A 4-Week Preoperative Ketogenic Micronutrient-Enriched Diet Is Effective in Reducing Body Weight, Left Hepatic Lobe Volume, and Micronutrient Deficiencies in Patients Undergoing Bariatric Surgery: a Prospective Pilot Study

Effectiveness and Safety of Preoperative Nutritional Interventions on Surgical Outcomes in Patients Undergoing Metabolic and Bariatric Surgery: A Systematic Review and Meta-Analysis

Background: Preoperative nutritional interventions, including low-calorie diets (LCDs) and very low-calorie diets (VLCDs), are commonly implemented in metabolic and bariatric surgery. This systematic review and meta-analysis aimed to evaluate the efficacy and safety of preoperative dietary interventions in patients undergoing bariatric surgery, with primary outcomes including perioperative complications, operative time, and length of hospital stay. Methods: A systematic review and meta-analysis were conducted, including studies that compared LCD and VLCD with regular diets in adults undergoing bariatric surgery. The primary outcomes assessed were perioperative complications, operative time, and length of hospital stay. Random- and fixed effects models were used for quantitative synthesis. Risk of bias was evaluated using the Cochrane Risk of Bias tool and ROBINS-I, while the certainty of evidence was assessed using the GRADE approach. Results: Eight trials comprising 1197 patients were included in the meta-analysis. VLCDs were associated with a significant reduction in perioperative complications (OR 0.59; 95% CI: 0.37-0.94; p = 0.03), whereas LCDs showed no significant effect on complications (OR 1.64; 95% CI: 0.71-3.78; p = 0.25). No significant reduction in operative time was observed (MD -2.64 min; 95% CI: -6.01 to 0.73; p = 0.12). Hospital stay was slightly reduced (MD -0.17 days; p = 0.0001), though the clinical significance remains uncertain. The certainty of evidence was low, primarily due to the risk of bias and small sample sizes. Conclusions: VLCDs may lower the risk of perioperative complications, while LCDs do not appear to provide this benefit. However, the evidence is limited by methodological heterogeneity and low certainty. Further high-quality studies are needed to establish optimal preoperative nutritional protocols.

Preoperative weight loss by noninvasive approach in patients with obesity scheduled for bariatric and metabolic surgery: an update narrative review of indications and results available until 2024

Metabolic and bariatric surgery (MBS) is the most effective treatment for severe obesity and its metabolic complications. Currently, most MBSs are performed laparoscopically. However, high weight associated with an enlarged liver (especially the left lobe liver section, LLLS) may complicate the technical aspects of this surgery. Therefore, before MBS, moderate preoperative weight loss (PreopWL), and reduction in LLLS are desirable. Moreover, studies are inconclusive regarding which is the best approach to apply. This narrative review aimed to describe the current scientific evidence on the effect of a noninvasive approach, such as dietary or pharmacotherapy or space-occupying devices on PreopWL, peri-operative complications, hospital length of stay, and post-operative complications in patients with obesity scheduled for MBS. We conducted a literature search and screening for relevant publications from January 2010 to June 2024. We found that PreopWL before MBS is helpful for both patients and surgeons, as it leads to various benefits, such as a decrease in body weight and LLLS size, a lower risk of intra- and post-operative complications, shorter surgery times, and reduced hospital stays. In this context, concerning dietary approaches, several dietary protocols have been introduced over time, among which very low-calorie diets and very low energy ketogenic therapy are widely prescribed; however, larger randomized-controlled trials (RCTs) with well-defined dietary protocols are necessary to make definitive conclusions. Obesity management medications, such as the lipase inhibitor orlistat, phentermine/topiramate, naltrexone/bupropion, the glucagon-like peptide-1 receptor agonists (GLP-1RAs) liraglutide and semaglutide, and the novel dual glucose dependent insulinotropic peptide (GIP)/GLP-1 receptor agonist tirzepatide, has shown to be effective in promoting PreopWL before MBS; however, larger, well-designed RCTs are needed to establish optimal treatment protocols and assess their true benefits in patients scheduled for MBS. Space-occupying devices such as the swallowable intragastric balloon and hydrogel capsules, represent a promising tools but further research is essential to confirm their role.

Ketogenic Diet in Steatotic Liver Disease: A Metabolic Approach to Hepatic Health

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a major cause of chronic liver dysfunction worldwide, characterized by hepatic steatosis that may progress to nonalcoholic steatohepatitis and cirrhosis. Owing to its strong association with metabolic disorders, current management focuses on weight reduction via lifestyle modifications. Recently, the very-low-calorie ketogenic diet (VLCKD) has emerged as a promising intervention due to its potential for rapid weight loss and reduction in liver fat. This review aims to evaluate the clinical evidence regarding the impact of ketogenic diets on hepatic steatosis. We conducted an extensive MEDLINE literature search in databases including PubMed, Scopus, and Web of Science up to December 2024. Studies assessing the effects of ketogenic or low-carbohydrate high-fat diets on liver fat, evaluated by imaging, histology, or biochemical markers, were included. The analysis indicates that ketogenic diets significantly reduce hepatic fat content and improve metabolic parameters, including insulin sensitivity and liver enzyme levels. Evidence further suggests that substituting saturated fats with unsaturated fats or replacing carbohydrates with proteins may enhance these benefits. However, considerable variability exists among studies and long-term data remain limited. Although short-term outcomes are encouraging, potential adverse effects such as dyslipidaemia, gastrointestinal disturbances, and transient 'keto flu' symptoms require careful clinical monitoring. Future research should focus on elucidating underlying mechanisms, optimizing dietary composition, and assessing long-term safety to establish ketogenic diets as a robust strategy for managing MASLD.

Neurobiological and Microbiota Alterations After Bariatric Surgery: Implications for Hunger, Appetite, Taste, and Long-Term Metabolic Health

Bariatric surgery (BS) is an effective intervention for obesity, inducing significant neurobiological and gut microbiota changes that influence hunger, appetite, taste perception, and long-term metabolic health. This narrative review examines these alterations by analyzing recent findings from clinical and preclinical studies, including neuroimaging, microbiome sequencing, and hormonal assessments. BS modulates appetite-regulating hormones, reducing ghrelin while increasing glucagon-like peptide-1 (GLP-1) and peptide tyrosine-tyrosine (PYY), leading to enhanced satiety and decreased caloric intake. Neuroimaging studies reveal structural and functional changes in brain regions involved in reward processing and cognitive control, contributing to reduced cravings and altered food choices. Additionally, BS reshapes the gut microbiota, increasing beneficial species such as Akkermansia muciniphila, which influence metabolic pathways through short-chain fatty acid production and bile acid metabolism. These findings highlight the complex interplay between the gut and the brain in post-surgical metabolic regulation. Understanding these mechanisms is essential for optimizing post-operative care, including nutritional strategies and behavioral interventions. Future research should explore how these changes impact long-term outcomes, guiding the development of targeted therapies to enhance the recovery and quality of life for BS patients.

