Effects of low-carbohydrate diets versus low-fat diets on metabolic risk factors in overweight and obese adults: A meta-analysis of randomized controlled trials

Hypocaloric low-carbohydrate versus low-fat diets on flow-mediated dilation, blood pressure, cardiovascular biomarkers, and body composition in individuals with overweight or obesity: a systematic review and meta-analysis of randomized clinical trials

Obesity can impair cardiometabolism, but low-carbohydrate diets (LCDs) may be beneficial for mitigating risk. We aimed to investigate the effects of LCDs versus low-fat diets (LFDs), under hypocaloric conditions, on flow-mediated dilation (FMD) in individuals with overweight/obesity. Secondarily, we assessed other cardiovascular markers (systolic blood pressure, diastolic blood pressure, C-reactive protein [CRP], high-density lipoprotein [HDL], low-density lipoprotein [LDL], triglycerides [TG], total cholesterol [TC]), and anthropometric and body composition measurements. PubMed, Scopus, and Web of Science were searched through May 2023 for studies involving hypocaloric LCDs versus LFDs on FMD. Meta-analyses were conducted for LCDs vs. LFDs to calculate weighted mean differences (WMD), including 10 studies reporting FMD (n = 475). Overall, hypocaloric LCDs resulted in a non-significant decrease in FMD compared with hypocaloric LFDs [WMD = -1.04% (95% CI -2.28 to 0.20), p = 0.10], while very-low-carbohydrate diets (VLCDs) significantly reduced FMD when compared with LFDs [WMD = -2.12% (95% CI: -3.35 to -0.9) p = 0.001]. LCDs did not change anthropometric and body composition measurements, nor CRP, blood pressure, HDL, or TC when compared with LFDs. However, LCDs significantly decreased TG [WMD = -19.94 mg/dL (95% CI -31.83 to -8.06), p = 0.001] and increased LDL [WMD = 20.00 mg/dL (95% CI 14.09 to 25.90), p = 0.001] when compared with LFDs. In conclusion, LCDs did not exert superior effects on cardiovascular markers or body composition when compared with LFDs in individuals with overweight or obesity, but LCDs reduced TG and increased LDL levels more than LFDs. Yet, vascular function (FMD) was reduced primarily for VLCDs.

Myths and Facts Regarding Low-Carbohydrate Diets

As the prevalence of chronic diseases persists at epidemic proportions, health practitioners face ongoing challenges in providing effective lifestyle treatments for their patients. Even for those patients on GLP-1 agonists, nutrition counseling remains a crucial strategy for managing these conditions over the long term. This paper aims to address the concerns of patients and practitioners who are interested in a low-carbohydrate or ketogenic diet, but who have concerns about its efficacy, safety, and long-term viability. The authors of this paper are practitioners who have used this approach and researchers engaged in its study. The paper reflects our opinion and is not meant to review low-carbohydrate diets systematically. In addressing common concerns, we hope to show that this approach has been well researched and can no longer be seen as a "fad diet" with adverse health effects such as impaired renal function or increased risk of heart disease. We also address persistent questions about patient adherence, affordability, and environmental sustainability. This paper reflects our perspective as clinicians and researchers engaged in the study and application of low-carbohydrate dietary interventions. While the paper is not a systematic review, all factual claims are substantiated with citations from the peer-reviewed literature and the most rigorous and recent science. To our knowledge, this paper is the first to address potential misconceptions about low-carbohydrate and ketogenic diets comprehensively.

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.

Metabolomics: Unveiling biological matrices in precision nutrition and health

Precision nutrition, an expanding field at the intersection of nutrition science and personalized medicine, is rapidly evolving with metabolomics integration. Metabolomics, facilitated by advanced technologies like mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy, facilitates comprehensive profiling of metabolites across diverse biological samples. From the perspective of health care systems, precision nutrition gains relevance due to the substantial impact of prevalent non-communicable diseases (NCDs) on societal well-being, which is directly linked with dietary habits and eating behavior. Furthermore, biomarker products derived from metabolomics have been utilized in Europe, the USA, and Brazil to understand metabolic dysregulations and tailor diets accordingly. Despite its burgeoning status, metabolomics holds great potential in revolutionizing nutritional science, particularly with the integration of artificial intelligence and machine learning, offering novel insights into personalized dietary interventions and disease prediction. This narrative review emphasizes the transformative impact of metabolomics in precision and delineates avenues for future research and application, paving the way for a more tailored and practical approach to nutrition management.

