Effects of a Low-Carbohydrate Dietary Intervention on Hemoglobin A1c: A Randomized Clinical Trial

The effects of low-carbohydrate diet on glucose and lipid metabolism in overweight or obese patients with T2DM: a meta-analysis of randomized controlled trials

Background

The dual burden of Type 2 Diabetes Mellitus (T2DM) and obesity is a critical public health issue. Low-carbohydrate diets have emerged as a potential intervention, yet clinical evidence remains inconclusive.

Purpose

This meta-analysis assesses the impact of low-carbohydrate diets on metabolic profiles in overweight or obese T2DM patients, aiming to guide clinical practice.

Methods

A systematic review identified randomized clinical trials (RCTs) comparing low-carbohydrate diets to control diets in T2DM patients from PubMed, Embase, and the Cochrane Library databases up to April 2023.

Results

Seventeen RCTs, encompassing 1,197 participants, demonstrated that low-carbohydrate diets significantly improved HbA1c levels and fasting plasma glucose (mean difference [MD] = -0.36, 95% CI -0.44 to -0.29, p < 0.00001; MD = -10.71, 95% CI -14.39 to -7.03, p < 0.00001). They also reduced triglycerides and increased HDL cholesterol (MD = -19.91, 95% CI -28.83 to -10.99, p < 0.00001; MD = 2.49, 95% CI 1.07-3.91, p = 0.0006), without affecting LDL and total cholesterol. Weight loss, reduced BMI, lower diastolic blood pressure, and decreased waist circumference were additional benefits.

Conclusion

Low-carbohydrate diets may enhance glycemic control and lipid profiles in overweight or obese T2DM patients, warranting consideration in T2DM management. However, the variability in diet definitions and methodologies underscores the necessity for further research to standardize dietary guidelines and evaluate long-term effects.

Efficacy of Low-Carbohydrate Diets Versus Low-Fat Diets in Glycemic Control Among Patients With Type 2 Diabetes: A Systematic Review

This systematic review evaluates the comparative efficacy of low-carbohydrate diets (LCDs) versus low-fat diets (LFDs) in improving glycemic control, weight management, and lipid profiles in individuals with type 2 diabetes mellitus (T2DM) or prediabetes. Seven randomized controlled trials involving diverse populations were included, with dietary interventions ranging from very low-carbohydrate ketogenic (LCK) diets (typically <10% of total caloric intake from carbohydrates, with higher fat and moderate protein) to moderate carbohydrate regimens (30-45% of total calories). LFDs, in contrast, prioritized carbohydrate intake (50-60% of total calories), with reduced fat (<20-30%) and moderate protein (15-20%). Across studies, LCDs consistently demonstrated greater reductions in HbA1c, fasting glucose, and triglycerides, alongside superior weight loss and increased high-density lipoprotein cholesterol compared to LFDs. Additionally, LCDs were associated with significant reductions in diabetes medication use, highlighting their potential to decrease pharmacological dependency and improve metabolic outcomes, including enhanced insulin sensitivity and reduced inflammation. Despite variability in long-term outcomes and adherence, LCDs emerged as a promising alternative to traditional dietary approaches for managing T2DM. Further research is warranted to explore strategies to improve dietary adherence, such as behavioral interventions and technological support, and to evaluate long-term sustainability, including their effects on cardiovascular health and quality of life. These findings underscore the transformative potential of LCDs in diabetes management and highlight the need for personalized dietary approaches.

Asian Low-Carbohydrate Diet with Increased Whole Egg Consumption Improves Metabolic Outcomes in Metabolic Syndrome: A 52-Week Intervention Study

BACKGROUND

The low-carbohydrate-ketogenic diet, an effective strategy to address metabolic syndrome (MetS) and obesity has raised concerns about high-fat consumption on atherogenic lipoproteins.

OBJECTIVE

The aim of this study was to compare the Asian ketogenic diet (AKD), which incorporates balanced protein and fat intake from Asian foods, with a balanced low-caloric diet (BLC) in individuals diagnosed with MetS.

METHODS

A 52-wk randomized clinical trial included 3 parallel groups: AKD with increased whole egg intake [egg yolk Asian ketogenic diet (Yolk-AKD, n = 28)], yolk-free ketogenic diet with egg white supplementation [egg white Asian ketogenic diet (White-AKD, n = 26)], and BLC (n = 22). Primary outcomes were anthropometric and metabolic changes.

