Influence of fat and carbohydrate proportions on the metabolic profile in patients with type 2 diabetes: a meta-analysis

The impact of food-based dietary strategies on achieving type 2 diabetes remission: A systematic review

OBJECTIVE

Conventional wisdom once asserted that diabetes was irreversible. However, contemporary research indicates that dietary changes may contribute to achieving diabetes remission in persons with type 2 diabetes (T2D). We aimed to determine the effectiveness of food-based dietary approaches for T2D remission.

METHODS

We systematically searched Medline, EMBASE, and Web of Science, along with exploring grey literature, to identify longitudinal studies. Data extraction and quality assessment adhered to predetermined criteria, and the results of the included studies were analyzed using a narrative synthesis and graphical display.

RESULTS

We included 52 original studies-40 % were rated as low-risk of bias. Overall, studies showed the low-carbohydrate Mediterranean diet (LCMD), compared to a low-fat diet, was more effective for achieving T2D remission in newly diagnosed patients who also had a weight loss of up to 6 kg. Compared to both the traditional Mediterranean diet and the American Diabetic Association diet, the LCMD was also more effective at diabetes remission for persons with T2D with any duration of diabetes; however, more substantial weight loss of 8 kg was required. Other diets that appeared effective for T2D remission included low-calorie diets and diets high in plant protein sources. Less weight loss was needed to achieve remission on plant-based diets than a low-calorie diet and low-carbohydrate diet.

CONCLUSIONS

Diets high in plant protein sources may support T2D remission, particularly among newly diagnosed patients. For patients with a duration of over 2 years, the combination of plant-based diets with greater weight loss should be considered to induce remission.

Impact of the ketogenic diet as a dietary approach on cardiovascular disease risk factors: a meta-analysis of randomized clinical trials

BACKGROUND

Cardiovascular diseases (CVD) remain the leading cause of mortality globally, and the scarcity of scientific evidence regarding the impact of ketogenic diets on CVD risk factors necessitates urgent attention and redress.

OBJECTIVES

This meta-analysis evaluates the impact of the ketogenic diet on CVD risk factors compared with control diets through randomized controlled trials (RCTs).

METHODS

The study was registered in advance in the PROSPERO database (CRD42023491853). A systematic search was conducted across PubMed, Web of Science, EMBASE, and Cochrane Library to identify relevant RCTs. Fixed and random effects were employed to calculate the mean differences and 95% confidence intervals (CIs) for changes in CVD risk factors pre- and postketogenic diet intervention.

RESULTS

A total of 27 RCTs with 1278 participants were analyzed. The ketogenic diet intervention presented increase in total cholesterol (mean differences: 0.36 mmol/L; 95% CI: 0.15, 0.57; I2: 85.1%), low-density lipoprotein cholesterol (mean differences: 0.35 mmol/L; 95% CI: 0.20, 0.50; I2: 73.9%) and high-density lipoprotein cholesterol (mean differences: 0.16 mmol/L; 95% CI: 0.09, 0.23; I2: 86.7%) concentrations. Reductions were observed in the triglyceride (mean differences: -0.20 mmol/L; 95% CI: -0.29, -0.11; I2: 72.2%), blood glucose (mean differences: -0.18 mmol/L; 95% CI: -0.33, -0.02; I2: 76.4%), blood insulin (mean differences: -8.32 pmol/L; 95% CI: -14.52, -2.12; I2: 81.5%), diastolic blood pressure (mean differences: -1.41 mmHg; 95% CI: -2.57, -0.26; I2: 49.1%), weight (mean differences: -2.59 kg; 95% CI: -3.90, -1.28; I2: 87.4%), and body mass index (mean differences: -1.59 kg/m2; 95% CI: -2.32, -0.86; I2: 84.5%) concentrations after implementing ketogenic diets.

CONCLUSIONS

Although the ketogenic diet demonstrates benefits in terms of triglyceride, blood pressure, weight, and glycemic control, its impact on CVD risk factors, especially the elevated total cholesterol and low-density lipoprotein cholesterol concentrations, warrants a cautious approach.

Nutritional Strategies for the Management of Type 2 Diabetes Mellitus: A Narrative Review

BACKGROUND

Thinking about greater adherence to dietary planning, it is extremely important to be aware of all nutritional strategies and dietary prescriptions available in the literature, and of which of them is the most efficient for the management of T2DM.

METHODS

A search was carried out in 2023 for randomized clinical trials, systematic reviews, meta-analyses, and guidelines in the following databases: Pubmed, Scielo, Web of Science, CrossRef and Google Scholar. In total, 202 articles were collected and analyzed. The period of publications was 1983-2023.

RESULTS

There is still no consensus on what the best nutritional strategy or ideal dietary prescription is, and individuality is necessary. In any case, these references suggest that Mediterranean Diet may of greater interest for the management of T2DM, with the following recommended dietary prescription: 40-50% carbohydrates; 15-25% proteins; 25-35% fats (<7% saturated, 10% polyunsaturated, and 10% monounsaturated); at least 14 g of fiber for every 1000 kcal consumed; and <2300 mg sodium.

CONCLUSIONS

Individuality is the gold standard for dietary prescriptions, however, the Mediterranean diet with low levels of carbohydrates and fats seems to be the most promising strategy for the management of T2DM.

Effect of the Ketogenic Diet on the Prophylaxis and Treatment of Diabetes Mellitus: A Review of the Meta-Analyses and Clinical Trials

The exponentially growing frequency of diagnosing diabetes mellitus means that a verification of the previous dietetic approach to treating the disease seems justified. The simultaneous growth of interest in the ketogenic diet and the development of knowledge in this field have contributed to the increasingly frequent application of the ketogenic diet in diabetes treatment. This paper also deals with that issue; its aim includes an extensive analysis of the influence of the ketogenic diet on the prophylaxis and treatment of diabetes. The paper has been prepared based on a wide, meticulous analysis of the available literature on the subject. Among other findings, a favorable effect of that nutrition model has been demonstrated on the values of glycated hemoglobin, glucose, insulin, or other metabolic parameters in diabetes patients. The effect of the ketogenic diet on the pharmacotherapy of type 1 and type 2 diabetes has been presented and compared with the standard nutritional management plan recommended for that disease. Further research is needed in this field, especially studies with a long follow-up period. The discussed articles report interesting therapeutic advantages to the ketogenic diet in comparison with standard diets.

Effects of Carbohydrate Restriction on Body Weight and Glycemic Control in Individuals with Type 2 Diabetes: A Randomized Controlled Trial of Efficacy in Real-Life Settings

A fully provided, hypocaloric, carbohydrate-reduced high-protein (CRHP) diet compared to a hypocaloric conventional diabetes (CD) diet for 6 weeks improved glycemic control to a greater extent in face of an intended 6% weight loss in individuals with type 2 diabetes mellitus (T2DM). The present 24-week extension of that study reports on the efficacy of CRHP and CD diets in a real-life setting. Sixty-five individuals with T2DM who completed the initial 6-week fully provided diet period (% energy from carbohydrate, protein, and fat was 30/30/40 in CRHP, and 50/17/33 in CD) continued a free-living, dietician guided 24-week period of which 59 individuals completed. The CRHP compared to CD group reported a 4% lower carbohydrate intake and had higher urea excretion by 22% (both p ≤ 0.05) at week 30, suggesting less difference in carbohydrate and protein intake between groups during the 24-week extension compared to week 6. The loss of body weight during the initial 6 weeks was maintained in both groups during the 24-week extension (-5.5 ± 4.5 and -4.6 ± 4.8 kg) as well as HbA_1c (-8.4 ± 6.2 and -8.4 ± 6.9 mmol/mol) with no significant differences between groups. The additional benefits on glucoregulation harnessed by carbohydrate restriction under full diet provision for 6 weeks combined with titrated weight loss could not be maintained in a real-life setting of self-prepared diet aiming on similar diets for 6 months.

Effects of Carbohydrate and Fats in Turkish Patients with Type 2 Diabetes

Aim: This study aimed to assess the effects of different kinds of diet, which were similar in total energy density but different in carbohydrate and fats, on some blood parameters in type 2 diabetics. Materials and Methods: In this study, 33 type 2 diabetics, participants were offered two different kinds of lunches within 7 days intervals. Venous blood samples were collected from the participants half an hour before and after the consumption of these meals (0-180 minutes). Blood parameters such as glucose, insulin, low-density lipoprotein (LDL-C), high-density lipoprotein (HDL-C), and triglyceride were analyzed through blood samples. Results: There was no significance between the values of the change in blood glucose before and after their consumption of the standard meal and etli ekmek. After the consumption of the etli ekmek difference between the participants’ mean insulin level values at 60 and 90 minutes was lower than the standard meal. The values under the curve (AUC) were found to be significant (p

Dose-dependent effect of carbohydrate restriction for type 2 diabetes management: a systematic review and dose-response meta-analysis of randomized controlled trials

BACKGROUND

Carbohydrate restriction is effective for type 2 diabetes management.

OBJECTIVES

We aimed to evaluate the dose-dependent effect of carbohydrate restriction in patients with type 2 diabetes.

