records. The relationships between GI/GL and changes in weight and HbA1C were calculated. In an intention-to-treat analysis (n = 99), the vegan group reduced GI to a greater extent than the ADA group (P < 0.05), but GL was reduced further in the ADA than the vegan group (P < 0.001). GI predicted changes in weight (P = 0.001), adjusting for changes in fiber, carbohydrate, fat, alcohol, energy intake, steps per day, group, and demographics, such that for every point decrease in GI, participants lost ~0.2 kg (0.44 lb). GI was not a predictor for changes in HbA1C after controlling for weight loss (P = 0.33). Weight loss was a predictor of changes in HbA1C (P = 0.047). GL was not related to weight loss or changes in HbA1C. A low-GI diet appears to be one of the determinants of success of a vegan or ADA diet in reducing body weight among people with type 2 diabetes. The reduction of body weight, in turn, was predictive of decreasing HbA1C.

Targeting dietary fat or glycemic load in the treatment of obesity and type 2 diabetes: a randomized controlled trial

AIMS

To compare the effects of lifestyle modification programs that prescribe low-glycemic load (GL) vs. low-fat diets in a randomized trial.

METHODS

Seventy-nine obese adults with type 2 diabetes received low-fat or low-GL dietary instruction, delivered in 40-week lifestyle modification programs with identical goals for calorie intake and physical activity. Changes in weight, HbA(1c), and other metabolic parameters were compared at weeks 20 and 40.

RESULTS

Weight loss did not differ between groups at week 20 (low-fat: -5.7±3.7%; low-GL: -6.7±4.4%, p=.26) or week 40 (low-fat: -4.5±7.5%; low-GL: -6.4±8.2%, p=.28). Adjusting for changes in antidiabetic medications, subjects on the low-GL diet had larger reductions in HbA(1c) than those on the low-fat diet at week 20 (low-fat: -0.3±0.6%; low-GL: -0.7±0.6%, p=.01), and week 40 (low-fat: -0.1±1.2%; low-GL: -0.8±1.3%; p=.01). Groups did not differ significantly on any other metabolic outcomes (p≥.06).

CONCLUSIONS

Results suggest that targeting GL, rather than dietary fat, in a low-calorie diet can significantly enhance the effect of weight loss on HbA(1c) in patients with type 2 diabetes.

Anti-inflammatory nutrition as a pharmacological approach to treat obesity

Obesity is a multifactorial condition resulting from improper balances of hormones and gene expression induced by the diet. Obesity also has a strong inflammatory component that can be driven by diet-induced increases in arachidonic acid. The purpose of this paper is to discuss the molecular targets that can be addressed by anti-inflammatory nutrition. These molecular targets range from reduction of proinflammatory eicosanoids to the modulation of features of the innate immune system, such as toll-like receptors and gene transcription factors. From knowledge of the impact of these dietary nutrients on these various molecular targets, it becomes possible to develop a general outline of an anti-inflammatory diet that can offer a unique synergism with more traditional pharmacological approaches in treating obesity and its associated comorbidities.

The effect of a fibre supplement compared to a healthy diet on body composition, lipids, glucose, insulin and other metabolic syndrome risk factors in overweight and obese individuals

Optimum levels and types of dietary fibre that provide the greatest beneficial effects on metabolic syndrome risk factors in overweight and obese individuals have yet to be determined in clinical trials. The present parallel design study compared the effects of fibre intake from a healthy dietv. a fibre supplement (psyllium) or a healthy diet plus fibre supplement on fasting lipids, glucose, insulin and body composition. Overweight/obese adults were randomised to either control (with placebo), fibre supplement (FIB), healthy eating plus placebo (HLT) or healthy eating plus fibre supplement (HLT–FIB). There was a significant increase in fibre intake in HLT–FIB, HLT and FIB groups up to 59, 31 and 55 g, respectively, at 12 weeks when compared to control (20 g). Weight, BMI and % total body fat were significantly reduced in FIB and HLT–FIB groups, with weight and BMI significantly reduced in the HLT group compared with control at 12 weeks. HLT–FIB and HLT groups had significant reductions in TAG and insulin compared with control at 6 and 12 weeks, and in insulin compared with the FIB group at 12 weeks. The HLT–FIB, HLT and FIB groups all had significant reductions in total cholesterol and LDL-cholesterol compared with control after 6 and 12 weeks. The present study demonstrated that simply adding psyllium fibre supplementation to a normal diet was sufficient to obtain beneficial effects in risk factors. However, a high-fibre diet consisting of a psyllium supplement plus fibre from a healthy diet provided the greatest improvements in metabolic syndrome risk factors.

