A low-carbohydrate diet is more effective in reducing body weight than healthy eating in both diabetic and non-diabetic subjects

Methodological Challenges and Confounders in Research on the Effects of Ketogenic Diets: A Literature Review of Meta-Analyses

Several meta-analyses have found a positive association between a popular type of "fad diet", ketogenic diets, and their effect on anthropometric and blood parameters. However, the non-specific inclusion criteria for meta-analyses may lead to incorrect conclusions. The aim of this literature review is to highlight the main confounders and methodological pitfalls of meta-analyses on ketogenic diets by inspecting the presence of key inclusion criteria. The PubMed, Embase, and Web of Science databases and the Cochrane Database of Systematic Reviews were searched for meta-analyses. Most meta-analyses did not define the essential parameters of a ketogenic diet (i.e., calories, macronutrient ratio, types of fatty acids, ketone bodies, etc.) as inclusion criteria. Of the 28 included meta-analyses, few addressed collecting real, re-measured nutritional data from the ketogenic diet and control groups in parallel with the pre-designed nutritional data. Most meta-analyses reported positive results in favor of ketogenic diets, which can result in erroneous conclusions considering the numerous methodological pitfalls and confounders. Well-designed clinical trials with comparable results and their meta-analyses are needed. Until then, medical professionals should not recommend ketogenic diets as a form of weight loss when other well-known dietary options have been shown to be healthy and effective.

The effects of the ketogenic diet for the management of type 2 diabetes mellitus: A systematic review and meta-analysis of recent studies

OBJECTIVE

To systematically review the effects of the ketogenic diet on glycaemic control, body weight, cardiovascular risk factors, and liver and kidney function in patients with type 2 diabetes.

METHODS

PubMed, MEDLINE, Embase, Cochrane Library and CINAHL were searched for randomised controlled trials published between 2001 and 2021 that compared the ketogenic diet to a control diet for effects on glycaemic control, body weight, cardiovascular risk factors, liver and renal function markers in adults with type 2 diabetes for >14 days. Meta-analyses using fixed or random effects models were conducted.

RESULTS

Nineteen reports from 11 randomised controlled trials were included. Compared to the control, the ketogenic diet showed no significant difference in changes in glycaemic control or body weight, but greater increases in HDL (standardised mean difference 0.19; 95%CI 0.02-0.37; I2 = 0 %; moderate-quality evidence) and greater reductions in triglycerides (standardised mean difference -0.41; 95%CI -0.64 to -0.18; I2 = 0 %; low-quality evidence).

CONCLUSIONS

The ketogenic diet may improve lipid profiles but showed no additional benefits for glycaemic control or weight loss compared to control diets in type 2 diabetes patients over two years.

Effects of a low-carbohydrate diet in adults with type 1 diabetes management: A single arm non-randomised clinical trial

Public interest in low-carbohydrate (LC) diets for type 1 diabetes (T1D) management has increased. This study compared the effects of a healthcare professional delivered LC diet compared to habitual diets higher in carbohydrates on clinical outcomes in adults with T1D. Twenty adults (18-70 yrs) with T1D (≥6 months duration) with suboptimal glycaemic control (HbA1c>7.0% or >53 mmol/mol) participated in a 16-week single arm within-participant, controlled intervention study involving a 4-week control period following their habitual diets (>150 g/day of carbohydrates) and a 12-week intervention period following a LC diet (25-75 g/day of carbohydrates) delivered remotely by a registered dietitian. Glycated haemoglobin (HbA1c -primary outcome), time in range (blood glucose: 3.5-10.0 mmol/L), frequency of hypoglycaemia (<3.5 mmol/L), total daily insulin, and quality of life were assessed before and after the control and intervention periods. Sixteen participants completed the study. During the intervention period, there were reductions in total dietary carbohydrate intake (214 to 63 g/day; P<0.001), HbA1c (7.7 to 7.1% or 61 to 54 mmol/mol; P = 0.003) and total daily insulin use (65 to 49 U/day; P<0.001), increased time spent in range (59 to 74%; P<0.001), and improved quality of life (P = 0.015), with no significant changes observed during the control period. Frequency of hypoglycaemia episodes did not differ across timepoints, and no episodes of ketoacidosis or other adverse events were reported during the intervention period. These preliminary findings suggest that a professionally supported LC diet may lead to improvements in markers of blood glucose control and quality of life with reduced exogenous insulin requirements and no evidence of increased hypoglycaemia or ketoacidosis risk in adults with T1D. Given the potential benefits of this intervention, larger, longer-term randomised controlled trials are warranted to confirm these findings. Trial Registration: https://www.anzctr.org.au/ACTRN12621000764831.aspx.

Impact of Body Composition on Sleep and Its Relationship with Sleep Disorders: Current Insights

Sleep is involved in many physiological processes and is essential for both physical and mental health. Obesity and sleep deprivation due to sleep disorders are major public health issues. Their incidence is increasing, and they have a wide range of adverse health-related consequences, including life-threatening cardiovascular disease. The impact of sleep on obesity and body composition is well-known, and many studies have shown an association between insufficient or excessive sleep duration and obesity, body fat percentage, and weight gain. However, there is growing evidence of the effects of body composition on sleep and sleep disorders (particularly sleep disordered breathing) through anatomical and physiological mechanisms (nocturnal fluid shift, core body temperature, or diet). Although some research has been conducted on the bidirectional effects of sleep-disordered breathing and body composition, the specific effects of obesity and body composition on sleep and the underlying mechanisms that explain these effects remain unclear. Therefore, this review summarizes the findings on the effects of body composition on sleep and draws conclusions and proposals for future research in this field.

Effect of calorie restriction in comparison to usual diet or usual care on remission of type 2 diabetes: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Limited evidence is available about the dose-dependent effects of calorie restriction in patients with type 2 diabetes.

OBJECTIVE

To gather available evidence on the effect of calorie restriction on management of type 2 diabetes.

METHODS

We systematically searched PubMed, Scopus, CENTRAL, Web of Science, and gray literature to November 2022 for randomized trials longer than 12 weeks looking at the effect of a pre-specified calorie-restricted diet on remission of type 2 diabetes. We performed random-effects meta-analyses to estimate the absolute effect (risk difference) at 6-month (6±3 months) and 12-month (12±3 months) follow-ups. We performed dose-response meta-analyses to estimate mean difference (MD) for the effects of calorie restriction on cardiometabolic outcomes. We used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to judge the certainty of evidence.

RESULTS

28 randomized trials with 6281 participants were included. Using a remission definition of glycated hemoglobin (HbA_1c) <6.5% without antidiabetic medication use, calorie-restricted diets increased remission by 38 more per 100 patients (95%CI: 9 more, 67 more; n=5 trials, GRADE=moderate) at 6-month, and by 13 more per 100 patients (95%CI: 10 more, 18 more; n=4, GRADE=moderate) at 12-month in comparison to usual diet or usual care. Using a definition of HbA_1c<6.5% after at least two months cessation of antidiabetic medications, remission increased by 34 more per 100 patients (95%CI: 15 more, 53 more; n=1, GRADE=very low) at 6-month and by 16 more per 100 patients (95%CI: 4 more, 49 more; n=2, GRADE=low) at 12-month. At 6-month, each 500 kcal/day decrease in energy intake resulted in clinically meaningful reductions in body weight (MD: -6.33 kg, 95%CI: -7.76, -4.90; n=22; GRADE=high) and HbA_1c (MD: -0.82%, 95%CI: -1.05, -0.59; n=18, GRADE=high), which attenuated remarkably at 12-month.

CONCLUSIONS

Calorie-restricted diets may be effective interventions for type 2 diabetes remission, especially when coupled with an intensive lifestyle modification program.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO (CRD42022300875).

Very low carbohydrate (ketogenic) diets in type 2 diabetes: A systematic review and meta-analysis of randomized controlled trials

AIM

Very low carbohydrate/ketogenic diets (VLC/KDs) are popular but their role in managing pre-diabetes and type 2 diabetes (T2D) is uncertain. This study uses a systematic review and meta-analysis of randomized controlled trials to estimate the effect of these diets in this population.