Preliminary Evidence Suggests That a 12-Week Treatment with Tirzepatide Plus Low-Energy Ketogenic Therapy Is More Effective than Its Combination with a Low-Calorie Diet in Preserving Fat-Free Mass, Muscle Strength, and Resting Metabolic Rate in Patients with Obesity

Background: Tirzepatide (TZP), a unimolecular dual agonist targeting glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 receptors, is a promising weight loss agent in obesity. The preservation of metabolically active fat-free mass (FFM), muscle strength (MS), and resting metabolic rate (RMR) is essential for optimizing fat mass (FM) reduction. Although TZP is typically combined with a low-calorie diet (LCD), its impact on FFM is uncertain, and studies on MS and RMR are lacking. Evidence suggests that Low-Energy Ketogenic Therapy (LEKT) may reduce FM while preserving FFM, MS, and RMR. Therefore, this study aimed to compare the effects of an LEKT and an LCD, both combined with TZP, on body weight (BW), FM, FFM, MS, and RMR in patients with obesity. Methods: We prospectively compared the effects of TZP combined with either an LCD or LEKT in 60 patients with obesity (n = 30 per group) over 12 weeks. BW, FM, FFM, MS, and RMR were measured at baseline and after 12 weeks. Clinical parameters, an assessment of dietary compliance, and side effects were also evaluated. Results: At 12-week follow-up, both groups showed a significant BW reduction from baseline (TZP+LEKT, p = 0.0289; TZP+LCD, p = 0.0278), with no significant intergroup difference (p = 0.665). Similarly, FM decreased significantly in both cohorts (TZP+LEKT, p < 0.001; TZP+LCD, p = 0.0185), with the TZP+LEKT group achieving a greater FM loss (p = 0.042). However, the TZP+LCD group exhibited significant declines from baseline in FFM (p = 0.0284), MS (p = 0.0341), and RMR (p < 0.001), whereas we did not observe any significant changes in FFM (p = 0.487), MS (p = 0.691), and RMR (p = 0.263) in the TZP+LEKT group. Intergroup direct comparisons confirmed that the TZP+LCD group experienced significantly greater reductions in FFM (p = 0.0388), MS (p = 0.046), and RMR (p = 0.019). Conclusions: Based on the findings of these preliminary data, we are able to support the hypothesis that TZP+LEKT seems to be superior to TZP+LCD in promoting FM reduction while preserving FFM, MS, and RMR in patients with obesity.

Preventing and Managing Pre- and Postoperative Micronutrient Deficiencies: A Vital Component of Long-Term Success in Bariatric Surgery

Bariatric surgery (BS) is an effective treatment for severe obesity and its related comorbidities, such as type 2 diabetes and hypertension. However, the anatomical and physiological changes associated with these procedures significantly increase the risk of preoperative and postoperative micronutrient deficiencies, which can lead to severe complications such as anemia, osteoporosis, and neurological disorders. This narrative review examines the prevalence and clinical implications of micronutrient deficiencies in BS patients, as well as evidence-based strategies for their prevention and management. The most common deficiencies include iron, vitamin B12, folate, calcium, vitamin D, and fat-soluble vitamins (A, E, and K). Procedures with a hypoabsorptive component, such as Roux-en-Y gastric bypass (RYGB) and biliopancreatic diversion with duodenal switch (BPD/DS), pose higher risks of deficiencies compared to restrictive procedures like sleeve gastrectomy (SG). Effective strategies involve the preoperative correction of deficiencies, continuous monitoring, and tailored supplementation. However, long-term adherence to supplementation tends to decrease over time, influenced by behavioral and socioeconomic factors. Hence, preventing and managing micronutrient deficiencies are crucial for the long-term success of BS. While current guidelines provide valuable recommendations, many are based on low-certainty evidence, underscoring the need for more robust studies. A multidisciplinary approach, combined with innovative strategies, such as telemedicine, can enhance adherence and achieve sustainable clinical outcomes.

Optimizing Nutritional Management Before and After Bariatric Surgery: A Comprehensive Guide for Sustained Weight Loss and Metabolic Health

Obesity is associated with multiple comorbidities that contribute to increased mortality among affected individuals. There are multiple treatments for this condition, including nutritional interventions, pharmacological therapies, and surgical procedures. Within these, bariatric surgery is an effective treatment option that requires a multidisciplinary approach, both before and after surgery. Nutritional management prior to surgery aims to achieve metabolic control and reduce comorbidities associated with the procedure. Postoperative nutritional management focuses on preventing complications, ensuring adequate nourishment, and providing necessary supplementation for optimal recovery and long-term success. This narrative review examines all these critical aspects of nutritional management in bariatric surgery, including preoperative nutrition, postoperative nutrition and physical activity recommendation, different nutritional aspects according to the type of bariatric surgery, and future directions for investigation.

Preoperative Nutrition in Bariatric Surgery: A Narrative Review on Enhancing Surgical Success and Patient Outcomes

Bariatric surgery has become the preferred treatment for individuals with morbid obesity. Nutrition is key in optimizing surgical outcomes by reducing risks and enhancing recovery. Preoperative strategies, such as reducing body fat, decreasing liver size, and improving metabolic profiles, have been shown to facilitate safer surgical procedures with fewer complications. This narrative review aims to provide an analysis of the fundamental role of preoperative nutritional management in improving bariatric surgery outcomes, emphasizing the importance of addressing specific nutritional challenges to enhance surgical safety, recovery, and overall health. Preoperative nutritional interventions focus on correcting comorbidities and nutritional deficiencies, particularly hypovitaminosis and micronutrient imbalances, through a multidisciplinary approach involving nutritionists and other healthcare professionals. These interventions not only prepare patients for the physiological demands of surgery but also initiate a period of adaptation to new dietary habits, aiming to improve long-term compliance and mitigate risks such as postoperative weight regain and dumping syndrome. Adopting dietary changes, such as very low-calorie or ketogenic diets 6-12 weeks before surgery, enhances adherence to postoperative restrictions and overall surgical success. Future research should focus on developing comprehensive guidelines for preoperative nutritional care to improve patient outcomes globally.

A Very Low-Carbohydrate Program in Adults With Metabolic Dysfunction-Associated Steatotic Liver Disease and Phospholipase Domain-Containing Protein 3 Risk Genotype: Pre-Post Intervention Study

Background

Insulin resistance and the G allele of rs738409 interact to create a greater risk of metabolic dysfunction-associated steatotic liver disease.

Objective

This study aims to confirm that one promising way to reduce insulin resistance is by following a very low-carbohydrate (VLC) dietary pattern.

Methods

Adults with rs738409-GG or -CG with liver steatosis and elevated liver function tests, were taught an ad libitum VLC diet, positive affect and mindful eating skills, goal setting, and self-monitoring and given feedback and coaching for 4 months. We measured liver steatosis, anthropometric, serum metabolic diet adherence, and quality of life measures.

Results

In this small pilot trial, of the 11 participants enrolled, 9 (82%) participants completed outcomes. All 11 participants viewed at least 1 session of the intervention, and 8 (73%) participants viewed at least half of the sessions. Among the 9 participants who provided 4-month self-report information, intervention satisfaction was high (mean 6.22, 95% CI 5.58-6.85), with 5 (56%) participants rating the intervention the top score, and 4 (44%) participants reporting they did not plan to stop following the VLC diet. Across participants with a 4-month hepatic liver fat percent measurement, the percent change in liver fat was -33.17% (95% CI -86.48 to 20.14), and in only the participants who were adherent to the eating pattern, the percent change in liver fat was -53.12% (95% CI -71.25 to -34.99). Amongst participants with a 4-month hepatic liver fat percent measurement, 6 out of 8 (75%) participants were considered responders, with a relative decline in liver fat ≥30%, and of the 9 participants with a 4-month body weight, 9 (100%) participants lost ≥5% of their body weight. There were no serious adverse events.