METHODS

We systematically searched PubMed, Scopus, and Web of Science to May 2021 for randomized controlled trials evaluating the effect of a carbohydrate-restricted diet (≤45% total calories) in patients with type 2 diabetes. The primary outcome was glycated hemoglobin (HbA1c). Secondary outcomes included fasting plasma glucose (FPG); body weight; serum total, LDL, and HDL cholesterol; triglyceride (TG); and systolic blood pressure (SBP). We performed random-effects dose-response meta-analyses to estimate mean differences (MDs) for a 10% decrease in carbohydrate intake.

RESULTS

Fifty trials with 4291 patients were identified. At 6 months, compared with a carbohydrate intake between 55%-65% and through a maximum reduction down to 10%, each 10% reduction in carbohydrate intake reduced HbA1c (MD, -0.20%; 95% CI, -0.27% to -0.13%), FPG (MD, -0.34 mmol/L; 95% CI, -0.56 to -0.12 mmol/L), and body weight (MD, -1.44 kg; 95% CI, -1.82 to -1.06 kg). There were also reductions in total cholesterol, LDL cholesterol, TG, and SBP. Levels of HbA1c, FPG, body weight, TG, and SBP decreased linearly with the decrease in carbohydrate intake from 65% to 10%. A U-shaped effect was seen for total cholesterol and LDL cholesterol, with the greatest reduction at 40%. At 12 months, a linear reduction was seen for HbA1c and TG. A U-shaped effect was seen for body weight, with the greatest reduction at 35%.

CONCLUSIONS

Carbohydrate restriction can exert a significant and important reduction on levels of cardiometabolic risk factors in patients with type 2 diabetes. Levels of most cardiometabolic outcomes decreased linearly with the decrease in carbohydrate intake. U-shaped effects were seen for total cholesterol and LDL cholesterol at 6 months and for body weight at 12 months.

A prospective study of carbohydrate intake and risk of all-cause and specific-cause mortality

PURPOSE

To investigate the associations between carbohydrate intake and the risk of overall and specific-cause mortality in a prospective cohort study.

METHODS

Diet was measured using 24 h dietary recalls. Underlying cause of death was identified through linkage to the National Death Index. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox proportional hazards regression.

RESULTS

During a median follow-up of 7.1 years among 35,692 participants who aged 20-85 years, a total of 3854 deaths [783 cardiovascular disease (CVD)-specific and 884 cancer-specific death] were identified. Carbohydrate intake was not associated with risk of overall mortality (multivariable-adjusted HR comparing extreme quartiles 1.03, 95% CI 0.94, 1.13, p_trend = 0.799), while higher fiber intake was associated with lower mortality risk (HR 0.86, 95% CI 0.77, 0.95, p_trend = 0.004). Replacing 5% of energy from carbohydrate with both plant fat and plant protein was associated with 13% (95% CI 8%, 17%) and 13% (95% CI 3%, 22%) lower risk of total and CVD mortality, respectively. Whereas a positive or null association was found when replacing carbohydrate with both animal fat and animal protein. Higher carbohydrate-to-fiber ratio was associated with increased risk of overall (HR 1.20, 95% CI 1.09, 1.33, p_trend < 0.001) and cancer-specific (HR 1.17, 95% CI 0.95, 1.44, p_trend = 0.031) mortality.

CONCLUSIONS

Our findings suggested that high fiber diet or diet with low carbohydrate-to-fiber ratio was associated with lower long-term death risk, and provided evidence for the health benefit from dietary substitution of both plant fat and plant protein for carbohydrate.

Effects of Diet, Lifestyle, Chrononutrition and Alternative Dietary Interventions on Postprandial Glycemia and Insulin Resistance

As years progress, we are found more often in a postprandial than a postabsorptive state. Chrononutrition is an integral part of metabolism, pancreatic function, and hormone secretion. Eating most calories and carbohydrates at lunch time and early afternoon, avoiding late evening dinner, and keeping consistent number of daily meals and relative times of eating occasions seem to play a pivotal role for postprandial glycemia and insulin sensitivity. Sequence of meals and nutrients also play a significant role, as foods of low density such as vegetables, salads, or soups consumed first, followed by protein and then by starchy foods lead to ameliorated glycemic and insulin responses. There are several dietary schemes available, such as intermittent fasting regimes, which may improve glycemic and insulin responses. Weight loss is important for the treatment of insulin resistance, and it can be achieved by many approaches, such as low-fat, low-carbohydrate, Mediterranean-style diets, etc. Lifestyle interventions with small weight loss (7-10%), 150 min of weekly moderate intensity exercise and behavioral therapy approach can be highly effective in preventing and treating type 2 diabetes. Similarly, decreasing carbohydrates in meals also improves significantly glycemic and insulin responses, but the extent of this reduction should be individualized, patient-centered, and monitored. Alternative foods or ingredients, such as vinegar, yogurt, whey protein, peanuts and tree nuts should also be considered in ameliorating postprandial hyperglycemia and insulin resistance. This review aims to describe the available evidence about the effects of diet, chrononutrition, alternative dietary interventions and exercise on postprandial glycemia and insulin resistance.

Effects of consumption of coconut oil or coconut on glycemic control and insulin sensitivity: A systematic review and meta-analysis of interventional trials

BACKGROUND AND AIMS

The often purported claim that coconut fat is beneficial for cardiovascular health and was disputed in several recent meta-analyses. However, the evidence on the effects of coconut fat intake on glycemic control remains equivocal. We conducted a systematic review and meta-analysis in accordance with the PRISMA guidelines to determine the effects of dietary coconut fats on markers of acute and long-term glycemic control.

METHODS AND RESULTS

PubMed, Scopus, ProQuest, and Web-of-Science databases were searched and the records were screened by three independent reviewers to identify interventional studies examining acute and long-term (i.e., >10 days) effects of coconut fat on glycemic control. DerSimonian-Laird random-effects meta-analyses were performed using the meta-package in R (4.0.2). Seven interventional studies on acute effects and 11 interventional studies on long-term effects of coconut fat were included. Meals with coconut fat acutely increased the incremental area under the curve (AUC) of glucose (p = 0.046) and decreased the incremental AUC of insulin (p = 0.037) vs. control meals. Long-term coconut fat intake increased HOMA-IR (p = 0.049), but did not significantly affect fasting glucose, insulin, or HOMA-β vs. control meals.

CONCLUSIONS

Coconut fat in meals seems to be associated with a diminished postprandial insulin response, resulting in a subtle increase in the postprandial glycemic response. Long-term intake of coconut fat seems to increase insulin resistance, yet does not seem to be beneficial for long-term glycemic control. Thus, our results disprove the popular claim that coconut fat improves glycemic control.

REGISTRATION

PROSPERO registry (CRD42020183450).

Dietary Intake and TCF7L2 rs7903146 T Allele Are Associated with Elevated Blood Glucose Levels in Healthy Individuals

INTRODUCTION

Type 2 diabetes (T2D) is a leading cause of global mortality with diet and genetics being considered amongst the most significant risk factors. Recently, studies have identified a single polymorphism of the TCF7L2 gene (rs7903146) as the most important genetic contributor. However, no studies have explored this factor in a healthy population and using glycated haemoglobin (HbA1c), which is a reliable long-term indicator of glucose management. This study investigates the association of the genetic polymorphism rs7903146 and dietary intake with T2D risk in a population free of metabolic disease.

METHODS

T2D risk was assessed using HbA1c plasma concentrations and dietary intake via a validated Food Frequency Questionnaire in 70 healthy participants.

RESULTS

T allele carriers had higher HbA1c levels than the CC group (32.4 ± 7.2 mmol/mol vs. 30.3 ± 7.6 mmol/mol, p = 0.005). Multiple regression reported associations between diet, genotype and HbA1c levels accounting for 37.1% of the variance in HbA1c (adj. R2 = 0.371, p < 0.001). The following macronutrients, expressed as a median percentage of total energy intake (TEI) in the risk group, were positively associated with HbA1c concentration: carbohydrate (≥39% TEI, p < 0.005; 95% CI 0.030/0.130) protein (≥21% TEI, p < 0.005, 95% CI 0.034/0.141), monounsaturated (≥15% TEI p < 0.05, 95% CI 0.006/0.163) and saturated fatty acids (≥13% TEI; p < 0.05, 95% CI 0.036/0.188).

CONCLUSION

Carriers of the T allele showed significantly higher levels of HbA1c compared to non-carriers. Dietary intake affected T2D risk to a greater extent than genetic effects of TCF7L2rs7903146 genotype in a healthy population. The study focus on healthy individuals is beneficial due to the applicability of findings for T2D screening.