MATERIALS AND METHODS

A systematic review identified randomized controlled trials of at least 6 months duration comparing efficacy and safety of VLC/KDs (≤50 g carbohydrate or ≤10% total energy from carbohydrate per day) with a control diet (carbohydrate above the VLC/KD threshold) in adults with pre-diabetes or T2D. The primary outcome variable was glycated haemoglobin (HbA1c) after 12 months. The meta-analysis method was inverse variance weighting of mean values for continuous variables.

RESULTS

Key word searches identified 2290 studies; 2221 were not in scope. A full text review of 69 studies identified eight meeting inclusion criteria; in total, it involved 606 participants. Six studies reported HbA1c (%) at 12 months; four as change from baseline with a fixed effects estimate (95% confidence interval): VLC/KD minus control of 0.01% (-0.22 to 0.25), p = .91; and two as change from baseline: -0.65% (-0.99; -0.31) [-7.1 mmol/mol (-10.8; -3.4)], p < .001. Serum triglycerides were lower with VLC/KD versus control: -0.28 mmol/L (-0.44 to -0.11), p < .001. High-density lipoprotein was higher with an estimate of 0.04 mmol/L (0.01 to 0.08), p = .03, in the five studies reporting 12-month summary data.

CONCLUSIONS

A VLC/KD may cause reductions in HbA1c and triglycerides in those with pre-diabetes or T2D but evidence of an advantage over other strategies is limited. More well-designed studies are required to provide certain evidence.

A Health Care Professional Delivered Low Carbohydrate Diet Program Reduces Body Weight, Haemoglobin A1c, Diabetes Medication Use and Cardiovascular Risk Markers-A Single-Arm Intervention Analysis

This study examined the effectiveness of a health care professional delivered low-carbohydrate diet program (Diversa Health Program) aiming to improve obesity/type-2-diabetes management for people living in Australia. 511 adults (Age:57.1 ± 13.7 [SD] yrs) who participated between January 2017−August 2021 for ≥30 days with pre-post data collected for ≥1 key outcome variable (body weight and HbA1c) were included in the analysis. Average participation duration was 218 ± 207 days with 5.4 ± 3.9 reported consultation visits. Body weight reduced from 92.3 ± 23.0 to 86.3 ± 21.1 kg (n = 506, p < 0.001). Weight loss was 0.9 ± 2.8 kg (1.3%), 4.5 ± 4.3 kg (5.7%) and 7.9 ± 7.2 kg (7.5%), respectively, for those with a classification of normal weight (n = 67), overweight (n = 122) and obese (n = 307) at commencement. HbA1c reduced from 6.0 ± 1.2 to 5.6 ± 0.7% (n = 212, p < 0.001). For members with a commencing HbA1c of <5.7% (n = 110), 5.7−6.4% (n = 55), and ≥6.5% (n = 48), HbA1c reduced −0.1 ± 0.2%, −0.3 ± 0.3%, and −1.4 ± 1.3%, respectively. For members with a commencing HbA1c ≥6.5%, 90% experienced a HbA1c reduction and 54% achieved a final HbA1c < 6.5%. With inclusion and exclusion of metformin, respectively, 124 and 82 diabetes medications were prescribed to 63 and 42 members that reduced to 82 and 35 medications prescribed to 51 and 26 members at final visit. A health care professional delivered low-carbohydrate diet program can facilitate weight loss and improve glycaemic control with greatest improvements and clinical relevance in individuals with worse baseline parameters.

The Harry Keen Rank Nutrition Lecture 2022. Nutritional guidelines for diabetes management: Where do they come from and do they work?

Nutritional guidelines for diabetes are designed to support those living with diabetes in achieving optimal glycaemic control, reducing the risk of cardiovascular disease and maintaining quality of life. Historically, guidelines reflected current opinion and clinical practice and only relatively recently have evidence-based recommendations been published. Current nutritional guidelines for type 1 and type 2 diabetes are based on high-quality evidence including data from randomised controlled trials and prospective cohort studies and are graded by the strength of evidence. There is no evidence to support one specific dietary strategy for people with diabetes, and this is particularly true for weight reduction in those with type 2 diabetes living with overweight or obesity, where the evidence suggests that different strategies are equally successful. As a result, the emphasis of modern guidelines is on individualised, person-centred approaches. Some barriers to successful implementation include lack of dietary education and knowledge in health professionals supporting people with diabetes, and a so-called obesogenic environment that impedes dietary change. Initiatives such as education and training programmes for health professionals, and population-based interventions that promote both structural and policy change are recommended to enable those with diabetes to support dietary change and improve health.

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.

Effect of Carbohydrate-Restricted Diets and Intermittent Fasting on Obesity, Type 2 Diabetes Mellitus, and Hypertension Management: Consensus Statement of the Korean Society for the Study of Obesity, Korean Diabetes Association, and Korean Society of Hypertension

Carbohydrate-restricted diets and intermittent fasting (IF) have been rapidly gaining interest among the general population and patients with cardiometabolic disease, such as overweight or obesity, diabetes, and hypertension. However, there are limited expert recommendations for these dietary regimens. This study aimed to evaluate the level of scientific evidence on the benefits and harms of carbohydrate-restricted diets and IF to make responsible recommendations. A meta-analysis and systematic literature review of 66 articles on 50 randomized controlled trials (RCTs) of carbohydrate-restricted diets and 10 articles on eight RCTs of IF was performed. Based on the analysis, the following recommendations are suggested. In adults with overweight or obesity, a moderately-low carbohydrate or low carbohydrate diet (mLCD) can be considered as a dietary regimen for weight reduction. In adults with type 2 diabetes mellitus, mLCD can be considered as a dietary regimen for improving glycemic control and reducing body weight. In contrast, a very-low carbohydrate diet (VLCD) and IF are recommended against in patients with diabetes. Furthermore, no recommendations are suggested for VLCD and IF in adults with overweight or obesity, and carbohydrate-restricted diets and IF in patients with hypertension. Here, we describe the results of our analysis and the evidence for these recommendations.

Reversal and Remission of T2DM - An Update for Practitioners

Over the past 50 years, many countries around the world have faced an unchecked pandemic of obesity and type 2 diabetes (T2DM). As best practice treatment of T2DM has done very little to check its growth, the pandemic of diabesity now threatens to make health-care systems economically more difficult for governments and individuals to manage within their budgets. The conventional view has been that T2DM is irreversible and progressive. However, in 2016, the World Health Organization (WHO) global report on diabetes added for the first time a section on diabetes reversal and acknowledged that it could be achieved through a number of therapeutic approaches. Many studies indicate that diabetes reversal, and possibly even long-term remission, is achievable, belying the conventional view. However, T2DM reversal is not yet a standardized area of practice and some questions remain about long-term outcomes. Diabetes reversal through diet is not articulated or discussed as a first-line target (or even goal) of treatment by any internationally recognized guidelines, which are mostly silent on the topic beyond encouraging lifestyle interventions in general. This review paper examines all the sustainable, practical, and scalable approaches to T2DM reversal, highlighting the evidence base, and serves as an interim update for practitioners looking to fill the practical knowledge gap on this topic in conventional diabetes guidelines.

Effect of carbohydrate-restricted diets and intermittent fasting on obesity, type 2 diabetes mellitus, and hypertension management: consensus statement of the Korean Society for the Study of obesity, Korean Diabetes Association, and Korean Society of Hypertension

BACKGROUND

Carbohydrate-restricted diets and intermittent fasting (IF) have been rapidly gaining interest among the general population and patients with cardiometabolic disease, such as overweight or obesity, diabetes, and hypertension. However, there are limited expert recommendations for these dietary regimens. This study aimed to evaluate the level of scientific evidence on the benefits and harms of carbohydrate-restricted diets and IF to make responsible recommendations.

METHODS

A meta-analysis and systematic literature review of 66 articles on 50 randomized controlled clinical trials (RCTs) of carbohydrate-restricted diets and ten articles on eight RCTs of IF was performed.

RESULTS

Based on the analysis, the following recommendations are suggested. In adults with overweight or obesity, a moderately-low carbohydrate or low carbohydrate diet (mLCD) can be considered as a dietary regimen for weight reduction. In adults with type 2 diabetes, mLCD can be considered as a dietary regimen for improving glycemic control and reducing body weight. In contrast, a very-low carbohydrate diet (VLCD) and IF are recommended against in patients with diabetes. Furthermore, no recommendations are suggested for VLCD and IF in adults with overweight or obesity, and carbohydrate-restricted diets and IF in patients with hypertension.