Conclusions

Results suggest the feasibility, acceptability, and preliminary efficacy of the VLC intervention in adults with higher genetic risk for metabolic dysfunction-associated steatotic liver disease, although there is a need for further studies given the small sample size and the high risk of substantial biases in this small pilot study.

Safety and Effectiveness of a 4-Week Diet on Low-Carb Ready-to-Eat Ketogenic Products as Preoperative Care Treatment in Patients Scheduled for Metabolic and Bariatric Surgery

Before metabolic and bariatric surgery (MBS), moderate weight loss and liver left lateral section (LLLS) volume reduction are desirable. Low-carb ketogenic diet-induced weight loss before MBS has been shown to have beneficial effects on the reduction in body weight (BW) and LLLS. However, the nutritional protocol of low-carb ketogenic diet may be hard to keep for prolonged periods due to the lack of sweet taste. Furthermore, transitioning to a low-carb ketogenic diet can cause people to crave foods that are restricted in the ketogenic diet, such as cookies, bread, pasta, and bagels. Therefore, many ready-to-eat low-carb ketogenic products (RLCKP) that mimic carbohydrate-rich foods despite a low-carb composition have been provided to make it easier for the patients to adopt a low-carb lifestyle. To date, there are no studies describing the dietary protocol for efficient and safe use of pre-operative RLCKP in terms of weight and LLLS volume reduction in patients with obesity scheduled for MBS. Therefore, the aim of this study was to assess the safety and effectiveness of a 4-week diet using RLCKP in reducing BW and LLLS volume in patients with obesity scheduled for MBS. Patients with obesity (n = 42) with a mean body mass index (BMI) of 42.4 ± 9.2 kg/m2 scheduled for MBS underwent a 4-week preoperative RLCKP diet intervention. Their weight, LLLS volume, and biochemical and metabolic parameters were measured before and after the diet. Patient compliance was assessed by the presence of ketonuria and weight loss. Qualitative methods (5-point Likert questionnaire) were used to measure diet acceptability and side effects. All patients completed the study. We observed highly significant decreases in BW (-6.5%, p < 0.001), and LLLS volume (-22.3%, p < 0.001) and an amelioration of patient clinical status. All patients showed a high frequency of acceptability and compliance in following the diet. No adverse side effects were reported. Based on our findings, we were able to support the hypothesis that a 4-week preoperative RLCKP diet is safe and effective in reducing BW, and LLLS volume in patients with obesity scheduled for MBS.

Protocol for a feasibility multi-centre randomised controlled trial of a pre-operative two-week very low-calorie diet to reduce steatosis prior to liver resection (RESOLVE)

BACKGROUND

Hepatic steatosis (HS) increases morbidity and mortality associated with liver surgery (LS). Furthermore, patients with HS are more likely to require a blood transfusion, which is associated with worse short and long-term outcomes. Patients with HS requiring LS receive no specific dietary treatment or advice. A very low-calorie diet (VLCD) is commonly used before gallbladder and bariatric surgery to reduce liver volumes and associated intraoperative morbidity. These diets typically provide 800-1200 kcal/day over a 2-4-week period. Limited evidence suggests that a VLCD in patients with LS may result in better outcomes.

METHODS

This study aims to test the feasibility of delivering a multi-centre randomised clinical trial to compare a dietary intervention (VLCD plus motivational instructions) versus treatment as usual (TAU) in people with HS having LS. This study will provide high-quality data to estimate screening rates, recruitment, randomisation, retention, and intervention adherence. The study will also determine the definitive trial's most clinically relevant primary outcome. The study will also estimate resource use and costs associated with the delivery of the intervention. Seventy-two adults ≥ 18 who are scheduled to undergo elective LS and have a magnetic resonance imaging (MRI) identified HS will be recruited. Acceptability to the dietary intervention will be evaluated with food diaries and focus groups. Clinical and patient-reported outcomes will be collected at baseline, pre- and post-surgery, day of discharge, plus 30- and 90-day follow-up.

DISCUSSION

This feasibility study will provide data on the acceptability and feasibility of a dietary intervention for patients with HS having LS. The intervention has been developed based on scientific evidence from other clinical areas and patient experience; therefore, it is safe for this patient group. Patients with experience of LS and VLCDs have advised throughout the development of the study protocol. The findings will inform the design of a future definitive study.

TRIAL REGISTRATION

ISRCTN Number 19701345. Date registered: 20/03/2023. URL: https://www.isrctn.com/ISRCTN19701345 .

Nutritional Considerations During Major Weight Loss Therapy: Focus on Optimal Protein and a Low-Carbohydrate Dietary Pattern

PURPOSE OF REVIEW

Considering the high prevalence of obesity and related metabolic impairments in the population, the unique role nutrition has in weight loss, reversing metabolic disorders, and maintaining health cannot be overstated. Normal weight and well-being are compatible with varying dietary patterns, but for the last half century there has been a strong emphasis on low-fat, low-saturated fat, high-carbohydrate based approaches. Whereas low-fat dietary patterns can be effective for a subset of individuals, we now have a population where the vast majority of adults have excess adiposity and some degree of metabolic impairment. We are also entering a new era with greater access to bariatric surgery and approval of anti-obesity medications (glucagon-like peptide-1 analogues) that produce substantial weight loss for many people, but there are concerns about disproportionate loss of lean mass and nutritional deficiencies.

RECENT FINDINGS

No matter the approach used to achieve major weight loss, careful attention to nutritional considerations is necessary. Here, we examine the recent findings regarding the importance of adequate protein to maintain lean mass, the rationale and evidence supporting low-carbohydrate and ketogenic dietary patterns, and the potential benefits of including exercise training in the context of major weight loss. While losing and sustaining weight loss has proven challenging, we are optimistic that application of emerging nutrition science, particularly personalized well-formulated low-carbohydrate dietary patterns that contain adequate protein (1.2 to 2.0 g per kilogram reference weight) and achieve the beneficial metabolic state of euketonemia (circulating ketones 0.5 to 5 mM), is a promising path for many individuals with excess adiposity.

Low-calorie diets are effective for weight loss in patients undergoing benign upper gastrointestinal surgery: a systematic review and meta-analysis

BACKGROUND

Obesity may increase surgical complexity in patients undergoing abdominal surgery by limiting visualization and increasing the risk of peri-operative complications. A preoperative reduction in weight and liver volume may improve surgical outcomes. The aim of our study was to evaluate the efficacy of a low-calorie diet (LCD) versus a very low-calorie diet (VLCD) in reducing weight and liver volume prior to laparoscopic surgery.

METHODS

A systematic search was conducted using the following inclusion criteria: obese patients undergoing preoperative weight loss using a VLCD or LCD, evaluation of liver volume reduction, and the use of an imaging modality before and after the diet.