RESULTS

The AKD groups achieved significant reductions in weight and waist circumference (P < 0.05). Compared with the BLC group, the AKD groups demonstrated significant improvements in insulin resistance at week 6 and in triglyceride concentrations at weeks 12 (Yolk-AKD) and 35 (White-AKD) (P < 0.05). The AKD groups experienced improvements in hormones associated with insulin sensitivity and appetite, whereas only the Yolk-AKD group had a significant decrease in inflammation-related hormones (P < 0.05). From weeks 35-52, the AKD maintained reductions in anthropometric measurements, blood pressure, improved glucose tolerance, enhanced lipid profiles, and better liver function compared with the BLC.

CONCLUSIONS

The AKD proved safe and effective, yielding various metabolic improvements in individuals with MetS compared with the BLC. Emphasizing a low-saturated fat diet while disregarding dietary cholesterol, this approach holds promise for MetS and obesity management. The inclusion of both White-AKD and Yolk-AKD groups allowed for a comprehensive assessment of the AKD's impact, elucidating the differential effects of whole egg consumption on metabolic outcomes. Further studies are warranted. This trial was registered at clinicaltrials.gov as NCT04608136.

Feasibility of the MIND+SOUL Culturally Tailored Brain Healthy Diet: A Pilot Study

Alzheimer's disease (AD) disproportionately impacts Black Americans, who are three times more likely to develop AD. While heart-healthy diets have shown potential in reducing AD risk, research on adapted dietary interventions for Black American communities remains limited. This pilot study assessed the feasibility and acceptability of an adapted brain healthy diet intervention (MIND + SOUL) and explored changes in cardiometabolic risk and cognition. Twenty-nine participants completed the 12-week intervention, which included culturally tailored health education, cooking classes, health coaching, and groceries. Feasibility was assessed by attendance and retention rates, while acceptability was measured by two questionnaires. Participants had a mean age of 70.3, with 10.3% male. The intervention demonstrated high feasibility (89.3% retention) and acceptability (mean = 71.9, SD = 8.59), with meaningful improvements in body mass index (estimate = -0.54, P = 0.009), dietary intake (estimate = 28.39, P = 0.042), and executive function (estimate = 3.32, P < 0.001). However, no significant changes in blood-based biomarkers were observed. The MIND + SOUL intervention demonstrated high feasibility and acceptability, improvements in body composition, cognitive function, and dietary behaviors, despite no significant changes in blood-based biomarkers. Findings suggest potential benefits for reducing AD risk factors and promoting healthy aging. Clinical Trials Registry: ClinicalTrials.Gov; NCT05414682.

Low-Carbohydrate Dietary Interventions for Metabolic Control in Individuals With Type 2 Diabetes Mellitus: An Overview of Systematic Reviews

CONTEXT

Dietary interventions providing different amounts of carbohydrates have been proposed as a means of achieving glycemic control and weight loss in type 2 diabetes mellitus (T2DM); however, the supporting evidence is heterogeneous, making this recommendation difficult to apply in nutritional clinical practice.

OBJECTIVE

The aim was to assess the quality of evidence from meta-analyses on low-carbohydrate (LC) dietary interventions for glycemic control, weight loss, and lipid profile in individuals with T2DM.

DATA SOURCES

The MEDLINE, Web of Science, and Scopus databases were searched until September 2023.

DATA EXTRACTION

A systematic review was conducted. Systematic reviews with meta-analysis of randomized clinical trials designed to assess glycated hemoglobin (HbA1c) reductions in individuals with T2DM were eligible. The AMSTAR-2 critical appraisal tool was used to evaluate the methodological aspects of all included studies. The GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) approach was used to assess the certainty of the evidence.

DATA ANALYSIS

The LC interventions were associated with a reduction in HbA1c (%) of -0.42 (-1.45 to -0.09; high certainty of evidence) without considering follow-up time; at up to 3 months of follow-up of -0.28 (-0.13 to -0.43); at up to 6 months of follow-up of -0.40 (-0.61 to -0.09); at 6 to 12 months of follow-up of -0.32 (-0.49 to 0.11); and at >12 months of follow-up time of -0.31 (-0.14 to -0.65) compared with control diets.