CONCLUSION

Here, we describe the results of our analysis and the evidence for these recommendations.

A Comparative Study Evaluating the Effectiveness Between Ketogenic and Low-Carbohydrate Diets on Glycemic and Weight Control in Patients With Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis

Diabetes mellitus (DM) has become a worldwide public health burden and a significant cause of motility and morbidity. The most common type of diabetes is type 2 diabetes, which is estimated to have a prevalence of one in every ten adults living with diabetes in the United States. The risk factors for type 2 diabetes are obesity and being overweight. Therefore, the primary strategy used to manage type 2 diabetes is weight loss. Different measures, such as dietary therapies and physical training, have been used to manage type 2 diabetes through weight and glycemic control. The dietary therapies used to manage type 2 diabetes are ketogenic and low-carbohydrate diets. Despite studies showing that both ketogenic and low-carbohydrate diets significantly impact weight and glycemic control, the difference between the two diets has not been fully established. Therefore, this systematic review has demonstrated and compared the effectiveness of ketogenic and low-carbohydrate diets on glycemic and weight control.

The literature search was conducted on five electronic databases, PubMed, ScienceDirect, Embase, Web of Science, and Google Scholar, from 2000 to 2022. Specified keywords related to the ketogenic diet (KD), low carbohydrates, and type 2 diabetes were used to search for relevant and original articles. The identified articles were analyzed using the eligibility criteria before they were included in the study. The eligibility criteria yielded 15 studies that were included in this systematic review. The results obtained by conducting a meta-analysis showed that low-carbohydrates had a greater reduction in the HbA1c than other diets (standardized mean difference [SMD]: -0.27%; 95% CI; -0.60%, 0.07%: P = 0.008, I2 = 66%). Similarly, a significant decrease in HbA1c percentage was recorded in patients that consumed KDs compared to those who consumed the control diets (SMD: -1.45%; 95% CI; -2.73%, -0.17%: P < 0.00001). The results also show that the KD significantly impacts weight loss than control diets.

The results show that the KD is more effective in reducing glycated haemoglobin and body weight (BW) than a low-carbohydrate diet. Therefore, we can summarize that the KD is a more effective dietary therapy. However, there is a need to balance the weight loss and glycemic control benefits obtained from the KD with the increased cardiovascular risks for patients with type 2 diabetes.

Comprehensive Understanding for Application in Korean Patients with Type 2 Diabetes Mellitus of the Consensus Statement on Carbohydrate-Restricted Diets by Korean Diabetes Association, Korean Society for the Study of Obesity, and Korean Society of Hypertension

The Joint Committee of the Korean Diabetes Association, the Korean Society for the Study of Obesity, and the Korean Society of Hypertension announced a consensus statement on carbohydrate-restricted diets and intermittent fasting, representing an emerging and popular dietary pattern. In this statement, we recommend moderately-low-carbohydrate or low-carbohydrate diets, not a very-low-carbohydrate diet, for patients with type 2 diabetes mellitus. These diets can be considered a dietary regimen to improve glycemic control and reduce body weight in adults with type 2 diabetes mellitus. This review provides the detailed results of a meta-analysis and systematic literature review on the potential harms and benefits of carbohydrate-restricted diets in patients with diabetes. We expect that this review will help experts and patients by fostering an in-depth understanding and appropriate application of carbohydrate-restricted diets in the comprehensive management of diabetes.

Effect of Carbohydrate-Restricted Diets and Intermittent Fasting on Obesity, Type 2 Diabetes Mellitus, and Hypertension Management: Consensus Statement of the Korean Society for the Study of Obesity, Korean Diabetes Association, and Korean Society of Hypertension

Carbohydrate-restricted diets and intermittent fasting (IF) have been rapidly gaining interest among the general population and patients with cardiometabolic disease, such as overweight or obesity, diabetes, and hypertension. However, there are limited expert recommendations for these dietary regimens. This study aimed to evaluate the level of scientific evidence on the benefits and harms of carbohydrate-restricted diets and IF to make responsible recommendations. A meta-analysis and systematic literature review of 66 articles on 50 randomized controlled trials (RCTs) of carbohydrate-restricted diets and 10 articles on eight RCTs of IF was performed. Based on the analysis, the following recommendations are suggested. In adults with overweight or obesity, a moderately-low carbohydrate or low carbohydrate diet (mLCD) can be considered as a dietary regimen for weight reduction. In adults with type 2 diabetes mellitus, mLCD can be considered as a dietary regimen for improving glycemic control and reducing body weight. In contrast, a very-low carbohydrate diet (VLCD) and IF are recommended against in patients with diabetes. Furthermore, no recommendations are suggested for VLCD and IF in adults with overweight or obesity, and carbohydrate-restricted diets and IF in patients with hypertension. Here, we describe the results of our analysis and the evidence for these recommendations.

Low-carbohydrate versus balanced-carbohydrate diets for reducing weight and cardiovascular risk

BACKGROUND

Debates on effective and safe diets for managing obesity in adults are ongoing. Low-carbohydrate weight-reducing diets (also known as 'low-carb diets') continue to be widely promoted, marketed and commercialised as being more effective for weight loss, and healthier, than 'balanced'-carbohydrate weight-reducing diets.

OBJECTIVES

To compare the effects of low-carbohydrate weight-reducing diets to weight-reducing diets with balanced ranges of carbohydrates, in relation to changes in weight and cardiovascular risk, in overweight and obese adults without and with type 2 diabetes mellitus (T2DM).

SEARCH METHODS

We searched MEDLINE (PubMed), Embase (Ovid), the Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science Core Collection (Clarivate Analytics), ClinicalTrials.gov and WHO International Clinical Trials Registry Platform (ICTRP) up to 25 June 2021, and screened reference lists of included trials and relevant systematic reviews. Language or publication restrictions were not applied.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) in adults (18 years+) who were overweight or living with obesity, without or with T2DM, and without or with cardiovascular conditions or risk factors. Trials had to compare low-carbohydrate weight-reducing diets to balanced-carbohydrate (45% to 65% of total energy (TE)) weight-reducing diets, have a weight-reducing phase of 2 weeks or longer and be explicitly implemented for the primary purpose of reducing weight, with or without advice to restrict energy intake.  DATA COLLECTION AND ANALYSIS: Two review authors independently screened titles and abstracts and full-text articles to determine eligibility; and independently extracted data, assessed risk of bias using RoB 2 and assessed the certainty of the evidence using GRADE. We stratified analyses by participants without and with T2DM, and by diets with weight-reducing phases only and those with weight-reducing phases followed by weight-maintenance phases. Primary outcomes were change in body weight (kg) and the number of participants per group with weight loss of at least 5%, assessed at short- (three months to < 12 months) and long-term (≥ 12 months) follow-up.