[Nonsurgical management of obesity in adults]

General practitioners are placed in an ideal position to manage obesity. First, they have to consider the motivation of the obese patient to change his habits. When the patient is not motivated to loss weight, their role is to identify and treat co-morbidities, to evaluate the risk related to the obesity and to establish a therapeutic diagnosis to evaluate motivation and ability to change. If the patient is motivated, the therapeutic choices have to be adapted individually to each patient. An inadequate management may not only result in a failure but may increase obesity. The objectives in obesity treatment are to achieve weight loss in order to reduce health risk as far as possible, to maintain that weight loss, to restore quality of life. Goals and methods must be realistic. Even a modest weight loss (5-10 % of initial weight) will improve health indices in an obese patient. Dietary treatment and physical activity are fundamental to the management of obesity. Compliance with the diet is the major problem, especially during the phase of weight maintenance after the excess weight loss has been lost. Initial weight reduction depends on the level of energy deficit and weight maintenance on compliance to a low fat diet and a physical activity programme. Cognitive behavioural approaches should be an integral part of the management of a chronic disease. This treatment is very useful to improve body image, self-esteem, management of stress and control of disordered eating patterns. A psychotherapeutic approach is often necessary, especially when the obesity is psycho-determined. Obesity drugs should be used for carefully selected patients, as an adjunct to diet therapy and lifestyle modifications, under medical supervision.

Dietary starch type affects body weight and glycemic control in freely fed but not energy-restricted obese rats

This study comprised 2 experiments that tested the hypothesis that a high-amylose starch diet (AMO) would improve body weight and glycemic control relative to a high-amylopectin starch diet (AMN) in rats with diet-induced obesity. After inducing obesity with a high-fat and -energy diet (Expt. 1), male Sprague-Dawley rats (n = 46) were divided into 4 groups and given free or restricted access to either an AMN or an AMO diet for 4 wk (Expt. 2). After 3 wk, rats from each group underwent an oral glucose tolerance test. At the end of the experiment, food-deprived rats were killed by decapitation and blood and tissues were collected for analyses. AMO led to lower total energy intake, weight gain, fat pad mass, and glycemic response but higher insulin sensitivity index than AMN, only when consumed ad libitum (AL) (P < 0.05). AMO led to higher glucagon-like peptide-1 and peptide YY responses and mRNA levels, independent of feeding paradigm (P < 0.01). The mRNA levels of key neuropeptide systems involved in the regulation of food intake were affected only by energy restriction. On the other hand, AMO resulted in higher expression of uncoupling protein-1 in the brown adipose tissue than AMN in rats that consumed food AL (P < 0.05). The effects of AMO appear to be mediated by its high resistant starch content rather than its glycemic index. We conclude that starches high in AMO can be effective in weight and glycemic control in obesity.

Acute effects of dietary glycemic index on antioxidant capacity in a nutrient-controlled feeding study