Short-term high-fat and high-carb diet effects on glucose metabolism and hedonic regulation in young healthy men

Background

Daily dietary intake of macronutrients and energy is closely associated with long-term metabolic health outcomes, but whether 24-h nutritional intervention under isocaloric conditions leads to changes in metabolism remains unclear. Moreover, the short-term effect of diets with different macronutrient composition on hedonic appetite regulation is less clear.

Methods

This study examined the impact of an acute high-fat (F+) and high-carbohydrate (C+) diet on glucose metabolism and hedonic regulation of food intake in young healthy men under controlled conditions. Using a cross-over design, 19 male participants received a one-day isocaloric diet with different macronutrient composition (F+ = 11% carbohydrates, 74% fat; C+ = 79% carbohydrates, 6% fat) compared to a control diet (CON = 55% carbohydrates, 30% fat). Protein content was set at 15% of energy in all diets. The feeling of hunger, as well as "liking" and "wanting" for foods, was assessed through visual analog scales, and blood samples for glucose, insulin, and cortisol levels were assessed repeatedly during the experimental day. An intravenous glucose tolerance test was conducted the next morning.

Results

Postprandial glucose and insulin levels were lowest in F+ over the 24 h. Except for dinner, the CON diet showed the highest mean values in glucose. F+ diet improved insulin resistance, lowering Homeostatis Model Assessment Insulin Resistance (HOMA-IR) values. Changes in hedonic regulation of food intake were not observed during the intervention between the diets, except for higher feelings of satiety under the CON diet.

Conclusion

An acute, isocaloric, high-fat diet improved insulin resistance even in healthy individuals but did not affect hedonic food intake regulation. Macronutrient composition modulate glucose metabolism even under short-term (24-h) and isocaloric diets, which should be considered for personalized preventive dietary treatments.

Prevention Strategies in Obesity Management: A Systematic Review Comparing Canadian and American Guidelines for Adults

The fast-increasing obesity prevalence rates in children, youths, and adults in the last decade have made obesity prevention a global public health priority. The primary objective of this study is to evaluate the various obesity prevention strategies and guidelines implemented in the United States and Canada. Thus, for this study, a systematic review was performed on various online databases including PubMed, Scopus, Google Scholar, and MEDLINE. The decision to study the obesity prevention strategies in Canada and the United States is a result of the high prevalence rates of obesity in the two countries, alongside the numerous prevention interventions that have been executed to prevent obesity. Additionally, the systematic review used robust methodology that followed the Cochrane guidance and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Only studies published between 2014 and 2024, drawn from listed databases, were included in this systematic review. The quality of the included studies was evaluated using the appraisal tool for cross-sectional studies, with the studies being rated moderate to high quality. Therefore, a total of 15 studies met the inclusion criteria and were reviewed. The findings indicate that various obesity prevention interventions have been implemented across the United States and Canada, with diverse degrees of success in obesity prevention and management. Food labeling, regular exercises, portion size regulation, school-based intervention strategies, early childhood Intervention programs, and sugar-sweetened beverage taxation were found to be effective interventions for preventing obesity in children and adults. Based on the findings, there is a need to ensure full execution of the different interventions to ensure significant reduction in obesity prevalence, as well as prevention of obesity in different populations.

Low-Carbohydrate Diet is More Helpful for Weight Loss Than Low-Fat Diet in Adolescents with Overweight and Obesity: A Systematic Review and Meta-Analysis

Purpose

This manuscript performed a meta-analysis to compare the effects of a low-fat diet (LFD) and a low-carbohydrate diet (LCD) on body weight and lipid levels in adolescents with overweight and obesity.