MAIN RESULTS

We included 61 parallel-arm RCTs that randomised 6925 participants to either low-carbohydrate or balanced-carbohydrate weight-reducing diets. All trials were conducted in high-income countries except for one in China. Most participants (n = 5118 randomised) did not have T2DM. Mean baseline weight across trials was 95 kg (range 66 to 132 kg). Participants with T2DM were older (mean 57 years, range 50 to 65) than those without T2DM (mean 45 years, range 22 to 62). Most trials included men and women (42/61; 3/19 men only; 16/19 women only), and people without baseline cardiovascular conditions, risk factors or events (36/61). Mean baseline diastolic blood pressure (DBP) and low-density lipoprotein (LDL) cholesterol across trials were within normal ranges. The longest weight-reducing phase of diets was two years in participants without and with T2DM. Evidence from studies with weight-reducing phases followed by weight-maintenance phases was limited. Most trials investigated low-carbohydrate diets (> 50 g to 150 g per day or < 45% of TE; n = 42), followed by very low (≤ 50 g per day or < 10% of TE; n = 14), and then incremental increases from very low to low (n = 5). The most common diets compared were low-carbohydrate, balanced-fat (20 to 35% of TE) and high-protein (> 20% of TE) treatment diets versus control diets balanced for the three macronutrients (24/61). In most trials (45/61) the energy prescription or approach used to restrict energy intake was similar in both groups. We assessed the overall risk of bias of outcomes across trials as predominantly high, mostly from bias due to missing outcome data. Using GRADE, we assessed the certainty of evidence as moderate to very low across outcomes.  Participants without and with T2DM lost weight when following weight-reducing phases of both diets at the short (range: 12.2 to 0.33 kg) and long term (range: 13.1 to 1.7 kg).  In overweight and obese participants without T2DM: low-carbohydrate weight-reducing diets compared to balanced-carbohydrate weight-reducing diets (weight-reducing phases only) probably result in little to no difference in change in body weight over three to 8.5 months (mean difference (MD) -1.07 kg, (95% confidence interval (CI) -1.55 to -0.59, I2 = 51%, 3286 participants, 37 RCTs, moderate-certainty evidence) and over one to two years (MD -0.93 kg, 95% CI -1.81 to -0.04, I2 = 40%, 1805 participants, 14 RCTs, moderate-certainty evidence); as well as change in DBP and LDL cholesterol over one to two years. The evidence is very uncertain about whether there is a difference in the number of participants per group with weight loss of at least 5% at one year (risk ratio (RR) 1.11, 95% CI 0.94 to 1.31, I2 = 17%, 137 participants, 2 RCTs, very low-certainty evidence).  In overweight and obese participants with T2DM: low-carbohydrate weight-reducing diets compared to balanced-carbohydrate weight-reducing diets (weight-reducing phases only) probably result in little to no difference in change in body weight over three to six months (MD -1.26 kg, 95% CI -2.44 to -0.09, I2 = 47%, 1114 participants, 14 RCTs, moderate-certainty evidence) and over one to two years (MD -0.33 kg, 95% CI -2.13 to 1.46, I2 = 10%, 813 participants, 7 RCTs, moderate-certainty evidence); as well in change in DBP, HbA1c and LDL cholesterol over 1 to 2 years. The evidence is very uncertain about whether there is a difference in the number of participants per group with weight loss of at least 5% at one to two years (RR 0.90, 95% CI 0.68 to 1.20, I2 = 0%, 106 participants, 2 RCTs, very low-certainty evidence).  Evidence on participant-reported adverse effects was limited, and we could not draw any conclusions about these.  AUTHORS' CONCLUSIONS: There is probably little to no difference in weight reduction and changes in cardiovascular risk factors up to two years' follow-up, when overweight and obese participants without and with T2DM are randomised to either low-carbohydrate or balanced-carbohydrate weight-reducing diets.

The low carb program for people with type 2 diabetes and pre-diabetes - a mixed methods feasibility study of signposting from general practice

Background

Evidence shows type 2 diabetes mellitus (T2DM) can be effectively treated with a reduced-carbohydrate diet to support weight loss. Digital apps are increasingly used to support weight loss, yet little is known about their use as part of general practice diabetes care.

Aim

Determine the feasibility of signposting from routine NHS general practice to a digital weight management tool (Low Carb Program) for patients with T2DM and pre-diabetes.

Design & setting

Mixed-methods feasibility study implemented within routine general practice consultations at four practices in the Midlands, England.

Method

General practices offered signposting to eligible patients attending consultations of any type during a 4-week recruitment period. Rates of offering and accepting signposting were recorded, with program registration, program completion, and self-reported health outcomes (weight, haemoglobin A1C [HbA1c]).

Results

Signposting was offered to 351 patients; 160 (45.6%) accepted, 103 (29.3%) registered with the intervention and 43 (26.9% of patients accepting signposting) completed the programme. GPs reported that signposting added between 1–4 minutes to the consultation length. Patients completing the programme reported greater weight loss (7.2kg versus 1.6kg, P<0.001) and HbA1c improvements (-9.1mmol/mol versus 1.7mmol/mol, P<0.001) compared to those who did not, and were more likely to reduce the number of prescribed diabetes medications in general practice.

Conclusions

Signposting from real-world general practice to the Low CarbProgram is feasible and can potentially improve diabetes outcomes. Further research should explore whether the process of signposting can be enhanced to increase registration, identify whether additional practice-led support leads to increased programme completion, and confirm the intervention’s clinical and cost-effectiveness.

Effect of a very low-carbohydrate ketogenic diet vs recommended diets in patients with type 2 diabetes: a meta-analysis

CONTEXT

There is renewed interest in using very low-carbohydrate ketogenic (VLCK) diets to manage diabetes. Many clinical trials have been published, often with mixed results.

OBJECTIVE

This meta-analysis compares the effect of a VLCK diet on glycemic control, body weight, lipid profile, medication use, and dropouts with that of recommended diets for 12 weeks or longer in people with type 2 diabetes.

DATA SOURCES

Ovid MEDLINE, Ovid Embase, CENTRAL, and CINAHL databases were searched (January 1980 through September 2019).

STUDY SELECTION

Two authors independently reviewed search results to select randomized controlled trials (RCTs) comparing a VLCK diet (carbohydrate intake < 50 g/d or < 10% of total energy) with any recommended diet for type 2 diabetes in adults. Discrepancies were resolved after consulting with the third author.

DATA EXTRACTION

Eight RCTs with 648 participants were identified.

RESULTS

Compared with control diets, the VLCK diet resulted in a greater decrease in hemoglobin A1c after 3 months (weighted mean difference[WMD]: -6.7 mmol/mol; 95%CI, -9.0 to -4.4) (WMD: -0.61%; 95%CI, -0.82 to -0.40; P < 0.001; moderate-certainty evidence) and after 6 months (WMD: -6.3 mmol/mol; 95%CI, -9.3 to -3.5) (WMD: -0.58%; 95%CI, -0.85 to -0.32; low-certainty evidence). There was a significantly greater weight loss with the VLCK diet after 3 months (WMD: -2.91 kg; 95%CI, -4.88 to -0.95; low-certainty evidence) and after 6 months (WMD: -2.84 kg; 95%CI, -5.29 to -0.39; low-certainty evidence). The VLCK diet was not better than a control diet after 12 months. It was superior in decreasing triglyceride levels, increasing high-density lipoprotein cholesterol levels, and reducing the use of antidiabetic medications for up to 12 months.

CONCLUSION

The VLCK diet appears to control glycemia and decrease body weight for up to 6 months in people with obesity and diabetes. Beneficial changes in serum triglycerides and high-density lipoprotein cholesterol, along with reductions in antidiabetic medications, continued in the VLCK group until 12 months. However, the quality of currently available evidence is not sufficient to recommend VLCK diets. A major limitation of the VLCK diet is patients' lack of adherence to carbohydrate restriction.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number CRD42020154700.

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.

The Role of Exercise, Diet, and Cytokines in Preventing Obesity and Improving Adipose Tissue

The prevalence of obesity continues to rise worldwide despite evidence-based public health recommendations. The promise to adopt a healthy lifestyle is increasingly important for tackling this global epidemic. Calorie restriction or regular exercise or a combination of the two is accepted as an effective strategy in preventing or treating obesity. Furthermore, the benefits conferred by regular exercise to overcome obesity are attributed not only to reduced adiposity or reduced levels of circulating lipids but also to the proteins, peptides, enzymes, and metabolites that are released from contracting skeletal muscle or other organs. The secretion of these molecules called cytokines in response to exercise induces browning of white adipose tissue by increasing the expression of brown adipocyte-specific genes within the white adipose tissue, suggesting that exercise-induced cytokines may play a significant role in preventing obesity. In this review, we present research-based evidence supporting the effects of exercise and various diet interventions on preventing obesity and adipose tissue health. We also discuss the interplay between adipose tissue and the cytokines secreted from skeletal muscle and other organs that are known to affect adipose tissue and metabolism.

Islet Health, Hormone Secretion, and Insulin Responsivity with Low-Carbohydrate Feeding in Diabetes

Exploring new avenues to control daily fluctuations in glycemia has been a central theme for diabetes research since the Diabetes Control and Complications Trial (DCCT). Carbohydrate restriction has re-emerged as a means to control type 2 diabetes mellitus (T2DM), becoming increasingly popular and supported by national diabetes associations in Canada, Australia, the USA, and Europe. This approval comes from many positive outcomes on HbA1c in human studies; yet mechanisms underlying their success have not been fully elucidated. In this review, we discuss the preclinical and clinical studies investigating the role of carbohydrate restriction and physiological elevations in ketone bodies directly on pancreatic islet health, islet hormone secretion, and insulin sensitivity. Included studies have clearly outlined diet compositions, including a diet with 30% or less of calories from carbohydrates.

