Beneficial Effects of the Ketogenic Diet in Metabolic Syndrome: A Systematic Review

Ketogenic Diet Intervention for Obesity Weight-Loss- A Narrative Review, Challenges, and Open Questions

PURPOSE OF REVIEW

The ketogenic diet (KD) has gained clinical attention for its potential benefits in weight loss and metabolic syndrome. By mimicking fasting through carbohydrate (CHO) restriction, KD shifts energy utilization to ketone bodies (KB) instead of glucose. Despite promising results, the effects on different weight loss indicators remain controversial, with challenges in monitoring adherence standards, optimal macronutrient composition, potential risks, and long-term sustainability. This article aims to review the different weight-loss outcomes of KD interventions for obesity, monitored by KB (adherence indication).

RECENT FINDINGS

Current literature on KD interventions for obesity weight loss monitored by KB show reduction in different outcomes, including body weight, body mass index, waist circumference, visceral adipose tissue, fat mass, and body fat percentage. Minor decreases in lean body mass and skeletal muscle mass were noted without resistance training. Variability existed in adherence (KB markers), CHO intake (7-27% of daily energy), diet duration (28 days to 12 months), and follow-up frequency (weekly to biannual). KD, particularly accompanied by exercise, positively influenced appetite regulation. KD interventions improves weight-related outcomes in participants with obesity but presents challenges in lean body mass reduction without resistance training and adherence variability. Standardizing methodologies, refining interventions and suitability to sub-populations, setting KB markers, and defining clinical relevance are essential for optimizing KD effectiveness.

Effects of ketogenic and low-carbohydrate diets on the body composition of adults with overweight or obesity: A systematic review and meta-analysis of randomised controlled trials

BACKGROUND AND AIMS

More than one-third of individuals are overweight and obese in the world. Their risks of chronic health conditions are increased, which places additional burden on their family, caregivers, and healthcare system. Dietary modification is widely used for overweight and obese individuals. We investigated the effects of ketogenic diet (KD) and low-carbohydrate diet (LCD) in improving body weight (BW), body mass index (BMI), fat mass (FM), and body fat percentage (BFP) in overweight or obese individuals.

METHODS

A three-step approach was adopted for searching relevant randomised controlled trials (RCTs) across five electronic databases. Two reviewers conducted the screening, review, and quality appraisal independently. A random-effects model was used because of variations in intervention and participant characteristics. Sensitivity and subgroup analyses were conducted to assess heterogeneity and variations in the results, respectively.

RESULTS

Thirty-three RCTs involving 2821 individuals were included. Overall meta-analysis results indicated that KD/LCD significantly reduced BW, BMI, and BFP, but not FM, in individuals with a carbohydrate intake of ≤100 g/d. Subgroup analyses revealed significant improvements in BW, BMI, and FM in individuals on KD/LCD for ≥1 month and in all parameters for those with a carbohydrate intake of ≤50 g/d. High statistical heterogeneity was noted because of variations in interventions and participant characteristics.

CONCLUSION

Adults with overweight or obesity should consume KD/LCD for ≥1 month and limit carbohydrate intake to ≤50 g/d. Further multicentre or multicountry RCTs are needed to improve the generalisability of our findings. We recommend integrating text messaging and evidence-based information to support interventions and ensuring stringent medical supervision throughout the intervention.

PROSPERO REGISTRATION NUMBER

CRD42022353074.

Effects of the Ketogenic Diet on Microbiota Composition and Short-Chain Fatty Acids in Women with Overweight/Obesity

Background/Objectives: The ketogenic diet (KD) is a dietary model that can impact metabolic health and microbiota and has been widely discussed in recent years. This study aimed to evaluate the effects of a 6-week KD on biochemical parameters, gut microbiota, and fecal short-chain fatty acids (SCFAs) in women with overweight/obesity. Methods: Overall, 15 women aged 26-46 years were included in this study. Blood samples, fecal samples, and anthropometric measurements were evaluated at the beginning and end of this study. Results: After KD, the mean body mass index decreased from 29.81 ± 4.74 to 27.12 ± 4.23 kg/m2, and all decreases in anthropometric measurements were significant (p < 0.05). Fasting glucose, insulin, homeostasis model assessment of insulin resistance, hemoglobin A1C, urea, and creatinine levels decreased, whereas uric acid levels increased (p < 0.05). Furthermore, increased serum zonulin levels were noted (p = 0.001), whereas fecal butyrate, propionate, acetate, and total SCFA levels decreased (p < 0.05). When the changes in microbiota composition were examined, a decrease in beta diversity (p = 0.001) was observed. After the intervention, a statistically significant increase was noted in the Firmicutes/Bacteroidetes ratio (p = 0.001). Although Oscilibacter, Blautia, and Akkermensia relative abundances increased, Prevotella relative abundance and Bifidobacter abundance, which were the dominant genera before the KD, decreased. Moreover, the abundance of some pathogenic genera, including Escherichia, Klebsilella, and Listeria, increased. Conclusions: In healthy individuals, KD may cause significant changes in microbial composition, leading to dysbiosis and long-term adverse outcomes with changes in serum zonulin and fecal SCFA levels.