CONCLUSION

LC diets can help reduce HbA1c in individuals with T2DM in the short term (up to 3 months). However, dietary recommendations must always be individualized, as the studies reviewed herein analyzed different populations and used different definitions of what constitutes an LC diet.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO no. CRD42023404197.

Nutrient analysis of three low-carbohydrate diets differing in carbohydrate content

Introduction

Low-carbohydrate diets are increasing in popularity. Despite clinical evidence demonstrating their safety and efficacy, concerns regarding the nutrient adequacy of low-carbohydrate diets persist. The aims of this study were to assess the nutrient adequacy of three 7-day meal plans that delivered 20 (VLCD20), 40 (VLCD40), and 100 (LCD100) grams of net carbohydrate per day respectively.

Methods

Nutrient analyses were conducted using USDA Food Data Central.

Results

All three low-carbohydrate meal plans exceeded recommendations for vitamins A, C, D, E, K, thiamin, riboflavin, niacin, B6, folate and B12 in males and females 31-70 years and exceeded calcium recommendations for adults 31-50 years but remained below the Tolerable Upper Intake Level. VLCD40 and LCD100 met or exceeded fiber recommendations for females ages 31-70 years and were adequate for males 51-70 years. None of the meal plans contributed meaningful amounts of added sugar. The plans exceeded the Recommended Dietary Allowance for protein for adults ages 31-70 years of age but were within the Acceptable Macronutrient Distribution Range of 10-35% of energy. The plans slightly exceeded recommendations for saturated fat and sodium but were lower in these nutrients than the average American diet and had more favorable omega-6 to omega-3 and sodium to potassium ratios than is typical. All three meals plans met or exceeded the Estimated Average Requirement for micronutrients in females ages 31-50 years, the population group most likely to consume low-carbohydrate diets.

Discussion

Well-constructed low-carbohydrate meal plans can be nutritionally adequate in adults.

Rationale and design of the KP ENRICH trial: A food is medicine intervention in low-income high-risk adults with diabetes within Kaiser Permanente

BACKGROUND

Food insecurity is associated with poor glycemic control and increased risk for diabetes-related complications. The clinical benefit of addressing these challenges through a medically supportive grocery prescription (GRx) program in patients with type 2 diabetes mellitus (T2D) remains unclear. We report the aims and design of a randomized clinical trial to evaluate the effectiveness of a 6-month GRx intervention on hemoglobin A1c (HbA1c) levels among low-income adults with T2D.

METHODS

The Kaiser Permanente Evaluating Nutritional Interventions in Food-Insecure High-Risk Adults (KP ENRICH) Study is a pragmatic randomized trial enrolling 1100 participants within Kaiser Permanente Northern California and Southern California, two integrated health care delivery systems serving >9 million members. Medicaid-insured adults with T2D and baseline HbA1c ≥7.5% will be randomized at a 1:1 ratio to either GRx, delivered as $100 per month for select items from among a curated list of healthful food groups in an online grocery ordering and home-delivery platform along with biweekly digital nutrition educational materials, or control, consisting of free membership and deliveries from the online grocery platform but without curated food groups or purchasing dollars. The primary outcome is 6-month change in HbA1c. Secondary outcomes include 12-month change in HbA1c, and 6- and 12-month change in medical resource utilization, food security, nutrition security, dietary habits, diabetes-related quality of life, and dietary self-efficacy.

CONCLUSIONS

The results of this large randomized clinical trial of GRx will help inform future policy and health system-based initiatives to improve food and nutrition security, disease management, and health equity among patients with T2D.

Prospective cohort studies underscore the association of abnormal glycemic measures with all-cause and cause-specific mortalities

The role of fasting plasma glucose (FPG), glycated hemoglobin (HbA1c), and triglyceride-glucose index (TyG index) in predicting all-cause and cause-specific mortalities remains elusive. This study included 384,420 adults from the Shanghai cohort and the UK Biobank (UKB) cohort. After multivariable adjustment in the Cox models, FPG ≥7.0 mmol/L or HbA1c ≥ 6.5% increased the risk of all-cause mortality, FPG ≥5.6 mmol/L or HbA1c ≥ 6.5% increased CVD-related mortality, and higher or lower TyG index increased all-cause and CVD-related mortalities in the Shanghai cohort; FPG ≥5.6 mmol/L, HbA1c ≥ 5.7%, TyG index <8.31 or ≥9.08 increased the risks of all-cause, CVD-related, and cancer-related mortalities in the UKB cohort. FPG or HbA1c increased the discrimination of the conventional risk model in predicting all-cause and CVD-related mortalities in both cohorts. Thus, increased levels of FPG and HbA1c and U-shaped TyG index increase the risks of all-cause especially CVD-related mortalities.