A Systematic Review and Meta-Analysis Comparing Heterogeneity in Body Mass Responses Between Low-Carbohydrate and Low-Fat Diets

OBJECTIVE

An important notion in personalized medicine is that there is clinically relevant treatment response heterogeneity. Low-carbohydrate (CHO) and low-fat diets are widely adopted to reduce body mass. To compare individual differences in responses between two dietary interventions, a formal statistical comparison of response variances between study arms in a randomized controlled trial (RCT) is crucial.

METHODS

The change in variances in RCTs for the body mass responses to low-CHO dietary interventions versus change variances for the low-fat groups (typically considered as the comparator intervention) were compared. A literature search identified relevant RCTs (n = 25; 3,340 participants). The means and SDs of body mass change in low-CHO and low-fat study arms were extracted to calculate the variances of individual responses. These were meta-analyzed in a random-effects model and converted to the SD for individual responses.

RESULTS

The pooled SD for individual responses for body mass was 1.4 kg (95% CI: -1.1 to 2.3) with a wide 95% prediction interval of -6.3 to 10.4 kg.

CONCLUSIONS

Evidence is insufficient to suggest the response heterogeneity to low-CHO diets differs from that observed with low-fat diets.

Lowered blood pressure targets identify new, uncontrolled hypertensive cases: patient characteristics and implications for services in Thailand

BACKGROUND

According to the new hypertension treatment guidelines blood pressure (BP) readings need to be kept below or equal to 130/80 mmHg in patients aged less than 65 years old. This study shows the change in proportion of identified cases of uncontrolled blood pressure in light of these changes.

METHODS

The data was collected from 248 hypertensive patients who had visited an outpatient clinic at the Department of Family Medicine, Faculty of Medicine, Chiang Mai University, Thailand. Patients were classified into three groups: The 3 groups were: 1) controlled BP group (BP is 130/80 mmHg or lower); 2) newly identified uncontrolled group (BP between 130/80 mmHg and 140/90 mmHg) and 3) existing uncontrolled group (BP higher than 140/90 mmHg). Health behaviors, past history related to hypertensive disease and current pharmacological treatments were compared.

RESULTS

Of the total 248 patients, 56% were female and the mean age was 58.8 (sd 5.99) years old. Following application of the new guidelines, the group designated as uncontrolled increased from 21.7 to 74.2%, an additional 52.4% due to new BP targets. Higher BMI was associated with uncontrolled HT (p = 0.043). While the average number of medication taken was similar across the three groups, it was poor medication adherence (p < 0.013) which was associated with the uncontrolled disease.

CONCLUSIONS

Lower BP targets will increase the number of identified hypertensive patients. While intensifying pharmacological treatment may be considered, our study suggests that two behavioral factors should not be overlooked. Weight reduction and enhancement of medication adherence remains an important mainstream treatment strategy.

The Effects of a Low Calorie Ketogenic Diet on Glycaemic Control Variables in Hyperinsulinemic Overweight/Obese Females

Diet is a factor which can influence both glycaemic variables and body mass. The aim of this study was to compare the influence of a 12-week, well-planned, low-calorie ketogenic diet (LCKD) on hyperglycaemic, hyperinsulinemic and lipid profile in adult, overweight or obese females. Ninety-one females who participated in the study were divided into two groups: a LCKD group who followed a hypocaloric ketogenic diet (8% of carbohydrate, 72% of fat and 20% of proteins) (n = 46), and a control group (CG) (n = 45) who continued their typical diet (50% of carbohydrates, 32% of fat and 18% of proteins). Methods: Baseline and post-intervention glucose (Gl), insulin (I), glycated haemoglobin (HbA1c), Homeostatic model assessment HOMA-IR, triglycerides (TG) and high-density cholesterol (HDL-C) were evaluated. Also, body mass (BM), waist circumference (WC), hip circumference (HC) and thigh circumference (TC) were measured. Results: Compared with the CG, there were significant changes observed in the LCKD group regarding all biochemical variables. Also, BM, TC, WC and AC changed significantly in the LCKD group compared with the CG. Conclusions: The 12-week LCKD intervention changed the glucose control variables, body mass, as well as waist, hip and thigh circumferences. A low-calorie ketogenic diet may be recommended for adult females with glucose control variables disturbance and excess body mass.

Cardio-metabolic consequences of dietary carbohydrates: reconciling contradictions using nutritional geometry

Carbohydrates are the major source of dietary energy, but their role in health and disease remains controversial. Recent epidemiological evidence suggests that the increased consumption of carbohydrates is associated with obesity and increased risk of mortality and dietary trials show that carbohydrate restriction leads to weight loss and improved glycaemic status in obese and diabetic subjects. In contrast, the diets of populations with long and healthy lifespans (e.g. traditional Okinawans from Japan) are high in carbohydrate and low in protein, and several clinical and preclinical studies have linked low-carbohydrate-high-protein diets with increased mortality risk. In this paper we attempt to reconcile these contradictory findings by moving beyond traditional single-nutrient analyses to consider the interactions between nutrients on health outcomes. We do so using the Geometric Framework (GF), a nutritional modelling platform that explicitly considers the main and interactive effects of multiple nutrients on phenotypic characteristics. Analysis of human data by GF shows that weight loss and improved cardio-metabolic outcomes under carbohydrate restriction derive at least in part from reduced caloric intake due to the concomitantly increased proportion of protein in the diet. This is because, as in many animals, a specific appetite for protein is a major driver of food intake in humans. Conversely, dilution of protein in the diet leverages excess food intake through compensatory feeding for protein ('protein leverage'). When protein is diluted in the diet by readily digestible carbohydrates and fats, as is the case in modern ultra-processed foods, protein leverage results in excess calorie intake, leading to rising levels of obesity and metabolic disease. However, when protein is diluted in the diet by increased quantities of less readily digestible forms of carbohydrate and fibre, energy balance is maintained and health benefits accrue, especially during middle age and early late-life. We argue that other controversies in carbohydrate research can be resolved using the GF methodology in dietary studies.

An evidence-based approach to developing low-carbohydrate diets for type 2 diabetes management: A systematic review of interventions and methods

AIM

To identify core diet and delivery components of low-carbohydrate (CHO) diets that have demonstrated efficacy for type 2 diabetes (T2D) management.

MATERIALS AND METHODS

MEDLINE, Pre-MEDLINE, EMBASE, CINAHL and the Cochrane Library of Controlled Trials databases were systematically searched from inception until August 18, 2018. Primary intervention studies of low-CHO diets (≤130 g/d or 26% total energy intake [TEI]) were included. Content analysis was performed on the low-CHO diet protocols classified as safe and effective for T2D management.

RESULTS

A total of 41 studies published between 1963 and 2018 were included, of which 40 were classified as safe and effective for inclusion in the primary analysis. Thirteen studies (13/40) were on very-low-CHO diets (<50 g/d), 14/40 included low-CHO diets (≤130 g/d or 26% TEI), and 13/40 were adapted according to participant progress. Thirty-one studies reported a total energy prescription, of which 18/31 encouraged ad libitum intakes. Twenty studies reported a prescribed dietary fat amount, of which 18/20 were unrestricted or high-fat (>35% TEI). Twenty-six studies reported a prescribed dietary protein amount, of which 22 were unrestricted or were high-protein (>25% TEI). The types of dietary CHO, fat and protein recommended were predominantly whole foods. Common delivery methods reported were dietician and/or physician involvement, moderate to high frequency of contact (≥1 session/month) and use of participant self-monitoring.

CONCLUSIONS

Multiple approaches for developing and delivering a low-CHO diet intervention for T2D management are safe and effective. A comprehensive set of core dietary components to consider in the formulation of low-CHO diet protocols were identified for use in clinical practice and to inform evidence-based guidelines for T2D management.

Improving the scientific rigour of nutritional recommendations for adults with type 2 diabetes: A comprehensive review of the American Diabetes Association guideline-recommended eating patterns

AIMS

The global rate of type 2 diabetes (T2D) continues to rise. Guidelines that influence the worldwide treatment of this disease are central to changing this trajectory. We sought in this review to evaluate the appropriateness of sources cited in the American Diabetes Association's (ADA) guidelines on eating patterns for T2D management, identify additional relevant sources, and evaluate the evidence.