Oxidative stress, caused by an imbalance between antioxidant capacity and reactive oxygen species, may be an early event in a metabolic cascade elicited by a high glycemic index (GI) diet, ultimately increasing the risk for cardiovascular disease and diabetes. We conducted a feeding study to evaluate the acute effects of low-GI compared with high-GI diets on oxidative stress and cardiovascular disease risk factors. The crossover study comprised two 10-day in-patient admissions to a clinical research center. For the admissions, 12 overweight or obese (BMI: 27-45 kg/m(2)) male subjects aged 18-35 years consumed low-GI or high-GI diets controlled for potentially confounding nutrients. On day 7, after an overnight fast and then during a 5-h postprandial period, we assessed total antioxidant capacity (total and perchloric acid (PCA) protein-precipitated plasma oxygen radical absorbance capacity (ORAC) assay) and oxidative stress status (urinary F(2alpha)-isoprostanes (F(2)IP)). On day 10, we measured cardiovascular disease risk factors. Under fasting conditions, total antioxidant capacity was significantly higher during the low-GI vs. high-GI diet based on total ORAC (11,736 +/- 668 vs. 10,381 +/- 612 micromol Trolox equivalents/l, P = 0.002) and PCA-ORAC (1,276 +/- 96 vs. 1,210 +/- 96 micromol Trolox equivalents/l, P = 0.02). Area under the postprandial response curve also differed significantly between the two diets for total ORAC and PCA-ORAC. No diet effects were observed for the other variables. Enhancement in plasma total antioxidant capacity occurs within 1 week on a low-GI diet, before changes in other risk factors, raising the possibility that this phenomenon may mediate, at least in part, the previously reported effects of GI on health.

Is there a role for the glycemic index in coronary heart disease prevention or treatment?

The clinical application of the glycemic index (GI) to the prevention and treatment of chronic diseases is controversial. No evidence exists for the implementation of low-GI diets for a reduction in coronary heart disease (CHD) mortality, events, or morbidity. Observational studies report conflicting evidence on the role of low-GI diets in CHD and risk factors for CHD. Randomized clinical trials report a small reduction in total cholesterol (-6.6 mg/dL) from low-GI diets compared with high-GI diets, but no reduction in other risk factors, such as low-density lipoprotein or high-density lipoprotein cholesterol, triglycerides, fasting glucose, insulin, or body weight. Currently, the research suggests a minimal role for the implementation of low-GI diets in the prevention or treatment of CHD.

The dietary treatment of obesity

Dietary modulation is an essential part of weight loss and maintaining its reduction. Although simple in behavioral terms (eat less, exercise more), the tremendous difficulty of weight loss and maintenance has inspired many different diet regimens, in search of an easier, more efficient way to lose weight. Contemporary issues in this matter are the composition of diets (low fat versus low carbohydrate), the choice of carbohydrate (the glycemic index), and the role of calcium and dairy products. This article discusses the scientific evidence of the various dietary manipulations for weight loss and the challenges of maintaining a reduced obese state.

Carbohydrate intake and obesity

The prevalence of obesity has increased rapidly worldwide and the importance of considering the role of diet in the prevention and treatment of obesity is widely acknowledged. This paper reviews data on the effects of dietary carbohydrates on body fatness. Does the composition of the diet as related to carbohydrates affect the likelihood of passive over-consumption and long-term weight change? In addition, methodological limitations of both observational and experimental studies of dietary composition and body weight are discussed. Carbohydrates are among the macronutrients that provide energy and can thus contribute to excess energy intake and subsequent weight gain. There is no clear evidence that altering the proportion of total carbohydrate in the diet is an important determinant of energy intake. However, there is evidence that sugar-sweetened beverages do not induce satiety to the same extent as solid forms of carbohydrate, and that increases in sugar-sweetened soft drink consumption are associated with weight gain. Findings from studies on the effect of the dietary glycemic index on body weight have not been consistent. Dietary fiber is associated with a lesser degree of weight gain in observational studies. Although it is difficult to establish with certainty that fiber rather than other dietary attributes are responsible, whole-grain cereals, vegetables, legumes and fruits seem to be the most appropriate sources of dietary carbohydrate.

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

BACKGROUND

Clinical trials of low-fat diets characteristically produce small mean long-term weight loss but a large interindividual variation in response. This variation has been attributed to psychological and behavioral factors, although biological differences may also play a role.

OBJECTIVE

The objective was to determine whether physiologic differences in insulin secretion explain differences in weight gain among individuals consuming low- and high-fat diets.