Beneficial Effects of the Ketogenic Diet on Nonalcoholic Fatty Liver Disease (NAFLD/MAFLD)

The prevalence of nonalcoholic fatty liver disease (NAFLD) is likely to be approaching 38% of the world's population. It is predicted to become worse and is the main cause of morbidity and mortality due to hepatic pathologies. It is particularly worrying that NAFLD is increasingly diagnosed in children and is closely related, among other conditions, to insulin resistance and metabolic syndrome. Against this background is the concern that the awareness of patients with NAFLD is low; in one study, almost 96% of adult patients with NAFLD in the USA were not aware of their disease. Thus, studies on the therapeutic tools used to treat NAFLD are extremely important. One promising treatment is a well-formulated ketogenic diet (KD). The aim of this paper is to present a review of the available publications and the current state of knowledge of the effect of the KD on NAFLD. This paper includes characteristics of the key factors (from the point of view of NAFLD regression), on which ketogenic diet exerts its effects, i.e., reduction in insulin resistance and body weight, elimination of fructose and monosaccharides, limitation of the total carbohydrate intake, anti-inflammatory ketosis state, or modulation of gut microbiome and metabolome. In the context of the evidence for the effectiveness of the KD in the regression of NAFLD, this paper also suggests the important role of taking responsibility for one's own health through increasing self-monitoring and self-education.

Feasibility and acceptability of an online multicomponent very low-carbohydrate intervention in young adult women with obesity: a pilot study

BACKGROUND

Approximately one-third of US young adults (18-25 years) have obesity, and there are calls to help young adults lose weight to prevent weight-related chronic conditions. This pilot trial tested the feasibility and acceptability of a very low-carbohydrate (VLC) eating pattern, with supportive positive affect and mindful eating skills, for weight management among young females with obesity.

METHODS

In a single-arm trial, women (N = 17), aged 19-23, with obesity participated in a 4-month diet and lifestyle intervention. Participants were taught how to follow a VLC eating pattern with the help of a coach and 16 weekly web-based sessions. We assessed feasibility and acceptability through session participation, outcome collection, intervention satisfaction, and adverse events.

RESULTS

Seventeen participants enrolled and 14 (82%) reported body weight at 4 months. Fifteen participants (94% of those beginning the intervention) viewed at least one session, and 8/15 (53%) of these participants were active in the intervention, viewing at least half of the sessions. Among the nine participants who provided 4-month self-report information, intervention satisfaction was high (mean 5.89/7, 95% CI 4.59 to 7.19). Among participants with a 4-month body weight, 7/14 (50%) lost ≥ 5% of their body weight, and of those who were also active in the intervention, 6/7 (86%) lost ≥ 5% of their body weight. There were no serious adverse events.

CONCLUSIONS

The results of this pilot study suggest that a VLC eating pattern may be a feasible and acceptable approach for weight loss in some young women with obesity.

TRIAL REGISTRATION

This trial was registered with ClinicalTrials.gov on August 18, 2021. The trial number is NCT05010083.

Ketogenic Diet Plus Resistance Training Applied to Physio-Pathological Conditions: A Brief Review

The ketogenic diet (KD) is a nutritional strategy characterized by a reduced intake of carbohydrates (between 30 and 45 g per day or ≈5% of one’s total calories from this macronutrient). The regimen induces physiological ketosis in which serum levels of ketone bodies increase from 0.5 to 3.0 mM, becoming an essential contributor to energy production. The popularity of using the KD to lose weight and its application in specific physio-pathological conditions, such as epilepsy, lipedema, and polycystic ovary syndrome, which is maintained over extended periods, gave us the impulse to write this brief review. In these types of physio-pathological conditions, subjects can achieve favorable training outcomes even if adhering to a KD. Therefore, performing resistance training under the KD to enhance muscle status and quality of life could be possible. It is important to note that, while some statements here suggest potential future directions, they are hypotheses that require experimental validation, even if they are supported by the independent benefits reported from the KD and resistance training and represent a promising area for future research.

Hypercaloric low-carbohydrate high-fat diet protects against the development of nonalcoholic fatty liver disease in obese mice in contrast to isocaloric Western diet

Objective

Obesity and metabolic complications, such as type 2 diabetes and nonalcoholic fatty liver disease (NAFLD), are one of the greatest public health challenges of the 21st century. The major role of high sugar and carbohydrate consumption rather than caloric intake in obesity and NAFLD pathophysiology remains a subject of debate. A low-carbohydrate but high-fat diet (LCHFD) has shown promising results in obesity management, but its effects in preventing NAFLD need to be detailed. This study aims to compare the effects of a LCHFD with a high-fat high-sugar obesogenic Western diet (WD) on the progression of obesity, type 2 diabetes, and nonalcoholic fatty liver disease.