Improved Gut Health May Be a Potential Therapeutic Approach for Managing Prediabetes: A Literature Review

Given the growing global threat and rising prevalence of type 2 diabetes mellitus (T2DM), addressing this metabolic disease is imperative. T2DM is preceded by prediabetes (PD), an intermediate hyperglycaemia that goes unnoticed for years in patients. Several studies have shown that gut microbial diversity and glucose homeostasis in PD or T2DM patients are affected. Therefore, this review aims to synthesize the existing literature to elucidate the association between high-calorie diets, intestinal permeability and their correlation with PD or T2DM. Moreover, it discusses the beneficial effects of different dietary interventions on improving gut health and glucose metabolism. The primary factor contributing to complications seen in PD or T2DM patients is the chronic consumption of high-calorie diets, which alters the gut microbial composition and increases the translocation of toxic substances from the intestinal lumen into the bloodstream. This causes an increase in inflammatory response that further impairs glucose regulation. Several dietary approaches or interventions have been implemented. However, only a few are currently in use and have shown promising results in improving beneficial microbiomes and glucose metabolism. Therefore, additional well-designed studies are still necessary to thoroughly investigate whether improving gut health using other types of dietary interventions can potentially manage or reverse PD, thereby preventing the onset of T2DM.

Association of low carbohydrate diet score with the risk of type 2 diabetes in an Australian population: A longitudinal study

AIMS

We aimed to assess the association of a low carbohydrate diet score (LCD) with the incidence of type 2 diabetes (T2D) using Melbourne Collaborative Cohort Study (MCCS) data.

METHODS

Between 1990 and 1994, the MCCS recruited 41,513 people aged 40-69 years. The first and second follow-ups were conducted in 1995-1998 and 2003-2007, respectively. We analyzed data from 39,185 participants. LCD score was calculated at baseline as the percentage of energy from carbohydrate, fat, and protein. The higher the score the less percentage of carbohydrates contributed to energy intake. The association of LCD quintiles with the incidence of diabetes was assessed using modified Poisson regression, adjusted for lifestyle, obesity, socioeconomic and other confounders. Mediation of the association by adiposity (BMI) was assessed.

RESULTS

LCD was positively associated with diabetes risk. Higher LCD score (p for trend = 0.001) was associated with increased risk of T2D. Quintile 5 (38 % energy from carbohydrates) versus quintile 1 (55 % energy from carbohydrates) showed a 20 % increased diabetes risk (incidence risk ratio (IRR) = 1.20 (95 % CI: 1.05-1.37)). A further adjustment for BMI (Body Mass Index) and WHR (Waist-to-Hip-Ratio) eliminated the association. Mediation analysis demonstrated that BMI mediated 76 % of the LCD & diabetes association.

CONCLUSIONS

Consuming a low carbohydrate diet, reflected as a high LCD score, may increase the risk of T2D which is largely explained by obesity. Results highlight the need for further studies, including clinical trials investigating the effects of a low carbohydrate diet in T2D.

Low-carbohydrate diet for people with type 2 diabetes mellitus

OBJECTIVES

This is a protocol for a Cochrane Review (intervention). The objectives are as follows: To assess the effects of a low-carbohydrate diet in adults with type 2 diabetes mellitus.

Do Precision and Personalised Nutrition Interventions Improve Risk Factors in Adults with Prediabetes or Metabolic Syndrome? A Systematic Review of Randomised Controlled Trials