Low Carbohydrate Dietary Approaches for People With Type 2 Diabetes-A Narrative Review

Although carbohydrate restriction is not a new approach for the management of Type 2 diabetes, interest in its safety and efficacy has increased significantly in recent years. The purpose of the current narrative review is to summarise the key relevant research and practical considerations in this area, as well as to explore some of the common concerns expressed in relation to the use of such approaches. There is a strong physiological rationale supporting the role of carbohydrate restriction for the management of Type 2 diabetes, and available evidence suggests that low carbohydrate dietary approaches (LCDs) are as effective as, or superior to, other dietary approaches for its management. Importantly, LCDs appear to be more effective than other dietary approaches for facilitating a reduction in the requirement for certain medications, which leads to their effects on other health markers being underestimated. LCDs have also been demonstrated to be an effective method for achieving remission of Type 2 diabetes for some people. The available evidence does not support concerns that LCDs increase the risk of cardiovascular disease, that such approaches increase the risk of nutrient deficiencies, or that they are more difficult to adhere to than other dietary approaches. A growing number of organisations support the use of LCDs as a suitable choice for individuals with Type 2 diabetes.

Body weight and metabolic risk factors in patients with type 2 diabetes on a self-selected high-protein low-carbohydrate diet

PURPOSE

We previously reported beneficial glucoregulatory effects of a fully provided carbohydrate-reduced, high-protein (CRHP) diet in patients with type 2 diabetes mellitus (T2DM) in a crossover 2 × 6-week trial, in which patients maintained their body weight. Here, we investigated physiological changes during an additional 6-month period on a self-selected and self-prepared CRHP diet.

METHODS

Twenty-eight patients with T2DM were instructed to consume a CRHP diet (30% of energy from carbohydrate and 30% from protein) for 24 weeks, after an initial 2 × 6-week trial when all food was prepared and provided to them. Patients received dietary advice every 2 weeks. At weeks 0, 6, 12 and 36, they underwent a 3-h intravenous glucose tolerance test, a 4-h mixed meal test, and a 48-h continuous glucose monitoring. Liver, muscle, pancreas, and visceral fat contents were measured by magnetic resonance imaging.

RESULTS

During the 24-week self-selected diet period (weeks 12-36), body weight, visceral fat, liver fat, and glycated haemoglobin were maintained at the same levels achieved at the end of the fully provided diet period, and were still lower than at baseline (P < 0.05). Postprandial insulinaemia and insulin secretion were significantly greater (P < 0.05). At week 36, fasting insulin and C-peptide levels increased (P < 0.01) and daily glycaemia decreased further (P < 0.05) when compared with the end of the fully provided diet period.

CONCLUSION

Substituting dietary carbohydrate for protein and fat has metabolic benefits in patients with T2DM. These beneficial effects are maintained or augmented over the next 6 months when patients self-select and self-prepare this diet in a dietitian-supported setting.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02764021.

Effects of a Self-Prepared Carbohydrate-Reduced High-Protein Diet on Cardiovascular Disease Risk Markers in Patients with Type 2 Diabetes

We previously observed beneficial effects of a carbohydrate-reduced, high-protein (CRHP) diet on cardiovascular risk markers in patients with type 2 diabetes mellitus (T2DM) in a crossover 2 × 6-week trial, when all food was provided to subjects as ready-to-eat meals. Here, we report the results from a 6-month open label extension: 28 patients with T2DM were instructed to self-prepare the CRHP diet with dietetic guidance. At weeks 0, 6, 12, and 36, fasting and postprandial (4-h meal test) blood samples were collected for measurements of total, high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol, triacylglycerol (TG), apolipoproteins A1 and B, non-esterified fatty acids (NEFA), C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), and interleukin-6. Diurnal blood pressure and heart rate were also assessed. At the end of the study (week 36), concentrations of fasting total and LDL-cholesterol, fasting and postprandial NEFA and TG, and fasting apolipoprotein-B, CRP and TNF-α concentrations were significantly lower compared with week 0 (p < 0.05). A significant decrease in diurnal heart rate was also observed. From week 12 to 36, an increase in HDL-cholesterol and apolipoprotein-A1 concentrations and a further reduction in fasting and postprandial NEFA (p < 0.05) were found. These changes were independent of minor fluctuations in body weight. We conclude that the substitution of dietary carbohydrate for protein and fat has beneficial effects on several cardiovascular risk markers in patients with T2DM, which are maintained or augmented over the next 6 months when patients select and prepare the CRHP diet on their own in a dietitian-supported setting.

Identifying sustainable lifestyle strategies for maintaining good glycemic control: a validation of qualitative findings

INTRODUCTION

Diabetes self-care practices are less effective outside of controlled research settings, and almost half of patients do not achieve good glycemic control. Qualitative studies suggest some lifestyle strategies may be linked to good control, but those strategies have not been validated. This study provides population-based evidence that dietary strategies identified in qualitative studies are associated with glycemic control in US patients with diabetes.

RESEARCH DESIGN AND METHODS

In a cross-sectional sample of the National Health and Nutrition Examination Survey (NHANES), qualitative self-management themes were matched to survey questions and used to predict good glycemic control (hemoglobin A1c <7.0% (53 mmol/mol)). Patients were limited to those 50 years of age and older with a diagnosis of diabetes for at least 1 year (N=465).

RESULTS

Patients averaged 65 years of age with a body mass index of 32.56 kg/m2 and 42% reported no physical activity. In logistic regression models controlling for sociodemographic and medical history variables, self-monitoring of blood glucose, weight loss, and physical activity were not significantly associated with glycemic control. Instead, dietary practices such as consuming low-calorie foods (OR=4.05, 95% CI 1.64 to 10.01), eating less fat (OR=2.15, 95% CI 1.03 to 4.47), and reducing sodium (OR=1.94, 95% CI 1.18 to 3.17) were significantly associated with good glycemic control, as was diabetes education or consultation with a dietitian (OR=3.48, 95% CI 1.28 to 9.45). Non-adherence to medications (OR=0.27, 95% CI 0.11 to 0.68) and general dietary descriptions, such as following a 'diabetic diet' (OR=0.32, 95% CI 0.17 to 0.57) and 'changing eating habits for weight loss' (OR=0.34, 95% CI 0.15 to 0.77), were associated with poorer glycemic control.

CONCLUSIONS

The NHANES validation of lifestyle management strategies suggests practices that may be sustainable. In a population that tends to be obese with low physical activity, successful self-care might emphasize specific dietary practices offering concrete touchpoints for patient communication and guidance. These strategies might help maintain glycemic control.

Fat, Sugar or Gut Microbiota in Reducing Cardiometabolic Risk: Does Diet Type Really Matter?

The incidence of cardiometabolic diseases, such as obesity, diabetes, and cardiovascular diseases, is constantly rising. Successful lifestyle changes may limit their incidence, which is why researchers focus on the role of nutrition in this context. The outcomes of studies carried out in past decades have influenced dietary guidelines, which primarily recommend reducing saturated fat as a therapeutic approach for cardiovascular disease prevention, while limiting the role of sugar due to its harmful effects. On the other hand, a low-carbohydrate diet (LCD) as a method of treatment remains controversial. A number of studies on the effect of LCDs on patients with type 2 diabetes mellitus proved that it is a safe and effective method of dietary management. As for the risk of cardiovascular diseases, the source of carbohydrates and fats corresponds with the mortality rate and protective effect of plant-derived components. Additionally, some recent studies have focused on the gut microbiota in relation to cardiometabolic diseases and diet as one of the leading factors affecting microbiota composition. Unfortunately, there is still no precise answer to the question of which a single nutrient plays the most important role in reducing cardiometabolic risk, and this review article presents the current state of the knowledge in this field.

Association between the proportions of carbohydrate and fat intake and hypertension risk: findings from the China Health and Nutrition Survey

OBJECTIVE

The aim of this study was to expound the dietary effects of different proportions of carbohydrate and fat on hypertension in the Chinese population.

METHODS

We used data derived from the China Health and Nutrition Survey (CHNS) from 1991 to 2011. In total, 10 459 Chinese participants aged over 12 years were included in the final analysis. A multivariable Cox regression was used to calculate the hazard ratio and 95% confidence interval (95% CI) of hypertension in each group, and the medium proportion of carbohydrate and fat (MPCF) diet intake group was used as the reference.

RESULTS

Compared with the participants who consumed an MPCF diet, the individuals who consumed a high-carbohydrate and low-fat (HCLF) diet had a higher risk of developing hypertension (hazard ratio: 1.295, 95% CI: 1.167-1.436), especially the individuals who were young (hazard ratio: 1.422, 95% CI: 1.106-1.828), were living in rural areas (hazard ratio: 1.373, 95% CI: 1.206-1.565) and consumed alcohol (hazard ratio: 1.363, 95% CI: 1.153-1.611). In addition, a low-carbohydrate and high-fat (LCHF) diet was not associated with hypertension (hazard ratio: 0.861, 95% CI: 0.694-1.068). Moreover, these associations were observed at the majority energy intake level.

CONCLUSION

An HCLF diet was significantly associated with an increased risk of hypertension.