RESULTS

A total of 814 patients from 21 different studies were included in this systematic review and meta-analysis, with 544 female patients (66.8%) and a mean age range between 24 and 54 years old. There was a total mean weight loss of 6.42% and mean liver volume reduction of 16.7%. Meta-analysis demonstrated that a preoperative diet (LCD or VLCD) significantly reduced weight [SMD = - 0.68; 95% CI (- 0.93, - 0.42), I2 = 82%, p ≤ 0.01] and liver volume [SMD = - 2.03; 95% CI (- 4.00, - 0.06), I2 = 94%, p ≤ 0.01]. When assessed individually, a VLCD led to significant weight reduction [SMD = - 0.79; CI (- 1.24; - 0.34), p ≤ 0.01, I2 = 90%], as did an LCD [SMD = - 0.60; CI (- 0.90; - 0.29), p ≤ 0.01, I2 = 68%). Similarly, there was a significant reduction in liver volume following a VLCD [SMD = - 1.40; CI (- 2.77, - 0.03), p ≤ 0.01, I2 = 96%], and an LCD [SMD = - 2.66; CI (- 6.13, 0.81), p ≤ 0.01, I2 = 93%]. However, there was no significant difference between the two regimens.

CONCLUSIONS

Preoperative restrictive calorie diets are effective in reducing weight and liver volume prior to laparoscopic surgery. Whilst a VLCD was better than an LCD at reducing both weight and liver volume, the difference was not significant.

Beyond Obesity and Overweight: the Clinical Assessment and Treatment of Excess Body Fat In Children : Part 2 - the Prescription of Low-Carbohydrate Eating as the First Approach

PURPOSE OF REVIEW

Pediatric obesity and comorbidities related to insulin resistance continue to be a growing public health crisis. If lifestyle measures are unsuccessful, pharmacological and surgical interventions are offered. In this paper, we describe the driving force of the obesity crisis: hyperinsulinemia and the development of insulin resistance. We give historical background of key policy issues which have contributed to this pandemic as well as the physiologic mechanisms of insulin resistance. The prevalence of obesity will continue to rise unless the root cause of hyperinsulinemia is addressed.

RECENT FINDINGS

Current research on insulin resistance demonstrates that a decreased consumption of carbohydrates is an effective first-line dietary intervention for the treatment of obesity and related metabolic diseases. Evidence shows it is safe and beneficial. A low-carbohydrate eating pattern can be helpful to address pediatric obesity. However, there must be policy guardrails in place to ensure that this is a sustainable and viable option for children and their families. There must be a change in the nutritional environment to help individuals battle the chronic disease of obesity.

Very low-carbohydrate diet with higher protein ratio improves lipid metabolism and inflammation in rats with diet-induced nonalcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is commonly associated with obesity, and it is mainly treated through lifestyle modifications. The very low-carbohydrate diet (VLCD) can help lose weight rapidly but the possible effects of extreme dietary patterns on lipid metabolism and inflammatory responses in individuals with NAFLD remain debatable. Moreover, VLCD protein content may affect its effectiveness in weight loss, steatosis, and inflammatory responses. Therefore, we investigated the effects of VLCDs with different protein contents in NAFLD rats and the mechanisms underlying these effects. After a 16-week inducing period, the rats received an isocaloric normal diet (NC group) or a VLCD with high or low protein content (NVLH vs. NVLL group, energy ratio:protein/carbohydrate/lipid=20/1/79 vs. 6/1/93) for the next 8 weeks experimental period. We noted that the body weight decreased in both the NVLH and NVLL groups; nevertheless, the NVLH group demonstrated improvements in ketosis. The NVLL group led to hepatic lipid accumulation, possibly by increasing very-low-density lipoprotein receptor (VLDLR) expression and elevating liver oxidative stress, subsequently activating the expression of Nrf2, and inflammation through the TLR4/TRIF/NLRP3 and TLR4/MyD88/NF-κB pathway. The NVLH was noted to prevent the changes in VLDLR and the TLR4-inflammasome pathway partially. The VLCD also reduced the diversity of gut microbiota and changed their composition. In conclusion, although low-protein VLCD consumption reduces BW, it may also lead to metabolic disorders and changes in microbiota composition; nevertheless, a VLCD with high protein content may partially alleviate these limitations.

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.

Ketogenic diet alleviates β-cell dedifferentiation but aggravates hepatic lipid accumulation in db/db mice

OBJECTIVE

The aim of this study was to explore the effect of the ketogenic diet (KD) on β-cell dedifferentiation and hepatic lipid accumulation in db/db mice.

METHODS

After a 3-wk habituation, male db/db mice ages 8 wk were assigned into one of three groups: normal diet (ND), KD, and 75% calorie restriction (CR) group. Free access to a standard diet, a KD, and 75% of a standard diet, respectively, were given to each group. Additionally, sex-matched 8-wk-old C57BL/6 mice were used to construct a control (C) group. After a 4-wk dietary intervention, mouse body weight, fasting blood glucose (FBG), blood lipids, fasting insulin (FINS), glucose tolerance, and β-hydroxybutyric acid level were measured. The morphologies of the islet and liver were observed by hematoxylin and eosin staining. Positive expressions of β-cell-specific transcription factors in mouse islets were determined by double immunofluorescence staining. The size and number of lipid droplets in mouse liver were examined by Oil Red O staining. Real-time quantitative reverse transcription polymerase chain reaction detected relative levels of adipogenesis-associated and lipolysis-associated genes in mouse liver. Additionally, expressions of CD36 protein in the mouse liver were determined by immunohistochemical staining and Western blot.

RESULTS

After a 4-wk dietary intervention, FBG, FINS, and glucose area under the curve in the KD group became significantly lower than in the ND group (all P < 0.05). Regular morphology of mouse islets was observed in the KD group, with an increased number of islet cells. The KD significantly reversed the decrease in β-cell number, disarrangement of β-cells, decline of β/α-cell ratio, and downregulation of β-cell-specific transcription factors in db/db mice. Serum levels of triacylglycerol, total cholesterol, and low-density lipoprotein cholesterol were comparable between the ND and KD groups. In contrast, serum triacylglycerol levels were significantly lower in the CR group than in the ND group (P < 0.05). Vacuolar degeneration and lipid accumulation in the liver were more prominent in the KD group than in the ND and CR groups. The mRNA levels of Pparα and Acox1 in the KD group were lower than those in the ND group, although no significant differences were detected. Relative levels of Cd36 and inflammatory genes in the mouse liver were significantly higher in the KD group than in the ND group (all P < 0.05).

CONCLUSION

The KD significantly reduced FBG and FINS and improved glucose tolerance in db/db mice by upregulating β-cell-specific transcription factors and reversing β-cell dedifferentiation. However, the KD also induced hepatic lipid accumulation and aggravated inflammatory response in the liver of db/db mice.