DESIGN

Of 276 individuals followed in the Quebec Family Study for a mean of 6 y, we compared those in the lowest with those in the highest dietary fat tertiles. We performed oral-glucose-tolerance tests at baseline and examined the insulin concentration at 30 min (insulin-30) as a proxy measure of insulin secretion. Six-year changes in body weight and waist circumference were the primary endpoints. We determined the associations between insulin-30 and the primary endpoints by linear regression analysis, with adjustment for potentially confounding factors.

RESULTS

Mean changes in body weight and waist circumference did not differ significantly between the lowest- and highest-fat diet groups. However, these endpoints were strongly associated with insulin-30, especially among individuals consuming the lowest-fat diet. Insulin-30 at baseline was significantly associated with 6-y weight gain (r = 0.51, P < 0.0001) and change in waist circumference (r = 0.55, P < 0.0001) in the lowest diet fat, group [corrected], but not in the highest diet fat group (r = 0.18, P = 0.086 and r = 0.20, P = 0.058, respectively) [corrected] Individuals in the highest insulin-30 and lowest dietary fat group gained 1.8 kg more than did those in the highest insulin-30 and highest dietary fat group (51%; P = 0.034); they gained 4.5 kg more than did those in the lowest insulin-30 and lowest dietary fat group (6.5-fold; P = 0.0026).

CONCLUSION

A proxy measure of insulin secretion strongly predicts changes in body weight and waist circumference over 6 y in adults, especially among those consuming lower-fat diets, which demonstrates the existence of a novel diet-phenotype interaction.

No effect of a diet with a reduced glycaemic index on satiety, energy intake and body weight in overweight and obese women

OBJECTIVE

To investigate whether a diet with a reduced glycaemic index (GI) has effects on appetite, energy intake, body weight and composition in overweight and obese female subjects.

DESIGN

Randomized crossover intervention study including two consecutive 12-week periods. Lower or higher GI versions of key carbohydrate-rich foods (breads, breakfast cereals, rice and pasta/potatoes) were provided to subjects to be incorporated into habitual diets in ad libitum quantities. Foods intended as equivalents to each other were balanced in macronutrient composition, fibre content and energy density.

SUBJECTS

Nineteen overweight and obese women, weight-stable, with moderate hyperinsulinaemia (age: 34-65 years, body mass index: 25-47 kg m(-2), fasting insulin: 49-156 pmol l(-1)).

MEASUREMENTS

Dietary intake, body weight and composition after each 12-week intervention. Subjectively rated appetite and short-term ad libitum energy intake at a snack and lunch meal following fixed lower and higher GI test breakfasts (GI 52 vs 64) in a laboratory setting.

RESULTS

Free-living diets differed in GI by 8.4 units (55.5 vs 63.9), with key foods providing 48% of carbohydrate intake during both periods. There were no differences in energy intake, body weight or body composition between treatments. On laboratory investigation days, there were no differences in subjective ratings of hunger or fullness, or in energy intake at the snack or lunch meal.

CONCLUSION

This study provides no evidence to support an effect of a reduced GI diet on satiety, energy intake or body weight in overweight/obese women. Claims that the GI of the diet per se may have specific effects on body weight may therefore be misleading.

Carbohydrate quantity and quality in relation to body mass index

The increased prevalence of overweight and obesity in the United States since approximately 1980 is temporally associated with an increase in carbohydrate intake, with no appreciable change in absolute intake of fat. Despite speculation that both carbohydrate quantity and quality have contributed significantly to excess weight gain, the relationship between carbohydrate intake and body mass index (BMI) is controversial. A review of relevant literature indicates that most epidemiologic studies show an inverse relationship between carbohydrate intake and BMI, even when controlling for potential confounders. These observational studies are supported by results from a number of dietary intervention studies wherein modest reductions in body weight were observed with an ad libitum, low-fat, high-carbohydrate diet without emphasis on energy restriction or weight loss. With few exceptions, high glycemic load is associated with lower BMI, even when adjusted for total energy intake. Data on the association between glycemic index and BMI are not as consistent, with more studies showing either no association or an inverse relationship, rather than a positive relationship. Whole-grain intake is generally inversely associated with BMI; refined grain intake is not. Because overall dietary quality tends to be higher for high-carbohydrate diets, a low-fat dietary strategy with emphasis on fiber-rich carbohydrates, particularly cereal fiber, may be beneficial for health and weight control.