MATERIALS AND METHODS

We reviewed the evidence behind the ADA's recommendations on eating patterns in the 2018 and 2019 ADA Standards of Care and the 2014 ADA Nutrition Therapy Recommendations for Adults with Diabetes. Additionally, we conducted a comprehensive search to identify any additional studies not included in the cited evidence. To determine appropriateness of inclusion in the guidelines, the following criteria were applied: 1) it was a clinical trial or systematic review/meta-analysis of clinical trials; 2) it involved persons with T2D; 3) one of the study arms followed one of the eating patterns currently recommended; 4) its reported outcomes included glycaemic control; 5) outcomes were reported separately for persons with T2D.

RESULTS

We found a wide variation in the evidence for each eating pattern. Issues that have hampered the guideline process include: lack of a rigorous literature review, resulting in the omission of pertinent studies; an overreliance on prospective cohort studies; inconsistent standards for evidence; inclusion of studies not on persons with T2D; and bias.

CONCLUSIONS

The ADA Guidelines recommended eating patterns fall short of rigorous standards of scientific review according to state-of-the-art systematic review and guideline creation practices.

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.

[Ketogenic Diet and its Evidence-Based Therapeutic Implementation in Endocrine Diseases]

Ketogenic Diet and its Evidence-Based Therapeutic Implementation in Endocrine Diseases Abstract. Abstract: The ketogenic diet (KD) is a high-fat and very low-carb diet, which has been used primarily for treatment of therapy-resistant epilepsy in children. Implementation of the KD in other target populations is increasingly being discussed. This literature review provides first indications for a clinical benefit of the KD in diabetes mellitus type 2 (T2DM) and polycystic ovarian syndrome (PCOS). In many analysed studies, KD led to significant weight loss and had beneficial effects on lipoprotein profile and insulin resistance. In half of the comparative studies with T2DM, the KD lead to signifiantly greater reductions in HbA1c-levels (HbA1c difference: -0.5 to -1.5 %) compared to reference diets (HbA1c difference: +0.2 to -0.5 %). Nevertheless, study results are too heterogenic for a general recommendation of the KD in this patient population.

Reversing Type 2 Diabetes: A Narrative Review of the Evidence

BACKGROUND

Type 2 diabetes (T2D) has long been identified as an incurable chronic disease based on traditional means of treatment. Research now exists that suggests reversal is possible through other means that have only recently been embraced in the guidelines. This narrative review examines the evidence for T2D reversal using each of the three methods, including advantages and limitations for each.

METHODS

A literature search was performed, and a total of 99 original articles containing information pertaining to diabetes reversal or remission were included.

RESULTS

Evidence exists that T2D reversal is achievable using bariatric surgery, low-calorie diets (LCD), or carbohydrate restriction (LC). Bariatric surgery has been recommended for the treatment of T2D since 2016 by an international diabetes consensus group. Both the American Diabetes Association (ADA) and the European Association for the Study of Diabetes (EASD) now recommend a LC eating pattern and support the short-term use of LCD for weight loss. However, only T2D treatment, not reversal, is discussed in their guidelines.

CONCLUSION

Given the state of evidence for T2D reversal, healthcare providers need to be educated on reversal options so they can actively engage in counseling patients who may desire this approach to their disease.

Dietary survey in Japanese patients with type 2 diabetes and the influence of dietary carbohydrate on glycated hemoglobin: The Sleep and Food Registry in Kanagawa study

AIMS/INTRODUCTION

The present study investigated the relationship between the macronutrient energy ratio, dietary carbohydrate and glycated hemoglobin levels in Japanese patients with type 2 diabetes, to generate a potential optimal dietary intake of macronutrients for such patients.

MATERIALS AND METHODS

In total, 3,032 patients participating in the Sleep and Food Registry in Kanagawa study were evaluated. Their diets were assessed for macronutrient content through a brief self-administered dietary history questionnaire. Relevant biochemical assays were carried out.

RESULTS

The mean energy intake (±standard deviation) was 1,711 ± 645 kcal/day. The proportion of energy supplied by protein, fat and carbohydrate were 16.3, 26.8 and 52.3%, respectively. Total fiber intake was 12.6 ± 5.7 g/day. The high glycated hemoglobin (HbA1c) group (HbA1c >8%) had significantly lower protein and higher carbohydrate intake than the low HbA1c group (HbA1c <6.5%). Higher HbA1c levels were positively correlated with unfavorable metabolic factors, including elevated body mass index and excess carbohydrate intake, and negatively correlated with age, protein intake and fiber intake. Multiple regression analysis showed a significant association between HbA1c and carbohydrate intake after adjusting for sex, age and body mass index (0.104, P < 0.0001). Additionally, patients within the uppermost tertile for the percentage of total energy intake from carbohydrate (>60%) were most likely to have high HbA1c levels. HbA1c was significantly correlated with carbohydrate (%E) in all age groups and in patients taking one or two antidiabetic drugs.

CONCLUSIONS

The dietary carbohydrate:energy ratio has a positive correlation with HbA1c, suggesting that avoiding excessive carbohydrate intake (>60%) might help foster glycemic control.

Carbohydrate restriction for glycaemic control in Type 2 diabetes: a systematic review and meta-analysis

AIM

To conduct a systematic review and meta-analysis to evaluate the effect of carbohydrate restriction on glycaemic control in Type 2 diabetes.

METHODS

We searched Medline, EMBASE and CINAHL for the period between 1976 and April 2018. We included randomized controlled trials comparing carbohydrate restriction with a control diet which aimed to maintain or increase carbohydrate intake, and that reported HbA_1c as an outcome and reported the amount of carbohydrate consumed during or at the end of the study, with outcomes reported at ≥3 months.

RESULTS

We identified 1402 randomized controlled trials, 25 of which met the inclusion criteria, incorporating 2132 participants for the main outcome. Definitions of low carbohydrate varied among the studies. The pooled effect estimate from meta-analysis was a weighted mean difference of -0.09% [95% CI -0.27, 0.08 (P = 0.30); I² 72% (P <0.001)], suggesting no effect on HbA_1c of restricting the quantity of carbohydrate. A subgroup analysis of diets containing 50-130 g carbohydrate resulted in a pooled effect estimate of -0.49% [95% CI -0.75, -0.23 (P <0.001); I² 0% (P = 0.56)], suggesting a clinically and statistically significant effect on HbA_1c in favour of low-carbohydrate diets in studies of ≤6 months' duration.

CONCLUSIONS

There was no overall pooled effect on HbA_1c in favour of restricting carbohydrate; however, restriction of carbohydrate to 50-130 g per day had beneficial effects on HbA_1c in trials up to 6 months. Future randomized controlled trials should be of >12 months' duration, assess pre-study carbohydrate intake, use recognized definitions of low-carbohydrate diets and examine reasons for non-adherence to prescribed diets in greater detail.

Three-Year Chronic Consumption of Low-Carbohydrate Diet Impairs Exercise Performance and Has a Small Unfavorable Effect on Lipid Profile in Middle-Aged Men

The objective of this research was to determine whether chronic (average 3.58 ± 1.56 years) deliberate adherence to low carbohydrate diets (LCDs) is associated with selected markers of metabolism, risk factors of cardiovascular disease (CVD), body mass and physical performance in apparently healthy middle-aged men (n = 12). The control group comprised age, body mass and height matched men using mixed diets (MDs). The diets used were registered for 7 days and analyzed in terms of the energy, carbohydrate, fat and protein contents. It was found that the diets used were isoenergetic, yet varied considerably in carbohydrate and fat content. The LCDs significantly intensified the ketogenesis process, increased resting blood total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and heart rate, (HR) and decreased respiratory exchange ratio (RER) in relation to MD subjects. An exercise trial revealed significant impairment of exercise in subjects following the LCDs. The results showed that in the case where the subjects of two investigated groups did not differ in their somatic variables, long-term adherence to the LCDs was associated with substantially reduced exercise performance in apparently healthy subjects, along with an association with a small unfavorable effect on their lipid profile.