Patients and Methods

PubMed and other databases were searched for the full-text literature comparing LFD and LCD up to November 2023 using a subject plus free word strategy, with search terms such as "low-fat diet", "low-carbohydrate diet", "obesity", "weight", "adolescents", "RCT", and so on. Two independent reviewers selected promising candidate trials, collected the data, and assessed the quality of the trials. RevMan 5.3 software was utilized to conduct a meta-analysis of the randomized controlled trials (RCTs) that were included.

Results

5 RCTs with 192 participants were included in this meta-analysis. Weight (mean difference -2.81; 95% CI -5.38 to -0.25), Body Mass Index (BMI) (-1.13; 95% CI -2.14 to -0.11) and Triglyceride (TG) (-0.36; 95% CI -0.46 to -0.27) of the LCD were significantly lower than that of the LFD. At the same time, the high-density lipoprotein cholesterol (HDL) levels of the LCD were significantly higher than those of the LFD (0.08; 95% CI 0.04 to 0.12) (P < 0.05). However, there was no significant difference in the Homeostasis Model Assessment of Insulin Resistance (HOMA-IR), percent body fat, total cholesterol (TC), and low-density lipoprotein cholesterol (LDL) between the two groups (P>0.05).

Conclusion

According to this study, LCD is more helpful in improving weight loss, HDL and TG. Thus, LCD may serve as an effective intervention for weight management in adolescents with overweight and obesity, although further research is needed to determine its long-term effects.

The effect of a nurse-led low carbohydrate regimen on anthropometric and laboratory parameters of patients with metabolic syndrome: a quasi-experimental study

Introduction

Metabolic syndrome is a global health concern. It is a condition that includes a cluster of various risk factors for type 2 diabetes and cardiovascular disease. This quasi-experimental study investigates the effect of a nurse-led low-carbohydrate regimen on anthropometric and laboratory parameters in metabolic syndrome patients.

Methods

The study used a quasi-experimental design conducted at the University of Mosul; 128 participants meeting the metabolic syndrome criteria were recruited and divided into the intervention and control groups. The intervention group received personalized counseling and support in implementing a low-carb regime, while the control group received standard advice. The study participants were assessed by anthropometry, and laboratory parameters were evaluated pre- and post-intervention. Statistical data analysis was conducted using IBM-SPSS 27, including chi-square, Fisher's exact test, t-tests, and the Mcnemar test, which were performed to compare the changes within and between groups.

Results

The mean age of the participants in the intervention and control groups was 50.72 ± 6.43 years and 49.14 ± 6.89 years, respectively. Compared to the control group, the intervention group experienced a significant positive reduction in anthropometric measures and laboratory parameters, including weight, body mass index (BMI), waist circumference, lipid profiles, and HbA1c.

Conclusion

A tangible effect of nurse-led interventions based on low-carbohydrate regimens in managing metabolic syndrome was empirically authenticated. Positive changes were observed in the intervention group regarding anthropometric measures and laboratory parameters. However, future research may require a larger sample size and a longer follow-up to confirm these effects and evaluate long-term metabolic impacts.

The molecular mechanism of obesity: The science behind natural exercise yoga and healthy diets in the treatment of obesity

The review centers on the scientific evidence underlying obesity, providing a detailed examination of the role of perilipin in this condition. It explores potential causes of obesity and delves into therapeutic approaches involving exercise, yoga, and herbal treatments. The paper discusses natural sources that can contribute to combating obesity and underscores the importance of exercise in a scientific context for overcoming obesity. Additionally, it includes information on herbal ingredients that aid in reducing obesity. The review also examines the impact of exercise type and intensity at various time intervals on muscle development. It elucidates triglyceride hydrolysis through different enzymes and the deposition of fatty acids in adipose tissue. The mechanisms by which alpha/beta hydrolase domain-containing protein 5 (ABHD5) and hormone-sensitive lipase (HSL) target and activate their functions are detailed. The inflammatory response in obesity is explored, encompassing inflammatory markers, lipid storage diseases, and their classification with molecular mechanisms. Furthermore, the hormonal regulation of lipolysis is elaborated upon in the review.