This review aimed to synthesise existing literature on the efficacy of personalised or precision nutrition (PPN) interventions, including medical nutrition therapy (MNT), in improving outcomes related to glycaemic control (HbA1c, post-prandial glucose [PPG], and fasting blood glucose), anthropometry (weight, BMI, and waist circumference [WC]), blood lipids, blood pressure (BP), and dietary intake among adults with prediabetes or metabolic syndrome (MetS). Six databases were systematically searched (Scopus, Medline, Embase, CINAHL, PsycINFO, and Cochrane) for randomised controlled trials (RCTs) published from January 2000 to 16 April 2023. The Academy of Nutrition and Dietetics Quality Criteria were used to assess the risk of bias. Seven RCTs (n = 873), comprising five PPN and two MNT interventions, lasting 3-24 months were included. Consistent and significant improvements favouring PPN and MNT interventions were reported across studies that examined outcomes like HbA1c, PPG, and waist circumference. Results for other measures, including fasting blood glucose, HOMA-IR, blood lipids, BP, and diet, were inconsistent. Longer, more frequent interventions yielded greater improvements, especially for HbA1c and WC. However, more research in studies with larger sample sizes and standardised PPN definitions is needed. Future studies should also investigate combining MNT with contemporary PPN factors, including genetic, epigenetic, metabolomic, and metagenomic data.

Diet and Meal Pattern Determinants of Glucose Levels and Variability in Adults with and without Prediabetes or Early-Onset Type 2 Diabetes: A Pilot Study

This observational pilot study examined the association between diet, meal pattern and glucose over a 2-week period under free-living conditions in 26 adults with dysglycemia (D-GLYC) and 14 with normoglycemia (N-GLYC). We hypothesized that a prolonged eating window and late eating occasions (EOs), along with a higher dietary carbohydrate intake, would result in higher glucose levels and glucose variability (GV). General linear models were run with meal timing with time-stamped photographs in real time, and diet composition by dietary recalls, and their variability (SD), as predictors and glucose variables (mean glucose, mean amplitude of glucose excursions [MAGE], largest amplitude of glucose excursions [LAGE] and GV) as dependent variables. After adjusting for calories and nutrients, a later eating midpoint predicted a lower GV (β = -2.3, SE = 1.0, p = 0.03) in D-GLYC, while a later last EO predicted a higher GV (β = 1.5, SE = 0.6, p = 0.04) in N-GLYC. A higher carbohydrate intake predicted a higher MAGE (β = 0.9, SE = 0.4, p = 0.02) and GV (β = 0.4, SE = 0.2, p = 0.04) in N-GLYC, but not D-GLYC. In summary, our data suggest that meal patterns interact with dietary composition and should be evaluated as potential modifiable determinants of glucose in adults with and without dysglycemia. Future research should evaluate causality with controlled diets.

Joint associations among non-essential heavy metal mixtures and nutritional factors on glucose metabolism indexes in US adults: evidence from the NHANES 2011-2016

Dietary intake can modify the impact of metals on human health, and is also closely related to glucose metabolism in human bodies. However, research on their interaction is limited. We used data based on 1738 adults aged ≥20 years from the National Health and Nutrition Examination Survey 2011-2016. We combined linear regression and restricted cubic splines with Bayesian kernel machine regression (BKMR) to identify metals associated with each glucose metabolism index (P < 0.05 and the posterior inclusion probabilities of BKMR >0.5) in eight non-essential heavy metals (barium, cadmium, antimony, tungsten, uranium, arsenic, lead, and thallium) and glucose metabolism indexes [fasting plasma glucose (FPG), blood hemoglobin A1c (HbA1c) and homeostatic model assessment of insulin resistance (HOMA-IR)]. We identified two pairs of metals associated with glucose metabolism indexes: cadmium and tungsten to HbA1c and barium and thallium to HOMA-IR. Then, the cross-validated kernel ensemble (CVEK) approach was applied to identify the specific nutrient group (nutrients) that interacted with the association. By using the CVEK model, we identified significant interactions between the energy-adjusted diet inflammatory index (E-DII) and cadmium, tungsten and barium (all P < 0.05); macro-nutrients and cadmium, tungsten and barium (all P < 0.05); minerals and cadmium, tungsten, barium and thallium (all P < 0.05); and A vitamins and thallium (P = 0.043). Furthermore, a lower E-DII, a lower intake of carbohydrates and phosphorus, and a higher consumption of magnesium seem to attenuate the positive association between metals and glucose metabolism indexes. Our finding identifying the nutrients that interact with non-essential heavy metals could provide a feasible nutritional guideline for the general population to protect against the adverse effects of non-essential heavy metals on glucose metabolism.