Effect of early feed restriction on metabolic programming and compensatory growth in broiler chickens

The effect of early feed restriction on metabolic programming and compensatory growth was studied in broiler chickens. A total of 480 female 1-d-old broiler birds (Aconred) were randomly allocated to ad libitum and feed-restricted groups, each of which was replicated 6 times with 40 birds per replicate. Broilers were provided commercial diets. Feed-restricted broilers were deprived of feed for 4 h per day from 1 to 21 d of age. Effects of treatments were determined at 21 and 63 d of age. In feed-restricted birds at 21 d of age, BW, average daily gain and average daily feed intake, breast muscle (P < 0.01), carcass yield (P < 0.05), and abdominal fat (P < 0.05) were decreased. Ether extract content in breast muscle was increased (P < 0.01), whereas CP content was slightly decreased. Triiodothyronine (P < 0.01) and thyroxine (P < 0.05) were decreased in serum. Free fatty acid and very low density lipoprotein were slightly increased in serum, whereas triglyceride and glucose were decreased (P < 0.01). Activities of NADPH-generating enzymes in liver including malic dehydrogenase, isocitrate dehydrogenase, and glucose-6-phosphate remained unchanged in ad libitum birds, whereas hormone-sensitive lipase activity was increased (P < 0.01). In feed-restricted birds at 63 d of age, BW, average daily gain, average daily feed intake, carcass yield, breast muscle yield, and serum triiodothyronine and thyroxine remained as ad libitum birds, whereas abdominal fat yield was increased (P < 0.05). Ether extract content in breast muscle was decreased (P < 0.01), whereas CP content was increased (P < 0.05). Activities of NADPH-generating enzymes were significantly increased, except abdominal malic dehydrogenase and hormone-sensitive lipase activity was decreased (P < 0.01) in liver and abdominal fat. Lipoprotein lipase activity was increased (P < 0.05) in abdominal fat. In summary, feed restriction severely affected growth performance and lipid metabolism in broilers in the early period. Because there was no statistical difference among the final BW, near full compensatory growth was achieved. In addition, early feed restriction might have induced prolonged metabolic programming in chicks and led to adult obesity.

Is the fructose index more relevant with regards to cardiovascular disease than the glycemic index?

The glycemic index (G.I.) is a means for categorizing carbohydrates based on their ability to raise blood glucose, subsequently this index has been popularized as a way for selecting foods to reduce the risk for obesity, diabetes, and cardiovascular disease. We suggest that the G.I. is better aimed at identifying foods that stimulate insulin secretion rather than foods that stimulate insulin resistance. In this regard, fructose has a low G.I. but may be causally linked with the obesity and cardiovascular disease epidemic. The reported association of high G.I. with cardiovascular disease may be due to the association of sugar intake which contains fructose, but which has a high G.I. due to its glucose content. We propose the use of a fructose index to categorize foods and propose studies to determine the effect of low fructose diets as a means to prevent obesity, diabetes, and cardiovascular disease in the population.

Lifestyle modification for the management of obesity

Several expert panels have recommended that obese individuals attempt to lose 10% of their initial body weight through a combination of diet, physical activity, and behavior therapy (frequently referred to as lifestyle modification). This article reviews the short-and long-term results of lifestyle modification and methods to improve them. Randomized controlled trials were examined that compared different diet and activity interventions for inducing and maintaining weight loss. Studies that compared different methods of providing lifestyle modification, including on-site vs. Internet-based delivery, also were examined. A comprehensive lifestyle modification program was found to induce a loss of approximately 10% of initial weight in 16 to 26 weeks of group or individual treatment, delivered on-site. Comprehensive Internet-based programs induced a loss of approximately half this size. Patients' consumption of portion-controlled diets, including liquid meal replacements, was associated with significantly greater short-term weight loss than was the consumption of isocaloric diets comprised of conventional foods. Factors associated with long-term weight control included continued patient-practitioner contact (whether on-site or by e-mail), high levels of physical activity, and the long-term use of pharmacotherapy combined with lifestyle modification. In summary, lifestyle modification induces clinically significant weight loss that is associated with the prevention or amelioration of cardiovascular risk factors.