Requirements for essential micronutrients during caloric restriction and fasting

Caloric restriction (CR) or energy restriction, when carefully designed, monitored, and implemented in self-motivated and compliant individuals, proves to be a viable non-pharmacologic strategy for human weight control and obesity management. Beyond its role in weight management, CR has the potential to impede responses involved not only in the pathogenesis of various diseases but also in the aging process in adults, thereby being proposed to promote a healthier and longer life. The core objective of implementing caloric restriction is to establish a balance between energy intake and expenditure, typically involving a reduction in intake and an increase in expenditure-a negative balance at least initially. It may transition toward and maintain a more desired equilibrium over time. However, it is essential to note that CR may lead to a proportional reduction in micronutrient intake unless corresponding supplementation is provided. Historical human case reports on CR have consistently maintained adequate intakes (AI) or recommended dietary allowances (RDA) for essential micronutrients, including vitamins and minerals. Similarly, longevity studies involving non-human primates have upheld micronutrient consumption levels comparable to control groups or baseline measures. Recent randomized controlled trials (RCTs) have also endorsed daily supplementation of multivitamins and minerals to meet micronutrient needs. However, aside from these human case reports, limited human trials, and primate experiments, there remains a notable gap in human research specifically addressing precise micronutrient requirements during CR. While adhering to AI or RDA for minerals and vitamins appears sensible in the current practice, it's important to recognize that these guidelines are formulated for generally healthy populations under standard circumstances. The adequacy of these guidelines in the setting of prolonged and profound negative energy balance remains unclear. From perspectives of evidence-based medicine and precision nutrition, this field necessitates comprehensive exploration to uncover the intricacies of absorption, utilization, and metabolism and the requirement of each hydrophilic and lipophilic vitamin and mineral during these special periods. Such investigations are crucial to determine whether existing daily dietary recommendations for micronutrients are quantitatively inadequate, excessive, or appropriate when energy balance remains negative over extended durations.

Changes in Macronutrients during Dieting Lead to Weight Cycling and Metabolic Complications in Mouse Model

Weight cycling is a major challenge in obesity management. Caloric restriction is known to promote this phenomenon, but the impact of macronutrient changes during dieting remains unclear. This study aimed to determine the role of macronutrient changes in weight maintenance without caloric restriction by alternating between two hypercaloric diets: a high-carbohydrate, high-fat Western diet (WD) and a low-carbohydrate, high-fat diet (LCHDF). Obesity was induced in 8-week-old C57BL/6 male mice by 10 weeks of WD feeding. Then, the mice were subjected to 12 weeks of LCHFD interspersed with WD (I-WD), 3 periods of 2-week LCHFD followed by 2 periods of 3-week WD, or 12 weeks of continuous WD (C-WD). C-WD and I-WD mice were compared to standard diet (SD) mice. In the I-WD group, each LCHFD period decreased weight gain, but mice regained weight after WD resumption. I-WD mice exhibited obesity, dyslipidemia, and glucose intolerance, similarly to the C-WD mice. I-WD mice also developed nonalcoholic steatohepatitis, associated with an increase in type-III collagen gene expression and a decrease in FGF21 protein levels, in comparison with SD. I-WD mice developed weight cycling despite maintaining a high caloric consumption, suggesting that changes in macronutrients during dieting are also a trigger of weight regain.

Keto Menu-Effect of Ketogenic Menu and Intermittent Fasting on the Biochemical Markers and Body Composition in a Physically Active Man-A Controlled Case Study

The combination of ketogenic diet (KD) with intermittent fasting (IF) has, for years, aroused a great interest in the scientific world and among healthy lifestyle enthusiasts. Its importance is even greater when the study subjects are physically active individuals. The aim of the study was a determination of the effect of strict calculated ketogenic menu combined with IF and with caloric deficit on the selected biochemical markers and body composition in a 23-year-old man performing strength training. At the same time, we decided to conduct the first so-deeply investigated and controlled case study in this respect. The study protocol included a 13-week-long ketogenic diet with intermittent fasting (of delayed time-restricted eating 16:8 type) and caloric deficit. A detailed menu was designed and was used by the man throughout the whole study duration. A number of blood tests were performed before and after the implemented dietary intervention. Additionally, body composition was determined weekly and the concentrations of glucose and ketone bodies, as well as pulse rate and arterial pressure, were measured daily. The most important changes noted included a significant increase in testosterone and vitamin D concentrations and significant reduction in the HOMA-IR index and concentrations of hepatic enzymes, insulin, glucose, iron, urea, and free triiodothyronine (FT3). Moreover, a significant improvement of body composition occurred (the ratio of total body mass to the adipose and muscular tissue and water mass improved). Favourable changes were also noted in heart rate and arterial pressure values. In view of that, the KD with IF and caloric deficit exerted favourable effects on most biochemical parameters and on body composition and caused an almost twofold increase in serum testosterone concentration.

Very Low-Calorie Ketogenic Diet (VLCKD) as Pre-Operative First-Line Dietary Therapy in Patients with Obesity Who Are Candidates for Bariatric Surgery

Bariatric surgery is currently the most effective method for achieving long-term weight loss and reducing the risk of comorbidities and mortality in individuals with severe obesity. The pre-operative diet is an important factor in determining patients' suitability for surgery, as well as their post-operative outcomes and success in achieving weight loss. Therefore, the nutritional management of bariatric patients requires specialized expertise. Very low-calorie diets and intragastric balloon placement have already been studied and shown to be effective in promoting pre-operative weight loss. In addition, the very low-calorie ketogenic diet has a well-established role in the treatment of obesity and type 2 diabetes mellitus, but its potential role as a pre-operative dietary treatment prior to bariatric surgery has received less attention. Thus, this article will provide a brief overview of the current evidence on the very low-calorie ketogenic diet as a pre-operative dietary treatment in patients with obesity who are candidates for bariatric surgery.

Clinical Impact of Enteral Protein Nutritional Therapy on Patients with Obesity Scheduled for Bariatric Surgery: A Focus on Safety, Efficacy, and Pathophysiological Changes

BACKGROUND

Ketogenic diet-induced weight loss before bariatric surgery (BS) has beneficial effects on the reduction in the liver volume, metabolic profile, and intra- and post-operative complications. However, these beneficial effects can be limited by poor dietary adherence. A potential solution in patients showing a poor adherence in following the prescribed diet could be represented by enteral nutrition strategies. To date, no studies describe the protocol to use for the efficacy and the safety of pre-operative enteral ketogenic nutrition-based dietary protocols in terms of weight reduction, metabolic efficacy, and safety in patients with obesity scheduled for BS.

AIMS AND SCOPE

To assess the clinical impact, efficacy, and safety of ketogenic nutrition enteral protein (NEP) vs. nutritional enteral hypocaloric (NEI) protocols on patients with obesity candidate to BS.

PATIENTS AND METHODS

31 NEP were compared to 29 NEI patients through a 1:1 randomization. The body weight (BW), body mass index (BMI), waist circumference (WC), hip circumference (HC), and neck circumference (NC) were assessed at the baseline and at the 4-week follow-up. Furthermore, clinical parameters were assessed by blood tests, and patients were asked daily to report any side effects, using a self-administered questionnaire.