Unraveling the link between dietary factors and cardiovascular metabolic diseases: Insights from a two-sample Mendelian Randomization investigation

BACKGROUND

When specific nutrients are inadequate, vulnerability to cardiovascular and metabolic illnesses increases. The data linking dietary nutrition with these illnesses, however, has been sparse in the past observational research and randomized controlled trials.

OBJECTIVES

A Mendelian randomization (MR) analysis was performed to assess the influence of macronutrients (fat, protein, sugar, and carbohydrates) and micronutrients (β-carotene, folate, calcium, iron, copper, magnesium, phosphorus, selenium, zinc, vitamin C, vitamin D, vitamin B, and vitamin B12) on the susceptibility to cardiovascular metabolic disorders, including coronary artery disease, heart failure, ischemic stroke, and type 2 diabetes.

METHODS

We employed a two-sample Mendelian randomization (MR) analysis, utilizing inverse variance weighting and conducting comprehensive sensitivity assessments. We obtained publicly accessible summary data from separate cohorts comprising individuals of European ancestry. The level of statistical significance was established at a threshold of P < 0. 00074.

RESULTS

Based on our research findings, we have established a causal association between the consumption of circulating fat and the development of cardiovascular and metabolic diseases. The study found that an increase of one standard deviation in fat consumption was associated with a decreased risk of heart failure, with an odds ratio of 0. 56 (95 % CI: 0. 40-0. 79; p = 0. 0007). Notably, various sensitivity analyses confirmed the robustness of this association. Conversely, we did not find any significant correlation between other dietary components and the risk of cardiovascular and metabolic disorders.

CONCLUSION

Our research findings demonstrate a conspicuous impact of dietary fat consumption on the susceptibility to heart failure, independent of coronary artery disease, diabetes, and stroke. Consequently, it is indicated that dietary factors are unrelated to the predisposition to cardiovascular metabolic disorders.

Individualized Nutritional Management Using Dishcook Improves Nutrition Status Markers in Patients with Intellectual Disability

Dishcook is a new cooking system that allows individual cooking using a dedicated induction heater. This study investigated whether Dishcook use affects the nutritional value of individuals with intellectual disabilities. This study was conducted on users receiving support from a continuous-employment office in Obama City, Fukui Prefecture, in 2022. Of these participants, 18 (seven women and 11 men) who requested the use of the Dishcook were included in the analysis. The study period was from January to August 2023. The mean age was 48.72±16.24 y. A significant increase in the overall phase angles of the limbs was observed. Triglyceride, LDL cholesterol, HbA1c, and serum zinc levels improved in patients who used the Dishcook. The phase angle obtained using Bioelectrical Impedance Analysis also improved, indicating the usefulness of the Dishcook in treating metabolic diseases and the possibility of individualized nutritional management.

Effectiveness of Technology-Enabled, Low Carbohydrate Dietary Interventions, in the Prevention or Treatment of Type 2 Diabetes Mellitus in Adults: A Systematic Literature Review of Randomised Controlled and Non-Randomised Trials

Evidence suggests that low carbohydrate dietary (LCD) approaches can improve glycaemic control and may result in type 2 diabetes mellitus (T2DM) remission. This systematic literature review (SLR) aimed to assess the effectiveness of technology-enabled LCD interventions in the management of people with prediabetes or T2DM. Data sources included Medline, Embase, CINAHL, and Web of Science. Randomised (RCTs) or non-randomised (non-RCTs) controlled trials investigating the effect of technology-enabled LCDs (<130 g/day) or very low carbohydrate diets (VLCDs < 50 g/day) on glycosylated haemoglobin A1c (HbA1c) for at least three months and published in English between 2009 and 2023 were included. Risk of bias assessment, data extraction, and synthesis were conducted using standard tools and procedures. Six studies (two RCTs and four non-RCTs, total sample, n = 1519) were identified and included in the SLR. Two studies examining LCDs reported significant reductions in mean HbA1c (0.4% and -1.2%) and weight loss (-3.8 kg and -7.5 kg) at one year. Three studies examining VLCDs reported significant reductions in mean HbA1c (-0.8% to -1.3%) and weight loss (-12 kg to -14 kg) up to two years. Technology-enabled LCD or VLCD interventions can be a novel approach in helping people with prediabetes or T2DM self-manage their condition and possibly achieve remission. However, further research is required to determine the sustainability, effectiveness, and safety of this approach.