Methods

Male C57BL/6J mice were initially fed a WD for 10 weeks. Subsequently, they were either switched to a LCHFD or maintained on the WD for an additional 6 weeks. Hepatic effects of the diet were explored by histological staining and RT-qPCR.

Results

After the initial 10 weeks WD feeding, LCHF diet demonstrated effectiveness in halting weight gain, maintaining a normal glucose tolerance and insulin levels, in comparison to the WD-fed mice, which developed obesity, glucose intolerance, increased insulin levels and induced NAFLD. In the liver, LCHFD mitigated the accumulation of hepatic triglycerides and the increase in Fasn relative gene expression compared to the WD mice. Beneficial effects of the LCHFD occurred despite a similar calorie intake compared to the WD mice.

Conclusion

Our results emphasize the negative impact of a high sugar/carbohydrate and lipid association for obesity progression and NAFLD development. LCHFD has shown beneficial effects for NAFLD management, notably improving weight management, and maintaining a normal glucose tolerance and liver health.

Efficacy of convenience meal-type foods designed for diabetes in the management of metabolic syndrome based on a 3-week trial

OBJECTIVES

This study aimed to assess the effect of meal-type food for diabetes on improving metabolic syndrome risk factors in adults.

METHODS

The participants were adult men and women aged 40-55 y with 1 or more risk factors for metabolic syndrome. They were provided with a diabetic diet (a meal-type food) and general diet in the form of home meal replacement for 3 wk. The current research used a crossover design. All participants had iso-caloric meal replacement per day, and there was a 2-wk washout period between each diet. The nutritional standards of a diabetic diet were based on the guidelines of the Ministry of Food and Drug Safety, which are: <50% carbohydrates, <10% sugars, <7% saturated fat, and >10 g dietary fiber. The average caloric content was 489.1 ± 45.0 kcal. The composition of the general diet was similar to that of the diabetic diet; however, there were differences in sugar content. In total, 15 participants were included in the research, and there was no significant difference between the 2 groups in terms of nutrient intake during the intervention period.

RESULTS

Body weight (P = 0.001), body mass index (P = 0.004), waist circumference (P = 0.030), triacylglycerol (P = 0.002), total cholesterol (P = 0.001), and low-density lipoprotein cholesterol (P = 0.008) levels were significantly lower in the diabetic diet intervention period than before and after 3 wk of the intervention. In addition, reduction in body weight (P = 0.001), body mass index (P = 0.006), waist circumference (P = 0.032), and triacylglycerol (P = 0.036) and total cholesterol (P = 0.007) levels in the diabetic diet intervention period significantly differed compared with those in the general diet intervention period.

CONCLUSIONS

Replacing 1 meal per day with meal-type food for diabetes improved body composition and blood lipid levels in adults with metabolic syndrome risk factors.

A Potential Role for the Ketogenic Diet in Alzheimer's Disease Treatment: Exploring Pre-Clinical and Clinical Evidence

Given the remarkable progress in global health and overall quality of life, the significant rise in life expectancy has become intertwined with the surging occurrence of neurodegenerative disorders (NDs). This emerging trend is poised to pose a substantial challenge to the fields of medicine and public health in the years ahead. In this context, Alzheimer's disease (AD) is regarded as an ND that causes recent memory loss, motor impairment and cognitive deficits. AD is the most common cause of dementia in the elderly and its development is linked to multifactorial interactions between the environment, genetics, aging and lifestyle. The pathological hallmarks in AD are the accumulation of β-amyloid peptide (Aβ), the hyperphosphorylation of tau protein, neurotoxic events and impaired glucose metabolism. Due to pharmacological limitations and in view of the prevailing glycemic hypometabolism, the ketogenic diet (KD) emerges as a promising non-pharmacological possibility for managing AD, an approach that has already demonstrated efficacy in addressing other disorders, notably epilepsy. The KD consists of a food regimen in which carbohydrate intake is discouraged at the expense of increased lipid consumption, inducing metabolic ketosis whereby the main source of energy becomes ketone bodies instead of glucose. Thus, under these dietary conditions, neuronal death via lack of energy would be decreased, inasmuch as the metabolism of lipids is not impaired in AD. In this way, the clinical picture of patients with AD would potentially improve via the slowing down of symptoms and delaying of the progression of the disease. Hence, this review aims to explore the rationale behind utilizing the KD in AD treatment while emphasizing the metabolic interplay between the KD and the improvement of AD indicators, drawing insights from both preclinical and clinical investigations. Via a comprehensive examination of the studies detailed in this review, it is evident that the KD emerges as a promising alternative for managing AD. Moreover, its efficacy is notably enhanced when dietary composition is modified, thereby opening up innovative avenues for decreasing the progression of AD.