Dietary Composition and Cardiovascular Risk: A Mediator or a Bystander?

The role of nutrition in the pathogenesis of cardiovascular disease has long been debated. The established notion of the deleterious effects of fat is recently under question, with numerous studies demonstrating the benefits of low-carbohydrate, high-fat diets in terms of obesity, diabetes, dyslipidemia, and metabolic derangement. Monounsaturated and polyunsaturated fatty acids, especially n-3 PUFAs (polyunsaturated fatty acids), are the types of fat that favor metabolic markers and are key components of the Mediterranean Diet, which is considered an ideal dietary pattern with great cardioprotective effects. Except for macronutrients, however, micronutrients like polyphenols, carotenoids, and vitamins act on molecular pathways that affect oxidative stress, endothelial function, and lipid and glucose homeostasis. In relation to these metabolic markers, the human gut microbiome is constantly revealed, with its composition being altered by even small dietary changes and different microbial populations being associated with adverse cardiovascular outcomes, thus becoming the target for potential new treatment interventions. This review aims to present the most recent data concerning different dietary patterns at both the macro- and micronutrient level and their association with atherosclerosis, obesity, and other risk factors for cardiovascular disease.

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.

A Randomized Controlled Trial of a Mini Low-Carbohydrate Diet and an Energy-Controlled Diet Among Japanese Patients With Type 2 Diabetes

Background

Low-carbohydrate diets have been shown to effectively improve the metabolic status of patients with type 2 diabetes mellitus. However, patients may find it challenging to maintain a strict low-carbohydrate diet. The objective of this study was to determine if a one-meal, low-carbohydrate diet is as effective in improving metabolic status as a conventional, energy-restricted diet among patients with type 2 diabetes mellitus.

Methods

In this 12-week randomized controlled study, the primary endpoint was differences in the changes of plasma glycosylated hemoglobin (HbA1c) levels between the two experimental groups. Since the two groups had differences in body weight, body mass index, and waist circumference, propensity score matching was used to assess HbA1c outcomes via cohort pairs according to age, sex, body weight, HbA1c level, and waist circumference.

Results

There were no differences in the changes in HbA1c between the two groups (P = 0.95). In addition, there were no differences in the changes in glycated albumin, 1,5-anhydroglucitol, lipid profile, body weight, waist circumference, and fat mass between the two groups. The mini low-carbohydrate diet group had an increased protein intake (P = 0.0085), as compared with the control group. However, neither group showed changes in their Diabetes Treatment Satisfaction Questionnaire score.

Conclusion

Either diet would be effective for improving the metabolic status of this study population.

A network meta-analysis on the comparative efficacy of different dietary approaches on glycaemic control in patients with type 2 diabetes mellitus

The aim of the present study is to assess the comparative efficacy of different dietary approaches on glycaemic control in patients with type 2 diabetes mellitus using a systematic review of the literature. Electronic and hand searches were performed until July 2017. The inclusion criteria were defined as follows: (1) randomized trial with a dietary approach; (2) adults with type 2 diabetes mellitus; (3) outcome either HbA1c (%) and/or fasting glucose (mmol/l); (4) minimum intervention period of 12 weeks. For each outcome measure, random effects network meta-analysis was performed in order to determine the pooled effect of each intervention relative to each of the other interventions. A total of 56 trials comparing nine dietary approaches (low-fat, Vegetarian, Mediterranean, high-protein, moderate-carbohydrate, low-carbohydrate, control, low GI/GL, Palaeolithic) enrolling 4937 participants were included. For reducing HbA1c, the low-carbohydrate diet was ranked as the best dietary approach (SUCRA: 84%), followed by the Mediterranean diet (80%) and Palaeolithic diet (76%) compared to a control diet. For reducing fasting glucose, the Mediterranean diet (88%) was ranked as the best approach, followed by Palaeolithic diet (71%) and Vegetarian diet (63%). The network analysis also revealed that all dietary approaches significantly reduce HbA1c (− 0.82 to − 0.47% reduction) and fasting glucose (− 1.61 to − 1.00 mmol/l reduction) compared to a control diet. According to the network meta-analysis the Mediterranean diet is the most effective and efficacious dietary approach to improve glycaemic control in type 2 diabetes patients.

Diet Behavior Change Techniques in Type 2 Diabetes: A Systematic Review and Meta-analysis

OBJECTIVE

Dietary behavior is closely connected to type 2 diabetes. The purpose of this meta-analysis was to identify behavior change techniques (BCTs) and specific components of dietary interventions for patients with type 2 diabetes associated with changes in HbA_1c and body weight.

RESEARCH DESIGN AND METHODS

The Cochrane Library, CINAHL, Embase, PubMed, PsycINFO, and Scopus databases were searched. Reports of randomized controlled trials published during 1975-2017 that focused on changing dietary behavior were selected, and methodological rigor, use of BCTs, and fidelity and intervention features were evaluated.

RESULTS

In total, 54 studies were included, with 42 different BCTs applied and an average of 7 BCTs used per study. Four BCTs-"problem solving," "feedback on behavior," "adding objects to the environment," and "social comparison"-and the intervention feature "use of theory" were associated with >0.3% (3.3 mmol/mol) reduction in HbA_1c. Meta-analysis revealed that studies that aimed to control or change the environment showed a greater reduction in HbA_1c of 0.5% (5.5 mmol/mol) (95% CI -0.65, -0.34), compared with 0.32% (3.5 mmol/mol) (95% CI -0.40, -0.23) for studies that aimed to change behavior. Limitations of our study were the heterogeneity of dietary interventions and poor quality of reporting of BCTs.

CONCLUSIONS

This study provides evidence that changing the dietary environment may have more of an effect on HbA_1c in adults with type 2 diabetes than changing dietary behavior. Diet interventions achieved clinically significant reductions in HbA_1c, although initial reductions in body weight diminished over time. If appropriate BCTs and theory are applied, dietary interventions may result in better glucose control.

Carbohydrate-Restriction with High-Intensity Interval Training: An Optimal Combination for Treating Metabolic Diseases?

Lifestyle interventions incorporating both diet and exercise strategies remain cornerstone therapies for treating metabolic disease. Carbohydrate-restriction and high-intensity interval training (HIIT) have independently been shown to improve cardiovascular and metabolic health. Carbohydrate-restriction reduces postprandial hyperglycemia, thereby limiting potential deleterious metabolic and cardiovascular consequences of excessive glucose excursions. Additionally, carbohydrate-restriction has been shown to improve body composition and blood lipids. The benefits of exercise for improving insulin sensitivity are well known. In this regard, HIIT has been shown to rapidly improve glucose control, endothelial function, and cardiorespiratory fitness. Here, we report the available evidence for each strategy and speculate that the combination of carbohydrate-restriction and HIIT will synergistically maximize the benefits of both approaches. We hypothesize that this lifestyle strategy represents an optimal intervention to treat metabolic disease; however, further research is warranted in order to harness the potential benefits of carbohydrate-restriction and HIIT for improving cardiometabolic health.

Evidence that supports the prescription of low-carbohydrate high-fat diets: a narrative review

Low-carbohydrate high-fat (LCHF) diets are a highly contentious current topic in nutrition. This narrative review aims to provide clinicians with a broad overview of the effects of LCHF diets on body weight, glycaemic control and cardiovascular risk factors while addressing some common concerns and misconceptions. Blood total cholesterol and LDL-cholesterol concentrations show a variable, highly individual response to LCHF diets, and should be monitored in patients adhering to this diet. In contrast, available evidence from clinical and preclinical studies indicates that LCHF diets consistently improve all other markers of cardiovascular risk-lowering elevated blood glucose, insulin, triglyceride, ApoB and saturated fat (especially palmitoleic acid) concentrations, reducing small dense LDL particle numbers, glycated haemoglobin (HbA_1c) levels, blood pressure and body weight while increasing low HDL-cholesterol concentrations and reversing non-alcoholic fatty liver disease (NAFLD). This particular combination of favourable modifications to all these risk factors is a benefit unique to LCHF diets. These effects are likely due in part to reduced hunger and decreased ad libitum calorie intake common to low-carbohydrate diets, allied to a reduction in hyperinsulinaemia, and reversal of NAFLD. Although LCHF diets may not be suitable for everyone, available evidence shows this eating plan to be a safe and efficacious dietary option to be considered. LCHF diets may also be particularly beneficial in patients with atherogenic dyslipidaemia, insulin resistance, and the frequently associated NAFLD.