Current Evidence Regarding Low-carb Diets for The Metabolic Control of Type-2 Diabetes

The management of diabetes requires a medical nutrition therapy as an essential part of this treatment. There should be no "one-size-fits-all" eating pattern for different patient´s profiles with diabetes. It is clinically complex to suggest an ideal percentage of calories from carbohydrates, protein and lipids recommended for all patients with diabetes. Among the eating patterns that have shown beneficial effects on metabolic control of patients with type 2 diabetes is the lowcarb diet, since the carbohydrate ingestion is viewed as the most important determinant of postprandial glucose and insulin response. In this context, theoretically, it could make sense to reduce the daily amount of carbohydrates ingested, to achieve lower levels of HbA1c. There could be risks associated to this approach. The adherence to a low-carb diet is here also discussed. This narrative review shows on the current evidence for answering these questions regarding low-carb diet as a possible alternative eating pattern for type 2 diabetes.

Diet and exercise in the prevention and treatment of type 2 diabetes mellitus

Evidence from observational studies and randomized trials suggests that prediabetes and type 2 diabetes mellitus (T2DM) can develop in genetically susceptible individuals in parallel with weight (that is, fat) gain. Accordingly, studies show that weight loss can produce remission of T2DM in a dose-dependent manner. A weight loss of ~15 kg, achieved by calorie restriction as part of an intensive management programme, can lead to remission of T2DM in ~80% of patients with obesity and T2DM. However, long-term weight loss maintenance is challenging. Obesity and T2DM are associated with diminished glucose uptake in the brain that impairs the satiating effect of dietary carbohydrate; therefore, carbohydrate restriction might help maintain weight loss and maximize metabolic benefits. Likewise, increases in physical activity and fitness are an important contributor to T2DM remission when combined with calorie restriction and weight loss. Preliminary studies suggest that a precision dietary management approach that uses pretreatment glycaemic status to stratify patients can help optimize dietary recommendations with respect to carbohydrate, fat and dietary fibre. This approach might lead to improved weight loss maintenance and glycaemic control. Future research should focus on better understanding the individual response to dietary treatment and translating these findings into clinical practice.

Application of n-of-1 Clinical Trials in Personalized Nutrition Research: A Trial Protocol for Westlake N-of-1 Trials for Macronutrient Intake (WE-MACNUTR)

Personalized dietary recommendations can help with more effective disease prevention. This study aims to investigate the individual postprandial glucose response to diets with diverse macronutrient proportions at both the individual level and population level, and explore the potential of the novel single-patient (n-of-1) trial for personalization of diet. Secondary outcomes include individual phenotypic responses and the effects of dietary ingredients on the composition of gut microbiota. Westlake N-of-1 Trials for Macronutrient Intake is a multiple crossover feeding trial consisting of 3 successive 12-d dietary intervention pairs including a 6-d washout period before each 6-d isocaloric dietary intervention: a 6-d high-fat, low-carbohydrate diet, and a 6-d low-fat, high-carbohydrate diet. The results will help provide personalized dietary recommendations for macronutrients in terms of postprandial blood glucose responses. The proposed n-of-1 trial methods could help in optimizing individual health and advancing health care. This trial was registered with clinicaltrials.gov (NCT04125602).

Reduction in saturated fat intake for cardiovascular disease

BACKGROUND

Reducing saturated fat reduces serum cholesterol, but effects on other intermediate outcomes may be less clear. Additionally, it is unclear whether the energy from saturated fats eliminated from the diet are more helpfully replaced by polyunsaturated fats, monounsaturated fats, carbohydrate or protein.

OBJECTIVES

To assess the effect of reducing saturated fat intake and replacing it with carbohydrate (CHO), polyunsaturated (PUFA), monounsaturated fat (MUFA) and/or protein on mortality and cardiovascular morbidity, using all available randomised clinical trials.

SEARCH METHODS

We updated our searches of the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (Ovid) and Embase (Ovid) on 15 October 2019, and searched Clinicaltrials.gov and WHO International Clinical Trials Registry Platform (ICTRP) on 17 October 2019.

SELECTION CRITERIA

Included trials fulfilled the following criteria: 1) randomised; 2) intention to reduce saturated fat intake OR intention to alter dietary fats and achieving a reduction in saturated fat; 3) compared with higher saturated fat intake or usual diet; 4) not multifactorial; 5) in adult humans with or without cardiovascular disease (but not acutely ill, pregnant or breastfeeding); 6) intervention duration at least 24 months; 7) mortality or cardiovascular morbidity data available.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed inclusion, extracted study data and assessed risk of bias. We performed random-effects meta-analyses, meta-regression, subgrouping, sensitivity analyses, funnel plots and GRADE assessment.

MAIN RESULTS

We included 15 randomised controlled trials (RCTs) (16 comparisons, 56,675 participants), that used a variety of interventions from providing all food to advice on reducing saturated fat. The included long-term trials suggested that reducing dietary saturated fat reduced the risk of combined cardiovascular events by 17% (risk ratio (RR) 0.83; 95% confidence interval (CI) 0.70 to 0.98, 12 trials, 53,758 participants of whom 8% had a cardiovascular event, I² = 67%, GRADE moderate-quality evidence). Meta-regression suggested that greater reductions in saturated fat (reflected in greater reductions in serum cholesterol) resulted in greater reductions in risk of CVD events, explaining most heterogeneity between trials. The number needed to treat for an additional beneficial outcome (NNTB) was 56 in primary prevention trials, so 56 people need to reduce their saturated fat intake for ~four years for one person to avoid experiencing a CVD event. In secondary prevention trials, the NNTB was 53. Subgrouping did not suggest significant differences between replacement of saturated fat calories with polyunsaturated fat or carbohydrate, and data on replacement with monounsaturated fat and protein was very limited. We found little or no effect of reducing saturated fat on all-cause mortality (RR 0.96; 95% CI 0.90 to 1.03; 11 trials, 55,858 participants) or cardiovascular mortality (RR 0.95; 95% CI 0.80 to 1.12, 10 trials, 53,421 participants), both with GRADE moderate-quality evidence. There was little or no effect of reducing saturated fats on non-fatal myocardial infarction (RR 0.97, 95% CI 0.87 to 1.07) or CHD mortality (RR 0.97, 95% CI 0.82 to 1.16, both low-quality evidence), but effects on total (fatal or non-fatal) myocardial infarction, stroke and CHD events (fatal or non-fatal) were all unclear as the evidence was of very low quality. There was little or no effect on cancer mortality, cancer diagnoses, diabetes diagnosis, HDL cholesterol, serum triglycerides or blood pressure, and small reductions in weight, serum total cholesterol, LDL cholesterol and BMI. There was no evidence of harmful effects of reducing saturated fat intakes.

AUTHORS' CONCLUSIONS

The findings of this updated review suggest that reducing saturated fat intake for at least two years causes a potentially important reduction in combined cardiovascular events. Replacing the energy from saturated fat with polyunsaturated fat or carbohydrate appear to be useful strategies, while effects of replacement with monounsaturated fat are unclear. The reduction in combined cardiovascular events resulting from reducing saturated fat did not alter by study duration, sex or baseline level of cardiovascular risk, but greater reduction in saturated fat caused greater reductions in cardiovascular events.

Does high dietary protein intake contribute to the increased risk of developing prediabetes and type 2 diabetes?

Insulin resistance is a complex metabolic disorder implicated in the development of many chronic diseases. While it is generally accepted that body mass loss should be the primary approach for the management of insulin resistance-related disorders in overweight and obese individuals, there is no consensus among researchers regarding optimal protein intake during dietary restriction. Recently, it has been suggested that increased plasma branched-chain amino acids concentrations are associated with the development of insulin resistance and type 2 diabetes. The exact mechanism by which excessive amino acid availability may contribute to insulin resistance has not been fully investigated. However, it has been hypothesised that mammalian target of rapamycin (mTOR) complex 1 hyperactivation in the presence of amino acid overload contributes to reduced insulin-stimulated glucose uptake because of insulin receptor substrate (IRS) degradation and reduced Akt-AS160 activity. In addition, the long-term effects of high-protein diets on insulin sensitivity during both weight-stable and weight-loss conditions require more research. This review focusses on the effects of high-protein diets on insulin sensitivity and discusses the potential mechanisms by which dietary amino acids can affect insulin signalling. Novelty: Excess amino acids may over-activate mTOR, resulting in desensitisation of IRS-1 and reduced insulin-mediated glucose uptake.

Therapeutic use of intermittent fasting and ketogenic diet as an alternative treatment for type 2 diabetes in a normal weight woman: a 14-month case study

This case demonstrates the effective and sustainable use of intermittent fasting (IF) and ketogenic diet (KD) in a normal weight patient with type 2 diabetes, who did not attain glycaemic control with a standard care approach. A 57-year-old woman with type 2 diabetes treated with metformin and strict adherence to a standard diabetic diet presented with a haemoglobin A1c (HbA1c) of 9.3%. Within 4 months of transitioning to KD, combined with IF, she achieved glycaemic control off pharmacotherapy, with HbA1c of 6.4. IF regimens started as 24 hours three times per week, followed by 42 hours three times per week, then 42 hours two times per week and 16 hours once per week. A maintenance phase was then begun at 8 months; IF was reduced to 16 hours per day, with 24 hours three times per month, and metformin was restarted. At 14 months, HbA1c reached 5.8%, and body mass index was minimally changed.