RESULTS

Compared to the baseline, the BW, BMI, WC, HC, and NC were significantly reduced in both groups studied (p < 0.001). However, we did not find any significative difference between the NEP and NEI groups in terms of weight loss (p = 0.559), BMI (p= 0.383), WC (p = 0.779), and HC (p = 0.559), while a statistically significant difference was found in terms of the NC (NEP, -7.1% vs. NEI, -4%, p = 0.011). Furthermore, we found a significant amelioration of the general clinical status in both groups. However, a statistically significant difference was found in terms of glycemia (NEP, -16% vs. NEI, -8.5%, p < 0.001), insulin (NEP, -49.6% vs. NEI, -17.8%, p < 0.0028), HOMA index (NEP, -57.7% vs. NEI, -24.9%, p < 0.001), total cholesterol (NEP, -24.3% vs. NEI, -2.8%, p < 0.001), low-density lipoprotein (NEP, -30.9% vs. NEI, 1.96%, p < 0.001), apolipoprotein A1 (NEP, -24.2% vs. NEI, -7%, p < 0.001), and apolipoprotein B (NEP, -23.1% vs. NEI, -2.3%, p < 0.001), whereas we did not find any significative difference between the NEP and NEI groups in terms of aortomesenteric fat thickness (p = 0.332), triglyceride levels (p = 0.534), degree of steatosis (p = 0.616), and left hepatic lobe volume (p = 0.264). Furthermore, the NEP and NEI treatments were well tolerated, and no major side effects were registered.

CONCLUSIONS

Enteral feeding is an effective and safe treatment before BS, with NEP leading to better clinical results than NEI on the glycemic and lipid profiles. Further and larger randomized clinical trials are needed to confirm these preliminary data.

SICOB-endorsed national Delphi consensus on obesity treatment optimization: focus on diagnosis, pre-operative management, and weight regain/insufficient weight loss approach

PURPOSE

Overweight and obesity affects 60% of adults causing more than 1.2 million deaths across world every year. Fight against involved different specialist figures and multiple are the approved weapons. Aim of the present survey endorsed by the Italian Society of Bariatric Surgery (SICOB) is to reach a national consensus on obesity treatment optimization through a Delphi process.

METHODS

Eleven key opinion leaders (KOLs) identified 22 statements with a major need of clarification and debate. The explored pathways were: (1) Management of patient candidate to bariatric/metabolic surgery (BMS); (2) Management of patient not eligible for BMS; (3) Management of patient with short-term (2 years) weight regain (WR) or insufficient weight loss (IWL); (4) Management of the patient with medium-term (5 years) WR; and (5) Association between drugs and BMS as WR prevention. The questionnaire was distributed to 65 national experts via an online platform with anonymized results.

RESULTS

54 out of 65 invited panelists (83%) respond. Positive consensus was reached for 18/22 statements (82%); while, negative consensus (s20.4; s21.5) and no consensus (s11.5, s17) were reached for 2 statements, respectively (9%).

CONCLUSION

The Delphi results underline the importance of first-line interdisciplinary management, with large pre-treatment examination, and establish a common opinion on how to properly manage post-operative IWL/WR.

LEVEL OF EVIDENCE V

Report of expert committees.

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.

The effect of isocaloric, energy-restrictive, KETOgenic diet on metabolism, inflammation, nutrition deficiencies and oxidative stress in women with overweight and obesity (KETO-MINOX): Study protocol

Obesity is considered one of the biggest health problems of the 21st century, becoming a worldwide epidemic, leading to the development of many diseases and increasing the risk of premature death. The first step in reducing body weight is a calorie-restricted diet. To date, there are many different diet types available, including the ketogenic diet (KD) which is recently gaining a lot of attention. However, all the physiological consequences of KD in the human body are not fully understood. Therefore, this study aims to evaluate the effectiveness of an eight-week, isocaloric, energy-restricted, KD as a weight management solution in women with overweight and obesity compared to a standard, balanced diet with the same calorie content. The primary outcome is to evaluate the effects of a KD on body weight and composition. The secondary outcomes are to evaluate the effect of KD-related weight loss on inflammation, oxidative stress, nutritional status, profiles of metabolites in breath, which informs about the metabolic changes in the body, obesity and diabetes-associated parameters, including a lipid profile, status of adipokines and hormones. Notably, in this trial, the long-term effects and efficiency of the KD will be studied. In summary, the proposed study will fill the gap in knowledge about the effects of KD on inflammation, obesity-associated parameters, nutritional deficiencies, oxidative stress and metabolism in a single study. ClinicalTrail.gov registration number: NCT05652972.

The Effect of the Restrictive Ketogenic Diet on the Body Composition, Haematological and Biochemical Parameters, Oxidative Stress and Advanced Glycation End-Products in Young Wistar Rats with Diet-Induced Obesity

Over the past few years, the interest in the application of the ketogenic diet (KD) for obesity management is growing. Although many studies have been performed on the effects of KD, the metabolic and physiological impact of KD is still not fully understood. Therefore, this study aimed to evaluate the effect of calorie-restricted KD on the body weight and composition, oxidative stress, and advanced glycation end products (AGEs) assessed in an animal model with young Wistar rats. KD was followed for 4 weeks in maturity after an obesity-inducing high-fat diet during adolescence, resulting in a slowing down of the weight gain but higher adiposity compared to a standard diet. Increased adiposity resulted in an deterioration of liver parameters, suggesting negative changes in this organ. No adverse effects of KD were determined in haematological parameters in young rats. KD did not affect AGEs; however, a decrease in oxidative stress was observed. Based on the presented results, it can be concluded that KD applied for weight loss in obesity induced in adolescence may reduce oxidative stress without compromising the haematological status; however, caution may be required to control adiposity, glucose level and liver health. Thus, KD therapy should be carefully controlled, especially in young subjects.

Differences in weight loss outcomes for males and females on a low-carbohydrate diet: A systematic review

It has been widely demonstrated that there are a broad range of individual responses to all weight management regimens, often masked by reports of the mean. Identifying features of responders and non-responders to weight loss regimens enables a more tailored approach to the provision of weight management advice. Low-carbohydrate diets are currently popular, and anecdote suggests that males are more successful at losing weight using this approach. This is feasible given the physiological and socio-psychological differences between the genders. We analysed the extent and variation in weight change for males and females separately through a systematic search for all low-carbohydrate diet trials published since 1985. Very few studies compared weight loss outcomes by gender and, of those that did, most lacked supporting data. The majority of studies reported no gender difference but when a gender difference was found, males were more frequently reported as losing more weight than females on a low-carbohydrate diet. The lack of gender stratification in weight loss trials is concerning, as there are a range of gender-based factors that affect weight loss outcomes. This study highlights the importance of examining weight change for males and females separately, since as failure to do so may mask any potential differences, which, if detected, could assist with better weight loss outcomes.

The Impact of Bariatric-Surgery-Induced Weight Loss on Patients Undergoing Liver Transplant: A Focus on Metabolism, Pathophysiological Changes, and Outcome in Obese Patients Suffering NAFLD-Related Cirrhosis

Because of their condition, patients with morbid obesity develop several histopathological changes in the liver, such as non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatohepatitis (NASH), cirrhosis, and end-stage liver disease (ESLD). Hence, a liver transplant (LT) becomes an opportune solution for them. Due to many challenges during the perioperative and postoperative periods, these patients are recommended to lose weight before the surgery. There are many proposals to achieve this goal, such as intragastric balloons and many different bariatric surgery (BS) procedures in combination with a preparation diet (very-low-calorie diet, ketogenic diet, etc.). All the interventions focus on losing weight and keeping the continuity and functionality of the digestive tract to avoid postoperative complications. Thus, this review analyzes recent publications regarding the metabolic and pathophysiological impacts of BS in LT patients suffering from NAFLD-related cirrhosis, the effect of weight loss on postoperative complications, and exposes the cost-effectiveness of performing BS before, after, and at liver transplantation. Finally, the authors recommend BS before the LT since there are many positive effects and better outcomes for patients who lose weight before the procedure. Nevertheless, further multicentric studies are needed to determine the generalizability of these recommendations due to their impact on public health.