Low carbohydrate high fat ketogenic diets on the exercise crossover point and glucose homeostasis

In exercise science, the crossover effect denotes that fat oxidation is the primary fuel at rest and during low-intensity exercise with a shift towards an increased reliance on carbohydrate oxidation at moderate to high exercise intensities. This model makes four predictions: First, >50% of energy comes from carbohydrate oxidation at ≥60% of maximum oxygen consumption (VO2max), termed the crossover point. Second, each individual has a maximum fat oxidation capacity (FATMAX) at an exercise intensity lower than the crossover point. FATMAX values are typically 0.3-0.6 g/min. Third, fat oxidation is minimized during exercise ≥85%VO2max, making carbohydrates the predominant energetic substrate during high-intensity exercise, especially at >85%VO2max. Fourth, high-carbohydrate low-fat (HCLF) diets will produce superior exercise performances via maximizing pre-exercise storage of this predominant exercise substrate. In a series of recent publications evaluating the metabolic and performance effects of low-carbohydrate high-fat (LCHF/ketogenic) diet adaptations during exercise of different intensities, we provide findings that challenge this model and these four predictions. First, we show that adaptation to the LCHF diet shifts the crossover point to a higher %VO2max (>80%VO2max) than previously reported. Second, substantially higher FATMAX values (>1.5 g/min) can be measured in athletes adapted to the LCHF diet. Third, endurance athletes exercising at >85%VO2max, whilst performing 6 × 800 m running intervals, measured the highest rates of fat oxidation yet reported in humans. Peak fat oxidation rates measured at 86.4 ± 6.2%VO2max were 1.58 ± 0.33 g/min with 30% of subjects achieving >1.85 g/min. These studies challenge the prevailing doctrine that carbohydrates are the predominant oxidized fuel during high-intensity exercise. We recently found that 30% of middle-aged competitive athletes presented with pre-diabetic glycemic values while on an HCLF diet, which was reversed on LCHF. We speculate that these rapid changes between diet, insulin, glucose homeostasis, and fat oxidation might be linked by diet-induced changes in mitochondrial function and insulin action. Together, we demonstrate evidence that challenges the current crossover concept and demonstrate evidence that a LCHF diet may also reverse features of pre-diabetes and future metabolic disease risk, demonstrating the impact of dietary choice has extended beyond physical performance even in athletic populations.

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).

A nutritional supplement based on a synbiotic combination of Bacillus subtilis DSM 32315 and L-alanyl-L-glutamine improves glucose metabolism in healthy prediabetic subjects - A real-life post-marketing study

Introduction

Impaired glucose homeostasis is a significant risk factor for cardiometabolic diseases, whereas the efficacy of available standard therapies is limited, mainly because of poor adherence. This post-marketing study assessed the glucose-lowering potential of a synbiotic-based formulation.

Methods

One hundred ninety-two participants were enrolled in a digital nutrition program with continuous glucose monitoring (CGM) and received a study product comprising Bacillus subtilis DSM 32315 and L-alanyl-L-glutamine. Participants underwent a first sensor phase without supplementation, followed by a 14-day supplementation phase without sensor, and completed by a second sensor phase while continuing supplementation. Fasting glucose levels were determined before and after supplementation by CGM. In addition, the postprandial glycemic response to an oral glucose challenge, body weight, HbA1c concentrations, and BMI was analyzed. Subgroup analyses of subjects with elevated glucose and HbA1c levels vs. normoglycemic subjects were performed.

Results

Supplementation with the study product resulted in significant improvements in glucose parameters (delta values: fasting glucose -2,13% ± 8.86; iAUC0-120 -4.91% ± 78.87; HbA1c: -1.20% ± 4.72) accompanied by a significant weight reduction (-1.07 kg ± 2.30) in the study population. Subgroup analyses revealed that the improvements were mainly attributed to a prediabetic subgroup with elevated fasting glucose and HbA1c values before supplementation (delta values: fasting glucose -6.10% 4± 7.89; iAUC0-120 -6.28% ± 115.85; HbA1c -3.31% ± 4.36; weight: -1.47 kg ± 2.82).

Conclusion

This study indicates that the synbiotic composition is an effective and convenient approach to counteract hyperglycemia. Further placebo-controlled studies are warranted to test its efficacy in the treatment of cardiometabolic diseases.