[Beneficial effects of ketogenic diet for Alzheimer's disease management]

Alzheimer's disease (AD) is a neurodegenerative disease that affects almost 1 million people in France and 55 million in the world. This pathology is a global health preoccupation because of the lack of efficient curative treatment and the increase of its prevalence. During the last decade, the comprehension of pathophysiological mechanisms involved in AD have been improved. Amyloid plaques and neurofibrillary tangles accumulation are characteristic of Alzheimer's brain patients, accompanied by increased brain inflammation and oxidative stress, impaired cerebral metabolism of glucose and mitochondrial function. Treatment of AD includes different approaches, as pharmacology, psychology support, physiotherapy, and speech therapy. However, these interventions do not have a curative effect, but only compensatory on the disease. Ketogenic diet (KD), a low-carbohydrates and high-fat diet, associated with a medium-chain triglycerides intake (MCTs) might induce benefices for Alzheimer disease patients. Carbohydrate restriction and MCTs promotes the production of ketone bodies from fatty acid degradation. These metabolites replacing glucose, serve the brain as energetic substrates, and induce neuroprotective effects. Such a nutritional support might slow down the disease progression and improve cognitive abilities of patients. This review aims to examine the neuroprotective mechanisms of KD in AD progression and describes the advantages and limitations of KD as a therapeutic strategy.

Acute Insulin Secretory Effects of a Classic Ketogenic Meal in Healthy Subjects: A Randomized Cross-Over Study

The classic ketogenic diet (KD) is a high-fat, low-carbohydrate diet that mimics a starvation state with sufficient caloric intake to sustain growth and development. KD is an established treatment for several diseases, and it is currently evaluated in the management of insulin-resistant states, although insulin secretion after a classic ketogenic meal has never been investigated. We measured the insulin secretion to a ketogenic meal in 12 healthy subjects (50% females, age range 19-31 years, BMI range 19.7-24.7 kg/m²) after cross-over administrations of a Mediterranean meal and a ketogenic meal both satisfying ~40% of an individual's total energy requirement, in random order and separated by a 7-day washout period. Venous blood was sampled at baseline and at 10, 20, 30, 45, 60, 90, 120, and 180 min to measure glucose, insulin, and C-peptide concentrations. Insulin secretion was calculated from C-peptide deconvolution and normalized to the estimated body surface area. Glucose, insulin concentrations, and insulin secretory rate were markedly reduced after the ketogenic meal with respect to the Mediterranean meal: glucose AUC in the first OGTT hour -643 mg × dL^-1 × min^-1, 95% CI -1134, -152, p = 0.015; total insulin concentration -44,943 pmol/L, 95% CI -59,181, -3706, p < 0.001; peak rate of insulin secretion -535 pmol × min^-1 × m^-2, 95% CI -763, -308, p < 0.001. We have shown that a ketogenic meal is disposed of with only a minimal insulin secretory response compared to a Mediterranean meal. This finding may be of interest to patients with insulin resistance and or insulin secretory defects.

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

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

Octanoic Acid-Enrichment Diet Improves Endurance Capacity and Reprograms Mitochondrial Biogenesis in Skeletal Muscle of Mice

Background: Medium Chain Fatty Acids (MCFAs) are a dietary supplement that exhibit interesting properties, due to their smaller molecular size. The acute consumption of MCFAs is expected to enhance exercise performance. However, the short-term effects of MCFAs on endurance performance remains poorly understood. The aim of our study is to evaluate the octanoic acid (C8)-rich diet effect on endurance capacity, and to explore their molecular and cellular effects. Methods: C57BL/6J mice were fed with a chow diet (Control group) or an octanoic acid-rich diet (C8 diet) for 6 weeks. Spontaneous activity, submaximal and maximal exercise tests were carried out to characterize the exercise capacities of the mice. Beta-oxidation and mitochondrial biogenesis pathways were explored in skeletal muscle by RT-qPCR, Western Blot (Quadriceps) and histochemical staining (Gastrocnemius). Results: Mice fed with a C8-rich diet presented a higher spontaneous activity (p < 0.05) and endurance capacities (p < 0.05) than the control, but no effect on maximal effort was observed. They also presented changes in the skeletal muscle metabolic phenotype, with a higher number of the oxidative fibers, rich in mitochondria. At the molecular level, the C8-diet induced an AMPK activation (p < 0.05), associated with a significant increase in PGC1a and CS gene expression and protein levels. Conclusion: Our study provided evidence that C8-enrichment as a food supplementation improves endurance capacities and activates mitochondrial biogenesis pathways leading to higher skeletal muscle oxidative capacities.