Ketogenic Diet for Preoperative Weight Reduction in Bariatric Surgery: A Narrative Review

Bariatric surgery (BS) is the most effective treatment in reducing weight and the burden of comorbidities in patients with severe obesity. Despite the overall low mortality rate, intra- and post-operative complications remains quite common. Weight loss before BS reduces surgical risk, but studies are inconclusive regarding which is the best approach to apply. In this review, we summarize the current evidence on the effect of a ketogenic diet (KD) before BS. All studies agree that KD leads to considerable weight loss and important improvements in terms of surgical risk, but populations, interventions and outcomes are very heterogeneous. KD appears to be a safe and effective approach to induce weight loss before BS. However, randomized controlled trials with better-defined dietary protocols and homogeneous outcomes are necessary in order to draw firm conclusions.

Higher Preoperative Weight loss Is Associated with Greater Weight Loss up to 12 Months After Bariatric Surgery

BACKGROUND

Prior research suggested presurgical weight loss is associated with greater total weight loss, resulting in a more effective bariatric intervention. We aimed to assess whether preoperative weight loss is a predictor for total weight loss, and which patient factors are associated with successful weight loss.

METHODS

All patients (N = 773) that underwent primary bariatric surgery between June 2017 and August 2019 were included in this single-center retrospective study. Outcome measures were preoperative weight loss (%preopWL) and total weight loss (%TWL) up to 1 year postoperatively. Patients were divided into 4 groups based on quartiles of %preopWL.

RESULTS

Total weight loss after 1, 6, and 12 months for the upper quartile was 16.9%, 33.4%, and 37.8%, and for the lower quartile 11.8%, 28.9%, and 35.2%, respectively (p < 0.001). Seven hundred fourteen patients (92.4%) were available for the 1-year follow-up. Preoperative weight loss was not associated with the incidence of complications. Independent factors predicting increased %preopWL were mandated preoperative weight loss program (MWP) (p < 0.001), older age (p = 0.005), weight measurement in the week before surgery (p = 0.031), and non-diabetic status (p = 0.010). Predictors for superior %TWL were MWP (p = 0.014), younger age (p = 0.001), non-diabetic status (p = 0.005), female gender (p = 0.001), higher Body Mass Index (p = 0.006), and banded gastric bypass (p = 0.001).

CONCLUSION

Higher preoperative weight loss is associated with persisting greater weight loss up to at least 12 months post-surgery. In order to optimize preoperative weight loss, we recommend extra preoperative support to younger and diabetic patients. We advise nutritional counseling and additional weight measurement in the week before surgery.

Holistic Approach in the Management of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD), in a few decades, is expected to be the commonest cause of end-stage liver disease and liver cancer surpassing all other etiologies. Urbanization and modern lifestyle have led to global epidemic of NAFLD with alarming prevalence rates across the globe. Its multisystemic involvement manifests as metabolic syndrome, diabetes, cardiovascular disease, end-stage liver disease, and hepatic and extrahepatic malignancies. The absence of promising therapy for halting disease progression in NAFLD is a challenge that is not only limited to liver disease but also other organs involved. It is unrealistic to expect any significant impact of pharmacotherapies in overall survival of NAFLD patients, given that the morbidity and mortality in these patients are contributed by conditions other than that of liver. Liver-centric approach in managing NAFLD will be futile unless the problem is dealt in a holistic manner. Lifestyle modifications have been repeatedly appraised in prevention and treatment of various diseases linked to metabolic syndrome including NAFLD. Despite being inexpensive and highly efficacious in prevention and treatment of different manifestations of NAFLD, lifestyle intervention often fails to gather sufficient interest among patients and physicians alike. This review intends to highlight pleiotropic nature of this disease, limitations of currently available pharmacotherapies and evidence that emphasizing lifestyle intervention is the only way to holistically deal in patients with NAFLD.

HOW TO CITE THIS ARTICLE

Shrestha A, Pradhananga S. Holistic Approach in the Management of Nonalcoholic Fatty Liver Disease. Euroasian J Hepato-Gastroenterol 2022;12(Suppl 1):S51-S58.

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

Metabolic syndrome (MetS) is a major societal concern due to its increasing prevalence and its high risk of cardiovascular complications. The ketogenic diet (KD), a high fat, low carbohydrate, and non-caloric restrictive diet, is a new popular weight loss intervention but its beneficial effects are controversial. This study aims to gather all of the relevant studies using KD for metabolic disease treatment to determine its beneficial effects and evaluate its safety and efficacy for patients. Following the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses, we included 20 articles in the final review. Overall, most of the studies showed a significant effect of KD on weight loss (17/19 articles), BMI (7/7), glucose levels (9/13), insulin levels (7/9), HOMA-IR (4/5), HbA1c (7/7), total cholesterol (6/9), TG (13/15), AST (3/4), and ALT (3/5), and no major side effects. The results heterogeneity seems to be explained by a difference of diet composition and duration. In conclusion, KD is a safety diet which seems to be a promising approach for obesity and MetS treatment, even if the optimal carbohydrate proportion and diet duration must be explored to enhance the beneficial effects of KD.

Impact of SARS-CoV-2 Lockdown on the Preoperative Care Program of Patients Scheduled for Bariatric Surgery

Objectives: To evaluate the effect of the SARS-CoV-2 lockdown on dietary habits, body weight, left hepatic lobe volume, use of micronutrient supplements, micronutrient status, frequency of physical activity, and evolution of comorbidities in patients undergoing preoperative care for BS. Materials and Methods: We prospectively evaluated the dietary habits (including use of micronutrient supplements and frequency of physical activity) of 36 patients who were candidates for BS from March to May 2020; 7-day food dietary records, body weight, left hepatic lobe volume by ultrasound, micronutrient status, and evolution of comorbidities were assessed. Results: All patients completed the study. Of the participants, 44.4% (16/36), 47.2% (17/36), and 27.8% (10/36) followed the preoperative indications for vegetables, fruits, and legumes, respectively, whereas over 50% did not. Furthermore, 30.6% (11/36) and 55.6% (20/36) of participants followed the prescribed recommendations for carbohydrates/sweets products and alcohol, respectively. A total of 61.1% (22/36) of participants experienced new foods and new culinary preparations. In addition, at the time of the study, we found that only 11.1% (4/36) were engaged in prescribed physical activity and only 36.1% (13/36) were taking prescribed micronutrient supplements. Compared to the initial weight, we observed an increased body weight and body mass index (+4.9%, p = 0.115; +1.89%, p = 0.0692, respectively), and no improvement in left hepatic lobe volume, micronutrient status, or comorbidities was recorded for any patient in the anamnesis. Conclusions: Lockdown determined by the SARS-CoV-2 pandemic has negatively affected the preoperative program of BS candidates, resulting in a postponement to the resumption of bariatric surgical activity.