Reduction in saturated fat intake for cardiovascular disease

BACKGROUND

Reducing saturated fat reduces serum cholesterol, but effects on other intermediate outcomes may be less clear. Additionally, it is unclear whether the energy from saturated fats eliminated from the diet are more helpfully replaced by polyunsaturated fats, monounsaturated fats, carbohydrate or protein.

OBJECTIVES

To assess the effect of reducing saturated fat intake and replacing it with carbohydrate (CHO), polyunsaturated (PUFA), monounsaturated fat (MUFA) and/or protein on mortality and cardiovascular morbidity, using all available randomised clinical trials.

SEARCH METHODS

We updated our searches of the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (Ovid) and Embase (Ovid) on 15 October 2019, and searched Clinicaltrials.gov and WHO International Clinical Trials Registry Platform (ICTRP) on 17 October 2019.

SELECTION CRITERIA

Included trials fulfilled the following criteria: 1) randomised; 2) intention to reduce saturated fat intake OR intention to alter dietary fats and achieving a reduction in saturated fat; 3) compared with higher saturated fat intake or usual diet; 4) not multifactorial; 5) in adult humans with or without cardiovascular disease (but not acutely ill, pregnant or breastfeeding); 6) intervention duration at least 24 months; 7) mortality or cardiovascular morbidity data available.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed inclusion, extracted study data and assessed risk of bias. We performed random-effects meta-analyses, meta-regression, subgrouping, sensitivity analyses, funnel plots and GRADE assessment.

MAIN RESULTS

We included 15 randomised controlled trials (RCTs) (16 comparisons, ~59,000 participants), that used a variety of interventions from providing all food to advice on reducing saturated fat. The included long-term trials suggested that reducing dietary saturated fat reduced the risk of combined cardiovascular events by 21% (risk ratio (RR) 0.79; 95% confidence interval (CI) 0.66 to 0.93, 11 trials, 53,300 participants of whom 8% had a cardiovascular event, I² = 65%, GRADE moderate-quality evidence). Meta-regression suggested that greater reductions in saturated fat (reflected in greater reductions in serum cholesterol) resulted in greater reductions in risk of CVD events, explaining most heterogeneity between trials. The number needed to treat for an additional beneficial outcome (NNTB) was 56 in primary prevention trials, so 56 people need to reduce their saturated fat intake for ~four years for one person to avoid experiencing a CVD event. In secondary prevention trials, the NNTB was 32. Subgrouping did not suggest significant differences between replacement of saturated fat calories with polyunsaturated fat or carbohydrate, and data on replacement with monounsaturated fat and protein was very limited. We found little or no effect of reducing saturated fat on all-cause mortality (RR 0.96; 95% CI 0.90 to 1.03; 11 trials, 55,858 participants) or cardiovascular mortality (RR 0.95; 95% CI 0.80 to 1.12, 10 trials, 53,421 participants), both with GRADE moderate-quality evidence. There was little or no effect of reducing saturated fats on non-fatal myocardial infarction (RR 0.97, 95% CI 0.87 to 1.07) or CHD mortality (RR 0.97, 95% CI 0.82 to 1.16, both low-quality evidence), but effects on total (fatal or non-fatal) myocardial infarction, stroke and CHD events (fatal or non-fatal) were all unclear as the evidence was of very low quality. There was little or no effect on cancer mortality, cancer diagnoses, diabetes diagnosis, HDL cholesterol, serum triglycerides or blood pressure, and small reductions in weight, serum total cholesterol, LDL cholesterol and BMI. There was no evidence of harmful effects of reducing saturated fat intakes.

AUTHORS' CONCLUSIONS

The findings of this updated review suggest that reducing saturated fat intake for at least two years causes a potentially important reduction in combined cardiovascular events. Replacing the energy from saturated fat with polyunsaturated fat or carbohydrate appear to be useful strategies, while effects of replacement with monounsaturated fat are unclear. The reduction in combined cardiovascular events resulting from reducing saturated fat did not alter by study duration, sex or baseline level of cardiovascular risk, but greater reduction in saturated fat caused greater reductions in cardiovascular events.

Dietary fats and cardiometabolic disease: mechanisms and effects on risk factors and outcomes

The effect of dietary fats on cardiometabolic diseases, including cardiovascular diseases and type 2 diabetes mellitus, has generated tremendous interest. Many earlier investigations focused on total fat and conventional fat classes (such as saturated and unsaturated fats) and their influence on a limited number of risk factors. However, dietary fats comprise heterogeneous molecules with diverse structures, and growing research in the past two decades supports correspondingly complex health effects of individual dietary fats. Moreover, health effects of dietary fats might be modified by additional factors, such as accompanying nutrients and food-processing methods, emphasizing the importance of the food sources. Accordingly, the rapidly increasing scientific findings on dietary fats and cardiometabolic diseases have generated debate among scientists, caused confusion for the general public and present challenges for translation into dietary advice and policies. This Review summarizes the evidence on the effects of different dietary fats and their food sources on cell function and on risk factors and clinical events of cardiometabolic diseases. The aim is not to provide an exhaustive review but rather to focus on the most important evidence from randomized controlled trials and prospective cohort studies and to highlight current areas of controversy and the most relevant future research directions for understanding how to improve the prevention and management of cardiometabolic diseases through optimization of dietary fat intake.

Optimal Dietary Strategies for Prevention of Atherosclerotic Cardiovascular Disease in Diabetes: Evidence and Recommendations

PURPOSE OF REVIEW

This review presents the current available evidence of the effects of several dietary patterns on atherosclerotic cardiovascular disease (ASCVD) risk in patients with type 2 diabetes (T2D).

RECENT FINDINGS

Evidence demonstrates improvements in cardiovascular risk factors with some dietary patterns in the general population. However, evidence is limited for glycemic control and cardiovascular benefit in patients with T2D for Dietary Approaches to Stop Hypertension and plant-based dietary patterns. Evidence suggests that carbohydrate-restricted dietary patterns improve glycemic control and decrease the use of anti-hyperglycemic medications. The Mediterranean dietary pattern has the most evidence for glycemic control and decreased ASCVD risk in patients with T2D. There is no evidence on ASCVD outcomes in patients with T2D for any other dietary pattern. The Mediterranean dietary pattern has the most evidence for cardiovascular benefit in patients with T2D. Future research should examine the effect of dietary patterns on ASCVD outcomes.

Perspective: Network Meta-analysis Reaches Nutrition Research: Current Status, Scientific Concepts, and Future Directions

Traditional pairwise meta-analysis (PMA) is a very useful method that pools evidence from one study design type if appropriate; its widespread use in nutrition research is an important phenomenon. Recently, a promising method for more advanced evidence-synthesis, called network meta-analysis (NMA), was introduced. NMA is an extension of PMA that enables simultaneous comparison of multiple interventions. NMA combines direct evidence (i.e., trials comparing 2 interventions directly) and indirect evidence (i.e., from a connected route via ≥1 comparators, e.g. placebo) in a network of studies. NMAs have the potential to advance knowledge in the field of nutrition as they provide insights that cannot be obtained by individual 2-arm randomized controlled trials or PMA. Thus, in this perspective paper, we aim to summarize the current (methodologic) status of published NMAs in nutrition research and emphasize advances and strengths in comparison with traditional PMA through specific examples, and highlight potential pitfalls and limitations. NMA is an emerging methodology in the field of nutrition research. A PubMed search identified only 23 nutrition research-related NMAs published since the inception of journals up to January 8, 2019 (61% of them published since 2017), compared with >5000 published PMAs. Moreover, we aim to highlight the scientific concepts and standards through the use of the following NMA example: "Which type of oils/solid fats offers the greatest impact on blood lipids?" In this regard, we discuss intervention definitions, transitivity/similarity, statistical methods, description and visualization of results, inconsistency, ranking, dissemination bias, assessing the certainty of evidence by Grading of Recommendations Assessment, Development and Evaluation, and reporting guidelines. We expect that rigorously conducted NMAs based on high-quality systematic reviews will become the new evidence synthesis benchmark in nutrition research. However, caution is warranted because abuse and misinterpretations of PMA and NMA findings could hamper the scientific field and possibly decision-making regarding public policy.