A genomics perspective of personalized prevention and management of obesity

This review discusses the landscape of personalized prevention and management of obesity from a nutrigenetics perspective. Focusing on macronutrient tailoring, we discuss the impact of genetic variation on responses to carbohydrate, lipid, protein, and fiber consumption. Our bioinformatic analysis of genomic variants guiding macronutrient intake revealed enrichment of pathways associated with circadian rhythm, melatonin metabolism, cholesterol and lipoprotein remodeling and PPAR signaling as potential targets of macronutrients for the management of obesity in relevant genetic backgrounds. Notably, our data-based in silico predictions suggest the potential of repurposing the SYK inhibitor fostamatinib for obesity treatment in relevant genetic profiles. In addition to dietary considerations, we address genetic variations guiding lifestyle changes in weight management, including exercise and chrononutrition. Finally, we emphasize the need for a refined understanding and expanded research into the complex genetic landscape underlying obesity and its management.

Association between longitudinal dietary patterns and changes in obesity: a population-based cohort study

Introduction

Research on the trajectory of dietary patterns and changes in obesity has been inconclusive.

Methods

This study described the dietary intake and adiposity trajectories of Chinese adults and assessed the association between dietary trajectories and changes in body mass index (BMI) and waist-to-hip ratio (WHR). We used data from 3, 643 adults who participated in the China Health and Nutrition Survey from 1997 to 2015. Detailed dietary data were collected by conducting three consecutive 24-h recalls. Multitrajectories of diet scores were identified by a group-based multitrajectory method. We described the change in BMI and WHR using group-based trajectory modeling. We assessed the associations between dietary trajectories and changes in people with obesity using a logistic regression model.

Results

Our study revealed four trajectories of low-carbohydrate (LCD) and low-fat diet (LFD) scores. Three adiposity trajectories were identified according to the baseline level and developmental trend of BMI and WHR. Compared with the reference group, which was characterized by sustained healthy dietary habits with healthy diet scores at baseline and sustained maintenance of healthy diet scores, the other three diet trajectories had a higher risk of falling into the adverse adiposity trajectory.

Discussion

Maintaining a healthy LCD and LFD can markedly decrease the risk of adiposity.

Non-Classical Aspects of Obesity Pathogenesis and Their Relative Clinical Importance for Obesity Treatment

Obesity is a chronic disease and a major public health problem due to its association with non-communicable diseases and all-cause mortality. An increased energy intake and decreased physical activity have been long recognized as the classical parameters that contribute to the development of obesity. However, several other, non-classical factors have also been associated with obesity through various complex mechanisms. Some of them are diet related, such as diet quality, dietary habits and speed of eating. Other factors are non-dietary, such as endocrine-disrupting chemicals, sleep quality and quantity, psychotropic medications and light at night. The scope of the present narrative review is to address these non-classical factors that are implicated in the pathogenesis of obesity, to clarify their potential role in the management of obesity and, where possible, to provide some practical clinical recommendations.

Dietary patterns and cardiometabolic health: Clinical evidence and mechanism

For centuries, the search for nutritional interventions to underpin cardiovascular treatment and prevention guidelines has contributed to the rapid development of the field of dietary patterns and cardiometabolic disease (CMD). Numerous studies have demonstrated that healthy dietary patterns with emphasis on food-based recommendations are the gold standard for extending lifespan and reducing the risks of CMD and mortality. Healthy dietary patterns include various permutations of energy restriction, macronutrients, and food intake patterns such as calorie restriction, intermittent fasting, Mediterranean diet, plant-based diets, etc. Early implementation of healthy dietary patterns in patients with CMD is encouraged, but an understanding of the mechanisms by which these patterns trigger cardiometabolic benefits remains incomplete. Hence, this review examined several dietary patterns that may improve cardiometabolic health, including restrictive dietary patterns, regional dietary patterns, and diets based on controlled macronutrients and food groups, summarizing cutting-edge evidence and potential mechanisms for CMD prevention and treatment. Particularly, considering individual differences in responses to dietary composition and nutritional changes in organ tissue diversity, we highlighted the critical role of individual gut microbiota in the crosstalk between diet and CMD and recommend a more precise and dynamic nutritional strategy for CMD by developing dietary patterns based on individual gut microbiota profiles.