Long-term effects of 2 energy-restricted diets differing in glycemic load on dietary adherence, body composition, and metabolism in CALERIE: a 1-y randomized controlled trial

BACKGROUND

There remains no consensus about the optimal dietary composition for sustained weight loss.

OBJECTIVE

The objective was to examine the effects of 2 dietary macronutrient patterns with different glycemic loads on adherence to a prescribed regimen of calorie restriction (CR), weight and fat loss, and related variables.

DESIGN

A randomized controlled trial (RCT) of diets with a high glycemic load (HG) or a low glycemic load (LG) at 30% CR was conducted in 34 healthy overweight adults with a mean (+/-SD) age of 35 +/- 6 y and body mass index (kg/m(2)) of 27.6 +/- 1.4. All food was provided for 6 mo in diets controlled for confounding variables, and subjects self-administered the plans for 6 additional months. Primary and secondary outcomes included energy intake measured by doubly labeled water, body weight and fatness, hunger, satiety, and resting metabolic rate.

RESULTS

All groups consumed significantly less energy during CR than at baseline (P < 0.01), but changes in energy intake, body weight, body fat, and resting metabolic rate did not differ significantly between groups. Both groups ate more energy than provided (eg, 21% and 28% CR at 3 mo and 16% and 17% CR at 6 mo with HG and LG, respectively). Percentage weight change at 12 mo was -8.04 +/- 4.1% in the HG group and -7.81 +/- 5.0% in the LG group. There was no effect of dietary composition on changes in hunger, satiety, or satisfaction with the amount and type of provided food during CR.

CONCLUSIONS

These findings provide more detailed evidence to suggest that diets differing substantially in glycemic load induce comparable long-term weight loss.

Effects of a reduced-glycemic-load diet on body weight, body composition, and cardiovascular disease risk markers in overweight and obese adults

BACKGROUND

Lowering the dietary glycemic load and increasing protein intake may be advantageous for weight management.

OBJECTIVE

This randomized controlled trial was designed to evaluate the effects of an ad libitum reduced-glycemic-load (RGL) diet on body weight, body composition, and cardiovascular disease (CVD) risk markers in overweight and obese adults during an initial weight-loss phase (12 wk) and a weight-loss maintenance phase (weeks 24-36).

DESIGN

Subjects were assigned to RGL (n = 43) or low-fat, portion-controlled (control; n = 43) diet groups. The RGL group was instructed to eat until satisfied, maintaining a low carbohydrate intake during weeks 0-2 and adding low-glycemic-index carbohydrate thereafter. Control subjects were instructed to reduce fat intake and decrease portion sizes, with a targeted energy deficit of 500 to 800 kcal/d.

RESULTS

The RGL group had lost significantly more weight than did the control group at week 12 (-4.9 and -2.5 kg, respectively; P = 0.002), but the 2 groups did not differ significantly at week 36 (-4.5 and -2.6 kg, respectively; P = 0.085). Changes in fat mass differed between the groups at week 12 (-1.9 and -0.9 kg, respectively; P = 0.016) but not at week 36 (-2.0 and -1.3 kg, respectively; P = 0.333). At the end of the study, no differences were found in responses for CVD risk markers except a larger mean change in HDL cholesterol in the RGL group than in the control group (3.8 and 1.9 mg/dL, respectively; P = 0.037).

CONCLUSION

These findings provide evidence that an ad libitum RGL diet is a reasonable alternative to a low-fat, portion-controlled eating plan for weight management.