Impact of different dietary approaches on blood lipid control in patients with type 2 diabetes mellitus: a systematic review and network meta-analysis

The aim of this study was to assess the effects of different dietary approaches on low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and triglyceride (TG) levels in patients with type 2 diabetes (T2D) by applying network meta-analysis (NMA). Systematic electronic and hand searches were conducted until January 2018. Randomized controlled trials (RCTs) with an intervention period of ≥ 12 weeks, focussing on adults with T2D, and comparing dietary approaches regarding LDL, HDL or TGs, were included. For each outcome measure, random effects NMA was performed in order to determine the effect of each dietary approach compared to every other dietary intervention. Mean differences (MDs) and 95% confidence intervals (95% CIs) were calculated, and for the ranking, the surface under the cumulative ranking curves (SUCRA) was determined. Additionally, the credibility of evidence was evaluated. 52 RCTs (44 for LDL, 48 for HDL and 52 for TGs) comparing nine dietary approaches (low fat, vegetarian, Mediterranean, high protein, moderate carbohydrate, low carbohydrate, control, low glycaemic index/glycaemic load and Palaeolithic diet) enrolling 5360 T2D patients were included. The vegetarian diet most effectively reduced LDL levels [MD (95% CI): - 0.33 (- 0.55, - 0.12) mmol/L; compared to the control diet]. The Mediterranean diet beneficially raised HDL [MD (95% CI): 0.09 (0.04, 0.15) mmol/L] and decreased TG levels [MD (95% CI): - 0.41 (- 0.72, - 0.10) mmol/L] compared to the control diet. The Mediterranean diet was the most effective dietary approach to manage diabetic dyslipidaemia altogether (SUCRA: 79%). The overall findings are mainly limited by low credibility of evidence.

Salivary α-amylase copy number is not associated with weight trajectories and glycemic improvements following clinical weight loss: results from a 2-phase dietary intervention study

BACKGROUND

Several studies recently reported contradicting results regarding the link between amylase 1 (AMY1) copy numbers (CNs), obesity, and type 2 diabetes.

OBJECTIVE

The aim of this study was to assess the impact of AMY1 CN on anthropometrics and glycemic outcomes in obese individuals following a 2-phase dietary weight loss intervention.

METHODS

Using the paralog ratio test, AMY1 CNs were accurately measured in 761 obese individuals from the DiOGenes study. Subjects first underwent an 8-wk low-calorie diet (LCD, at 800 kcal/d) and then were randomly assigned to a 6-mo weight maintenance dietary (WMD) intervention with arms having different glycemic loads.

RESULTS

At baseline, a modest association between AMY1 CN and BMI (P = 0.04) was observed. AMY1 CN was not associated with baseline glycemic variables. In addition, AMY1 CN was not associated with anthropometric or glycemic outcomes following either LCD or WMD. Interaction analyses between AMY1 CN and nutrient intake did not reveal any significant association with clinical parameters (at baseline and following LCD or WMD) or when testing gene × WMD interactions during the WMD phase.

CONCLUSION

In the absence of association with weight trajectories or glycemic improvements, the AMY1 CN cannot be considered as an important biomarker for response to a clinical weight loss and weight maintenance programs in overweight/obese subjects. This trial was registered at www.clinicaltrials.gov as NCT00390637.

Inadequate fat or carbohydrate intake was associated with an increased incidence of type 2 diabetes mellitus in Korean adults: A 12-year community-based prospective cohort study

AIMS

Few studies have focused on the relationship between long-term fat intake and type 2 diabetes mellitus (T2D) risk in Asia where fat intake is relatively lower than the Western countries. We examined association of dietary fat and carbohydrate intake with incidence of T2D among Korean adults.

METHODS

Based on the data from the Korean Genome and Epidemiology Study, a total of 5595 adults aged 40-69 years without diabetes, cardiovascular diseases or any cancer at baseline were included. Dietary intake was measured by the validated semi-quantitative food frequency questionnaire. Cox proportional hazards regression analysis was used to calculate multivariable-adjusted relative risks (RRs) and 95% confidence intervals (CIs).

RESULTS

During a median follow-up of 138-months, 1010 cases of T2D were newly determined. The proportion of participants with fat intake less than 15% of total energy and with carbohydrate intake more than 65% of total energy was 59.0% and 88.9%, respectively. After adjusting for confounders, a very-low-fat intake was associated with an increased risk of T2D (RR of Quartile 1 vs Quartile 4, 1.74; 95% CI, 1.18-2.57; p for trend = 0.0058) in women. A very-high-carbohydrate intake was associated with an increased risk of T2D in men (RR of Quartile 4 vs Quartile 1, 1.54; 95% CI, 1.03-2.30; p for trend = 0.0124) and women (RR of Quartile 4 vs Quartile 1, 1.69; 95% CI, 1.08-2.67; p for trend = 0.0376).

CONCLUSIONS

A very-low-fat or very-high-carbohydrate intake may increase the T2D risk and might be associated with lower intake of various nutrients and unbalanced macronutrient composition.

Fat Versus Carbohydrate-Based Energy-Restricted Diets for Weight Loss in Patients With Type 2 Diabetes

PURPOSE OF REVIEW

The prevalence of combined obesity and diabetes has increased dramatically in the last few decades. Although medical and surgical weight management are variably effective in addressing this epidemic, it is essential to parallel these strategies with a hypocaloric diet comprising the appropriate macronutrient composition to induce weight loss, enhance glycemic control, and improve cardiovascular risk factors. This review reports the current evidence of the role of carbohydrates and fat-based diets for weight management in patients with combined type 2 diabetes (T2D) and obesity.

RECENT FINDINGS

Low-carbohydrate diets were shown to decrease postprandial glucose levels whereas high-carbohydrate, low-fat diets are considered cardio-protective. A diet with an optimal macronutrient composition remains uncertain for patients with combined T2D and obesity. Further research is still needed to define the best dietary composition that achieves the maximum benefits on weight management, glycemic control, and cardiovascular risk factors.

Effects of low-carbohydrate- compared with low-fat-diet interventions on metabolic control in people with type 2 diabetes: a systematic review including GRADE assessments

Background

It remains uncertain which diet is best for people with type 2 diabetes (T2D).

Objective

We compared the effects of dietary carbohydrate restriction with fat restriction on markers of metabolic syndrome and quality of life in people with T2D.

Design

This systematic review of randomized controlled trials (RCTs) and controlled clinical trials (CCTs) compares the effects of a low-carbohydrate [≤40% of energy (%)] diet with those of a low-fat (≤30%) diet over a period of ≥4 wk in patients with T2D. Two investigators independently selected studies, extracted data, and assessed risk of bias. The GRADE (Grading of Recommendations Assessment, Development, and Evaluation) approach was used to assess the certainty of evidence. Pooled mean differences (MDs) and 95% CIs were calculated with the use of a random-effects model.

Results

Thirty-three RCTs and 3 CCTs (n = 2161) were included. Glycated hemoglobin declined more in people who consumed low-carbohydrate food than in those who consumed low-fat food in the short term (MD: -1.38%; 95% CI: -2.64%, -0.11%; very-low-certainty evidence). At 1 y, the MD was reduced to -0.36% (95% CI: -0.58%, -0.14%; low-certainty evidence); at 2 y, the difference had disappeared. There is low to high (majority moderate) certainty for small improvements of unclear clinical importance in plasma glucose, triglycerides, and HDL concentrations favoring low-carbohydrate food at half of the prespecified time points. There was little to no difference in LDL concentration or any of the secondary outcomes (body weight, waist circumference, blood pressure, quality of life) in response to either of the diets (very-low- to high-certainty evidence).

Conclusions

Currently available data provide low- to moderate-certainty evidence that dietary carbohydrate restriction to a maximum of 40% yields slightly better metabolic control of uncertain clinical importance than reduction in fat to a maximum of 30% in people with T2D. This systematic review is registered at http://www.crd.york.ac.uk/PROSPERO/display_record.php?ID=CRD42017052467 as CRD42017052467.

Effect of dietary carbohydrate restriction on glycemic control in adults with diabetes: A systematic review and meta-analysis

Nutrition therapy is considered a key component of diabetes management, yet evidence around the ideal macronutrient composition of the diet remains inconclusive. A systematic review and meta-analysis was performed to assess the effects of carbohydrate-restricted diets (≤45% of total energy) compared to high carbohydrate diets (>45% of total energy) on glycemic control in adults with diabetes mellitus. Six databases were searched for articles published between January 1980 and August 2016. Primary outcome was between-group difference in HbA1c change. Individual effect sizes were standardized, and a meta-analysis performed to calculate pooled effect size using random effects. 25 RCTs involving 2412 participants were included. Carbohydrate-restricted diets, in particular those that restrict carbohydrate to <26% of total energy, produced greater reductions in HbA1c at 3 months (WMD -0.47%, 95% CI: -0.71, -0.23) and 6 months (WMD -0.36%, 95% CI: -0.62, -0.09), with no significant difference at 12 or 24 months. There was no difference between moderately restricted (26-45% of total energy) and high carbohydrate diets at any time point. Although there are issues with the quality of the evidence, this review suggests that carbohydrate-restricted diets could be offered to people living with diabetes as part of an individualised management plan.