An Online Intervention Comparing a Very Low-Carbohydrate Ketogenic Diet and Lifestyle Recommendations Versus a Plate Method Diet in Overweight Individuals With Type 2 Diabetes: A Randomized Controlled Trial

Background

Type 2 diabetes is a prevalent, chronic disease for which diet is an integral aspect of treatment. In our previous trial, we found that recommendations to follow a very low-carbohydrate ketogenic diet and to change lifestyle factors (physical activity, sleep, positive affect, mindfulness) helped overweight people with type 2 diabetes or prediabetes improve glycemic control and lose weight. This was an in-person intervention, which could be a barrier for people without the time, flexibility, transportation, social support, and/or financial resources to attend.

Objective

The aim was to determine whether an online intervention based on our previous recommendations (an ad libitum very low-carbohydrate ketogenic diet with lifestyle factors; “intervention”) or an online diet program based on the American Diabetes Associations’ “Create Your Plate” diet (“control”) would improve glycemic control and other health outcomes among overweight individuals with type 2 diabetes.

Methods

In this pilot feasibility study, we randomized overweight adults (body mass index ≥25) with type 2 diabetes (glycated hemoglobin [HbA_1c] 6.5%-9.0%) to a 32-week online intervention based on our previous recommendations (n=12) or an online diet program based around a plate method diet (n=13) to assess the impact of each intervention on glycemic control and other health outcomes. Primary and secondary outcomes were analyzed by mixed-effects linear regression to compare outcomes by group.

Results

At 32 weeks, participants in the intervention group reduced their HbA_1c levels more (estimated marginal mean [EMM] –0.8%, 95% CI –1.1% to –0.6%) than participants in the control group (EMM –0.3%, 95% CI –0.6% to 0.0%; P=.002). More than half of the participants in the intervention group (6/11, 55%) lowered their HbA_1c to less than 6.5% versus 0% (0/8) in the control group (P=.02). Participants in the intervention group lost more weight (EMM –12.7 kg, 95% CI –16.1 to –9.2 kg) than participants in the control group (EMM –3.0 kg, 95% CI –7.3 to 1.3 kg; P<.001). A greater percentage of participants lost at least 5% of their body weight in the intervention (10/11, 90%) versus the control group (2/8, 29%; P=.01). Participants in the intervention group lowered their triglyceride levels (EMM –60.1 mg/dL, 95% CI –91.3 to –28.9 mg/dL) more than participants in the control group (EMM –6.2 mg/dL, 95% CI –46.0 to 33.6 mg/dL; P=.01). Dropout was 8% (1/12) and 46% (6/13) for the intervention and control groups, respectively (P=.07).

Conclusions

Individuals with type 2 diabetes improved their glycemic control and lost more weight after being randomized to a very low-carbohydrate ketogenic diet and lifestyle online program rather than a conventional, low-fat diabetes diet online program. Thus, the online delivery of these very low-carbohydrate ketogenic diet and lifestyle recommendations may allow them to have a wider reach in the successful self-management of type 2 diabetes.

Trial Registration

ClinicalTrials.gov NCT01967992; https://clinicaltrials.gov/ct2/show/NCT01967992 (Archived by WebCite at http://www.webcitation.org/6o0fI9Mkq)

Dietary Intake and Cardiovascular Risk Factors in Icelanders Following Voluntarily a Low Carbohydrate Diet

Background/Aim

Most studies regarding low-carbohydrate diets (LCDs) have been intervention studies. The aim of the current study was to investigate dietary intake and cardiovascular risk factors among individuals who voluntarily follow a LCD.

Methods

A cross-sectional study was conducted (N = 54, 20–66yrs) in Reykjavik, Iceland. Participants recorded food intake for three days. Blood samples were analyzed for cardiovascular risk factors.

Results

Nearly half of the participants were obese and around 60% had been on a LCD for ≥ 6 months. Fifty percent claimed they had lost weight during the past month. The median intake of carbohydrate, protein and fat were 8%, 22% and 68% E (hereof 25% saturated fatty acids), respectively. The consumption of bread and wholegrain cereals was very low (<5g/day), including the intake of dietary fiber (11g/day). Median fruit intake was 12 g/day. Intake of red meat and meat products was double that of the general population or ~900 g/week. Median intake of vitamins and minerals were mostly higher than the estimated average requirements. Cardiovascular risk factors were mostly within normal range. Mean blood lipids were slightly elevated although the high density lipoprotein/total cholesterol ratio was normal.

Conclusion

Despite poor diet quality and high prevalence of obesity, individuals who voluntarily follow a LCD have cardiovascular risk factors mostly within reference range. These individuals consume very low amounts of carbohydrates and high amounts of fat and saturated fat acids. Intake of red meat and processed meat exceeds recommended intake. Very low intake of whole grain cereals and fruits results in low intake of fiber. Long term health implications need to be examined further in longitudinal studies.

The Effects of Low-Carbohydrate Diets on Psychosocial Outcomes in Obesity/Overweight: A Systematic Review of Randomized, Controlled Studies

Background: Little is known about the relative psychosocial effects of carbohydrate reduction in comparison to other weight-loss diets in subjects receiving treatment for obesity/overweight. We, therefore, set out to conduct a systematic review of the psychosocial outcomes of such patients, treated by means of either a low-carbohydrate diet or an isocaloric diet of other macronutrient composition. Methods: Literature searches, study selection, method development, and quality appraisal were performed independently by two authors, and data were synthesized using a narrative approach, in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines. Results: Eight randomized controlled studies met the inclusion criteria, and their subsequent analysis revealed that improvements in psychological and social outcomes do occur during short- and long-term weight loss programmes, but that low-carbohydrate diets have no greater effect on psychosocial outcomes when compared to diets of different macronutrient composition at either short- or long-term follow-up (one-year). However, the lack of studies with longer duration follow-up, and the absence of data in the adolescent population limit the generalizability of our findings. Conclusion: The short- and long-term improvements in psychosocial outcomes seen in patients undergoing weight-loss treatment appear to be independent of the macronutrient composition of their diet.

Insulin, carbohydrate restriction, metabolic syndrome and cancer

We propose that dietary carbohydrate restriction, particularly ketogenic diets, may provide benefit as a therapeutic or preventive strategy in cancer, alone or as an adjunct to pharmacology. The argument derives from several points of evidence: There is a close association between cancer and both diabetes and obesity. Extensive evidence shows that low carbohydrate diets are the most effective dietary treatment of Type 2 diabetes and dietary adjunct in Type 1. Such diets also target all the markers of metabolic syndrome. Finally, de facto reduction in carbohydrate likely contributes to total dietary restriction, which is effective in the prevention and treatment of cancer. The idea is consistent with recent interest in treating cancer with drugs that target diabetes. To move forward, we must understand obesity and diabetes as response to a hyperglycemic state rather than simply a cause of downstream effects.

Dietary carbohydrate restriction as the first approach in diabetes management: critical review and evidence base

The inability of current recommendations to control the epidemic of diabetes, the specific failure of the prevailing low-fat diets to improve obesity, cardiovascular risk, or general health and the persistent reports of some serious side effects of commonly prescribed diabetic medications, in combination with the continued success of low-carbohydrate diets in the treatment of diabetes and metabolic syndrome without significant side effects, point to the need for a reappraisal of dietary guidelines. The benefits of carbohydrate restriction in diabetes are immediate and well documented. Concerns about the efficacy and safety are long term and conjectural rather than data driven. Dietary carbohydrate restriction reliably reduces high blood glucose, does not require weight loss (although is still best for weight loss), and leads to the reduction or elimination of medication. It has never shown side effects comparable with those seen in many drugs. Here we present 12 points of evidence supporting the use of low-carbohydrate diets as the first approach to treating type 2 diabetes and as the most effective adjunct to pharmacology in type 1. They represent the best-documented, least controversial results. The insistence on long-term randomized controlled trials as the only kind of data that will be accepted is without precedent in science. The seriousness of diabetes requires that we evaluate all of the evidence that is available. The 12 points are sufficiently compelling that we feel that the burden of proof rests with those who are opposed.