Nutritional Ketosis and Mitohormesis: Potential Implications for Mitochondrial Function and Human Health

Impaired mitochondrial function often results in excessive production of reactive oxygen species (ROS) and is involved in the etiology of many chronic diseases, including cardiovascular disease, diabetes, neurodegenerative disorders, and cancer. Moderate levels of mitochondrial ROS, however, can protect against chronic disease by inducing upregulation of mitochondrial capacity and endogenous antioxidant defense. This phenomenon, referred to as mitohormesis, is induced through increased reliance on mitochondrial respiration, which can occur through diet or exercise. Nutritional ketosis is a safe and physiological metabolic state induced through a ketogenic diet low in carbohydrate and moderate in protein. Such a diet increases reliance on mitochondrial respiration and may, therefore, induce mitohormesis. Furthermore, the ketone β-hydroxybutyrate (BHB), which is elevated during nutritional ketosis to levels no greater than those resulting from fasting, acts as a signaling molecule in addition to its traditionally known role as an energy substrate. BHB signaling induces adaptations similar to mitohormesis, thereby expanding the potential benefit of nutritional ketosis beyond carbohydrate restriction. This review describes the evidence supporting enhancement of mitochondrial function and endogenous antioxidant defense in response to nutritional ketosis, as well as the potential mechanisms leading to these adaptations.

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.

Effects of Macronutrient Distribution on Weight and Related Cardiometabolic Profile in Healthy Non-Obese Chinese: A 6-month, Randomized Controlled-Feeding Trial

Background

It has been suggested that the increase in carbohydrate at the expense of fat has contributed to the obesity epidemic in North America and some European countries. However, obesity rates in China have increased rapidly in parallel with a transition from the traditional low fat, high carbohydrate diet to a diet relatively high in fat and reduced in carbohydrate. Therefore, the current study aimed to determine whether the traditional Chinese diet was likely to be more effective than a diet with higher fat and lower carbohydrate — which is consumed in most Western societies, at weight control among a non-obese healthy population in China.

Methods

The 6-month, two-center, three-arm, randomized, parallel-group, controlled-feeding trial was conducted at People's Liberation Army General Hospital in north China and Zhejiang University in south China. We recruited healthy young adults (aged 18–35 years, body mass index < 28) who lived in the university campus or the hospital dormitory during the whole study intervention period. They were required to eat only the foods provided, and to avoid excessive or unusual strenuous exercise during the trial. Participants were simultaneously enrolled and randomized using a computer-generated number (stratified by clinic center, age, sex, and body mass index) by data manager to one of the three isocaloric diets (1:1:1): a lower fat, higher carbohydrate diet (fat 20%, carbohydrate 66% energy); a moderate fat, moderate carbohydrate diet (fat 30%, carbohydrate 56% energy); a higher fat, lower carbohydrate diet (fat 40%, carbohydrate 46% energy). Protein provided 14% energy in all diets. We provided all food and beverages throughout the 6-month intervention. Laboratory personnel were masked to treatment allocation. Body weight was the primary outcome and measured each month. Data were primarily analyzed according to an intention-to-treat approach, supplemented with per-protocol analysis. The study was approved by the Ethics Committee at Zhejiang University. Each participant provided written informed consent. The study was registered at Clinicaltrials.gov, number NCT02355795.

Findings

Between April 30, 2016, and October 30, 2016, 307 participants were randomly assigned to the lower fat diet (n = 101), the moderate fat diet (n = 105) and the higher fat diet (n = 101), and 245 (79.8%) participants completed the study. Reduction in body weight was significantly greater in the lower fat, higher carbohydrate group throughout the intervention (P < 0.001 for the interaction between diet group and time) than in the two other groups. Weight change at 6 months was − 1.6 kg (95% CI − 1.8 to − 1.4) in the lower fat, higher carbohydrate group; − 1.1 kg (95% CI − 1.3 to − 0.9) in the moderate fat, moderate carbohydrate group, and − 0.9 kg (95% CI − 1.1 to − 0.6) in the higher fat, lower carbohydrate group. Reduction in waist circumference, total cholesterol, low-density lipoprotein cholesterol and non-high-density lipoprotein cholesterol on the lower fat, higher carbohydrate group were greater than those observed on the other two diet groups.

Interpretation

A lower fat, relatively higher carbohydrate diet, similar in macronutrient composition to that traditionally eaten in China appears to be less likely to promote excessive weight gain and be associated with a lower cardiometabolic risk profile than a diet more typical of that eaten in Western countries in healthy non-obese Chinese. Findings from studies in European and North American populations suggesting possible benefits of carbohydrate restriction may not apply to people of other ethnicities.

•

A LF-HC diet was associated with a greater weight loss and great reduction in waist circumference than a higher fat, lower carbohydrate diet.

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Cardiometabolic risk profiles were more favorable on the LF-HC diet than on a higher fat, lower carbohydrate diet.

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Measures of glycemia were unchanged throughout the trial, regardless if the macronutrient composition.

This is a controlled-feeding trial to evaluate the effects of altering dietary fat and carbohydrate intake on weight change among non-obese subjects in a country experiencing nutritional transition. All the foods and most beverages were provided in order to maximize dietary targets and reduce other dietary or lifestyle related confounding factors during the intervention period. Our findings in conjunction with all other available evidence suggest that the Chinese population should be discouraged from following the continuing trend towards increasing dietary fat intake at the expense of carbohydrate.

Impact of High-Carbohydrate Diet on Metabolic Parameters in Patients with Type 2 Diabetes

In patients with type 2 diabetes mellitus (T2DM), whether dietary carbohydrates have beneficial or detrimental effects on cardiometabolic risk factors has drawn attention. Although a high-carbohydrate (HC) diet and a low-carbohydrate (LC) diet have gained popularity for several decades, there is scarce review focusing on the effects of HC diet on glucose, lipids and body weight in patients with T2DM. In this review, we examined recently-published literature on the effects of HC diets on metabolic parameters in T2DM. HC diets are at least as effective as LC diets, leading to significant weight loss and a reduction in plasma glucose, HbA1c and low density lipoprotein-cholesterol (LDL-C) levels. The major concern is that HC diets may raise serum triglyceride levels and reduce high density lipoprotein-cholesterol (HDL-C) levels, increasing the risk of cardiovascular disease. However, these untoward effects were not a persistent consequence and may be ameliorated with the consumption of a low glycemic index (GI)/low glycemic load (GL) and high fiber. Carbohydrate intake should be individualized, and low caloric intake remains a crucial factor to improve insulin sensitivity and reduce body weight; however, an HC diet, rich in fiber and with a low GI/GL, may be recommendable in patients with T2DM.

Is the Proportion of Carbohydrate Intake Associated with the Incidence of Diabetes Complications?-An Analysis of the Japan Diabetes Complications Study

The appropriate proportions of macronutritional intake have been controversial in medical nutritional therapy for diabetes, and evidence of the effects of carbohydrate consumption on diabetes complications in prospective settings is sparse. We investigated the relationships between proportions of carbohydrate intake as the % of total energy and diabetes complications in a nationwide cohort of Japanese patients with type 2 diabetes aged 40–70 years with hemoglobin A1c ≥6.5%. The analysis was of 1516 responders to a baseline dietary survey assessed by the Food Frequency Questionnaire based on food groups. Primary outcomes were times to overt nephropathy, diabetic retinopathy, and cardiovascular disease (CVD) after 8 years. Hazard ratios (HRs) for proportions of carbohydrate intake were estimated by Cox regression adjusted for confounders. High carbohydrate intake was significantly related to higher intakes of grain, fruits, and sweets/snacks and lower intakes of soybean and soy products, vegetables, seaweed, meat and processed meat, fish and processed fish, eggs, milk and dairy products, oil, and alcoholic beverages. During the eight-year follow-up, there were 81, 275, and 129 events of overt nephropathy, diabetic retinopathy, and CVD, respectively. After adjustment for confounders, HRs for complications in patients with carbohydrate intake in the second or third tertiles (51.0%–56.4% and ≥56.5%, respectively) compared with carbohydrate intake in the first tertile (<50.9%, referent) were analyzed. No significant associations were shown in the second and third tertiles relative to first tertile (overt nephropathy: 1.05 (95% Confidence Interval, 0.54–2.06) and 0.98 (0.40–2.44); diabetic retinopathy: 1.30 (0.90–1.88) and 1.30 (0.78–2.15); and CVD: 0.95 (0.55–1.63) and 1.37 (0.69–2.72)). By exploring potentially nonlinear relationships, trends for the incidence of diabetes complications according to proportions of carbohydrate intake were not clearly shown. Findings suggested that proportions of carbohydrate intake were not associated with the incidence of diabetes complications among type 2 diabetes patients in Japan.

Systematic review and meta-analysis of dietary carbohydrate restriction in patients with type 2 diabetes

OBJECTIVE

Nutrition therapy is an integral part of self-management education in patients with type 2 diabetes. Carbohydrates with a low glycemic index are recommended, but the ideal amount of carbohydrate in the diet is unclear. We performed a meta-analysis comparing diets containing low to moderate amounts of carbohydrate (LCD) (energy percentage below 45%) to diets containing high amounts of carbohydrate (HCD) in subjects with type 2 diabetes.

RESEARCH DESIGN AND METHODS

We systematically reviewed Cochrane library databases, EMBASE, and MEDLINE in the period 2004-2014 for guidelines, meta-analyses, and randomized trials assessing the outcomes HbA1c, BMI, weight, LDL cholesterol, quality of life (QoL), and attrition.

RESULTS

We identified 10 randomized trials comprising 1376 participants in total. In the first year of intervention, LCD was followed by a 0.34% lower HbA1c (3.7 mmol/mol) compared with HCD (95% CI 0.06 (0.7 mmol/mol), 0.63 (6.9 mmol/mol)). The greater the carbohydrate restriction, the greater the glucose-lowering effect (R=-0.85, p<0.01). At 1 year or later, however, HbA1c was similar in the 2 diet groups. The effect of the 2 types of diet on BMI/body weight, LDL cholesterol, QoL, and attrition rate was similar throughout interventions.

LIMITATIONS

Glucose-lowering medication, the nutrition therapy, the amount of carbohydrate in the diet, glycemic index, fat and protein intake, baseline HbA1c, and adherence to the prescribed diets could all have affected the outcomes.

CONCLUSIONS

Low to moderate carbohydrate diets have greater effect on glycemic control in type 2 diabetes compared with high-carbohydrate diets in the first year of intervention. The greater the carbohydrate restriction, the greater glucose lowering, a relationship that has not been demonstrated earlier. Apart from this lowering of HbA1c over the short term, there is no superiority of low-carbohydrate diets in terms of glycemic control, weight, or LDL cholesterol.

Effect of carbohydrate restriction in the first meal after an overnight fast on glycemic control in people with type 2 diabetes: a randomized trial

BACKGROUND

People with type 2 diabetes are advised to consume an even meal distribution of carbohydrate. Whether this distribution is optimal is unknown.

OBJECTIVE

Our objective was to show that omitting carbohydrate in the first meal after a fast would lead to an augmented lunch response.

DESIGN

Two diets of 1-d duration that differed only in the breakfast-meal composition (carbohydrate or no carbohydrate) were consumed on sequential days in a randomized crossover study. The procedure was repeated in the alternate order 1 wk later. Blood glucose concentrations were tested with the use of continuous glucose monitoring. The primary endpoints were the percentage of time spent with a blood glucose concentration >10 mmol/L (%T >10) and peak blood glucose (G_max). The following 45 adults with type 2 diabetes were recruited: subjects with glycated hemoglobin (HbA1c) ≤7% and subjects with HbA1c ≥8%. Twenty-eight adults completed the study.

RESULTS

The daily G_max was significantly lower after the no-carbohydrate breakfast than after the carbohydrate breakfast (11.0 ± 0.4 and 12.1 ± 0.4 mmol/L, respectively; P = 0.003) whereas the %T >10 throughout the day was a nonsignificant 22% less after the no-carbohydrate breakfast than after the carbohydrate breakfast (13% ± 10% compared with 10% ± 8%; P = 0.09). G_max over 5 h after breakfast was significantly lower after the no-carbohydrate meal (by 1.9 ± 0.4 mmol/L; P < 0.001), and the %T >10 was lower after the no-carbohydrate meal than after the carbohydrate meal (11% ± 3% compared with 26% ± 4%, respectively; P < 0.001).

CONCLUSIONS

The withholding of carbohydrate in the first meal results in significantly decreased G_max after the meal, but the lunch response is not affected. Overall daily control is not significantly improved. This trial was registered at the Australian New Zealand Clinical Trials Registry as ACTRN12609000331235.

Comparative effects of carbohydrate versus fat restriction on metabolic profiles, biomarkers of inflammation and oxidative stress in overweight patients with Type 2 diabetic and coronary heart disease: A randomized clinical trial

BACKGROUND

This study was conducted to establish the comparative effects of carbohydrate versus fat restriction on metabolic indices in Type 2 diabetic (T2D) patients with coronary heart disease (CHD).

METHODS

This randomized, clinical trial was done among 56 overweight persons with T2D and CHD aged 40-85 years old. The patients were randomly allocated to take either a high-carbohydrate (HC) diet (60-65% carbohydrates and 20-25% fats) (n = 28) or a restricted carbohydrate (RC) diet (43-49% carbohydrate and 36-40% fats) (n = 28) for 8 weeks to determine metabolic status.

RESULTS

After 8 weeks of treatment, RC diet decreased fasting plasma glucose (FPG) (-11.5 ± 28.3 vs. +7.0 ± 26.9 mg/dl, P = 0.010) and high-sensitivity C-reactive protein (hs-CRP) (-564.3 ± 1280.1 vs. +286.1 ± 1789.2 ng/ml, P = 0.040) compared with a HC diet. Moreover, compared with a HC diet, RC diet increased total antioxidant capacity (TAC) (+274.8 ± 111.5 vs. +20.2 ± 82.5 mmol/l, P < 0.001) and glutathione (GSH) levels (+51.6 ± 111.5 vs. -32.6 ± 88.5 µmol/l, P = 0.003). No significant alterations between the two groups were found in terms of their effect on other metabolic profiles.

CONCLUSION

RC diet in overweight T2D with CHD had beneficial effects on FPG, hs-CRP, TAC, and GSH values.

Cardiometabolic Syndrome and Increased Risk of Heart Failure

Approximately 50 % of patients with heart failure have diastolic heart failure (HFPEF) with the major predisposing risk factors age, inactivity, obesity, insulin resistance (IR), type-2 diabetes, and hypertension. The prognosis of HFPEF is comparable to that of systolic heart failure, but without any specific or effective treatment. This review presents a biomathematically corrected diagnostic approach for quantification of diastolic dysfunction (DD) via the age dependency of diastolic function. Pathophysiological mechanisms for DD in the cardiometabolic syndrome (CMS) are mainly based on downstream effects of IR including insufficient myocardial energy supply. The second section discusses therapeutic strategies for the control and therapy of CMS, IR, and the associated DD/HFPEF with a focus on dietary therapy that is independent of weight loss but improves all manifestations of the CMS and reduces cardiovascular risk.

Macronutrient Composition and Management of Non-Insulin-Dependent Diabetes Mellitus (NIDDM): A New Paradigm for Individualized Nutritional Therapy in Diabetes Patients

Medical nutrition therapy constitutes an important lifestyle intervention in diabetes management. Several nutrition patterns have been effective in improving diabetes control, but there has been a debate about the optimal macronutrient composition in diabetes meal planning. For many years, the recommended diets for persons with and without diabetes were similar, i.e. heart-healthy and low in fat. For almost three decades, carbohydrates have been lauded, lipids demonized, and proteins considered of little importance. However, in the past few years, this concept has been questioned and reassessed. Modern nutritional recommendations for people with diabetes are headed towards individualization, but lack specific guidelines. Nutritional algorithms may help nutritionists in diabetes meal planning. This review aims to discuss: 1) the effects of the three major macronutrients (carbohydrates, proteins, and lipids) on glucose levels, 2) current recommendations for macronutrient intake for people with diabetes, and 3) specific parameters that need to be taken into consideration when determining the macronutrient composition for a person with diabetes, for example body mass index, degree of insulin resistance, HbA1c value, and lipid profile (especially triglycerides and HDL cholesterol). These aspects are analyzed in the context of the results of recent studies, especially randomized controlled trials (RCTs). Finally, we introduce an individualized nutritional concept that proposes carbohydrate over lipid restriction, substitution of SFAs with MUFAs and PUFAs, and adequate intake of dietary fiber, which are key factors in optimizing diabetes management.

Comparison of acarbose and metformin therapy in newly diagnosed type 2 diabetic patients with overweight and/or obesity

OBJECTIVE

To compare the efficacy of acarbose and metformin in overweight and/or obese patients with newly diagnosed type 2 diabetes mellitus (T2DM).

METHODS

A total of 108 drug-naïve patients with newly diagnosed T2DM, whose hemoglobin A1c (HbA1c) was between 7% and 10% and body mass index was greater than 24 kg/m(2), were enrolled in the First People's Hospital and Municipal Central Hospital of Xiangtan City, Xiangtan, China, from 1 February 2010 to 1 August 2011. Patients were randomly assigned to acarbose (100 mg three times a day) and metformin (1.5 g/day) groups for a predictive follow-up period of 24 weeks. Plasma glucose, insulin, and glucagons at 0, 0.5, and 2 hours after a standardized meal, and HbA1c were measured at baseline and 24 weeks.

RESULTS

Baseline characteristics of the acarbose and metformin groups were similar. Glucose control improved significantly in both groups at 24 weeks. The percentage of patients achieving HbA1C <6.5% was comparable for acarbose and metformin therapy at 24 weeks. Body weight reduction from baseline to 24 weeks was 3.3 kg in the acarbose group and 2.7 kg in the metformin group, whereas the change in HbA1c and body weight was similar in both groups. The early-phase insulin secretion index improved only in the acarbose group at 24 weeks. After 24 weeks of therapy, fasting glucagon and 0.5 hour postprandial glucagon levels decreased markedly in the acarbose group compared to the metformin group.

CONCLUSIONS

Twenty-four weeks of therapy with acarbose and metformin induced similar reductions in HbA1c and body weight, but acarbose showed superior efficacy in improving islet α-cell function compared with metformin in overweight/obese patients with newly diagnosed T2DM. However, more large-sample, multicenter, randomized controlled trials are needed to evaluate the efficacy, safety, cost-effectiveness, and glycemic variability of the two drugs.