Low-Calorie Ketogenic Diet with Continuous Positive Airway Pressure to Alleviate Severe Obstructive Sleep Apnea Syndrome in Patients with Obesity Scheduled for Bariatric/Metabolic Surgery: a Pilot, Prospective, Randomized Multicenter Comparative Study

Obstructive sleep apnea syndrome (OSAS) and obesity are frequently associated with hypertension (HTN), dyslipidemia (DLP), and insulin resistance (IR). In patients with obesity and OSAS scheduled for bariatric surgery (BS), guidelines recommend at least 4 weeks of preoperative continuous positive airway pressure (CPAP). Low-calorie ketogenic diets (LCKDs) promote pre-BS weight loss (WL) and improve HTN, DLP, and IR. However, it is unclear whether pre-BS LCKD with CPAP improves OSAS more than CPAP alone. We assessed the clinical advantage of pre-BS CPAP and LCKD in patients with obesity and OSAS. Seventy patients with obesity and OSAS were randomly assigned to CPAP or CPAP+LCKD groups for 4 weeks. The effect of each intervention on the apnea–hypopnea index (AHI) was the primary endpoint. WL, C-reactive protein (CRP) levels, HTN, DLP, and IR were secondary endpoints. AHI scores improved significantly in both groups (CPAP, p=0.0231; CPAP+LCKD, p=0.0272). However, combining CPAP and LCKD registered no advantage on the AHI score (p=0.863). Furthermore, body weight, CRP levels, and systolic/diastolic blood pressure were significantly reduced in the CPAP+LCKD group after 4 weeks (p=0.0052, p=0.0161, p=0.0008, and p=0.0007 vs baseline, respectively), and CPAP+LCKD had a greater impact on CRP levels than CPAP alone (p=0.0329). The CPAP+LCKD group also registered a significant reduction in serum cholesterol, LDL, and triglyceride levels (p=0.0183, p=0.0198, and p<0.001, respectively). Combined with CPAP, LCKD-induced WL seems to not have a significant incremental effect on AHI, HTN, DLP, and IR but lower CRP levels demonstrated a positive impact on chronic inflammatory status.

A Randomized, Controlled Trial Comparing the Impact of a Low-Calorie Ketogenic vs a Standard Low-Calorie Diet on Fat-Free Mass in Patients Receiving an Elipse™ Intragastric Balloon Treatment

BACKGROUND

The Elipse™ intragastric balloon (EIGB) is a new swallowable balloon for weight loss (WL). Preserving metabolically active fat-free mass (FFM) and resting metabolic rate (RMR) during WL are crucial to maximize fat mass (FM) loss. After EIGB placement, a standard low-calorie diet (LCD) is generally prescribed. A low-calorie ketogenic diet (LCKD) has proven to be safe and effective in reducing FM while preserving FFM and RMR.

OBJECTIVE

To prospectively compare the effects on WL, FM, FFM, and RMR in two groups of patients who were randomized to two different diets: LCKD and a standard LCD after EIGB placement.

METHODS

WL, FM, FFM, and RMR were measured before EIGB and at 4 months in 48 patients who received either a LCKD (n = 24) or a standard LCD (n = 24). Compliance in following the prescribed diet was determined with food frequency questionnaires in all patients. The impact of LCKD and LCD on renal function was also evaluated.

RESULTS

The LCKD group showed a significantly lower decrease in FFM and RMR when compared with the LCD group (3.55 vs 14.3%, p < 0.001; 9.79 vs 11.4%, p < 0.001, respectively). FM decreased more significantly with LCKD compared to LCD (41.6 vs 33.1%, p = 0.0606). Compliance in following the prescribed diets, without negative impact on renal function, was found.

CONCLUSION

Based on our findings, despite the small sample size, we were able to support the hypothesis that LCKD is associated with an increased FM loss while reducing the FFM loss and the RMR, without interfering with renal function after EIGB.

Nerve injury and repair in a ketogenic milieu: A systematic review of traumatic injuries to the spinal cord and peripheral nervous tissue

Dietary interventions such as intermittent fasting and the ketogenic diet have demonstrated neuroprotective effects in various models of neurological insult. However, there has been a lack of evaluation of these interventions from a surgical perspective despite their potential to augment reparative processes that occur following nerve injury. Thus, we sought to analyze the effects of these dietary regimens on nerve regeneration and repair by critical appraisal of the literature. Following PRISMA guidelines, a systematic review was performed to identify studies published between 1950 and 2020 that examined the impact of either the ketogenic diet or intermittent fasting on traumatic injuries to the spinal cord or peripheral nerves. Study characteristics and outcomes were analyzed for each included article. A total of 1,890 articles were reviewed, of which 11 studies met inclusion criteria. Each of these articles was then assessed based on a variety of qualitative parameters, including type of injury, diet composition, timing, duration, and outcome. In total, seven articles examined the ketogenic diet, while four examined intermittent fasting. Only three studies examined peripheral nerves. Neuroprotective effects manifested as either improved histological or functional benefits in most of the included studies. Overall, we conclude that intermittent fasting and the ketogenic diet may promote neuroprotection and facilitate the regeneration and repair of nerve fibers following injury; however, lack of consistency between the studies in terms of animal models, diet compositions, and timing of dietary interventions preclude synthesis of their outcomes as a whole.

Ketogenic Diets and Cardio-Metabolic Diseases

While the prevalence of cardio-metabolic diseases (CMDs) has become a worldwide epidemic, much attention is paid to managing CMDs effectively. A ketogenic diet (KD) constitutes a high-fat and low-carbohydrate diet with appropriate protein content and calories. KD has drawn the interests of clinicians and scientists regarding its application in the management of metabolic diseases and related disorders; thus, the current review aimed to examine the evidences surrounding KD and the CMDs to draw the clinical implications. Overall, KD appears to play a significant role in the therapy of various CMDs, which is manifested by the effects of KDs on cardio-metabolic outcomes. KD therapy is generally promising in obesity, heart failure, and hypertension, though different voices still exist. In diabetes and dyslipidemia, the performance of KD remains controversial. As for cardiovascular complications of metabolic diseases, current evidence suggests that KD is generally protective to obese related cardiovascular disease (CVD), while remaining contradictory to diabetes and other metabolic disorder related CVDs. Various factors might account for the controversies, including genetic background, duration of therapy, food composition, quality, and sources of KDs. Therefore, it's crucial to perform more rigorous researches to focus on clinical safety and appropriate treatment duration and plan of KDs.

Beneficial effects of the ketogenic diet on nonalcoholic fatty liver disease: A comprehensive review of the literature

Nonalcoholic fatty liver disease (NAFLD) is a major cause of chronic liver disease, characterized by hepatic fat accumulation and possible development of inflammation, fibrosis, and cancer. The ketogenic diet (KD), with its drastic carbohydrate reduction, is a now popular weight loss intervention, despite safety concerns on a possible association with fatty liver. However, KDs were also reported to be beneficial on hepatic pathology, with ketone bodies recently proposed as effective modulators of inflammation and fibrosis. If the beneficial impact of weight loss on NAFLD is established, less is known on the effect of macronutrient distribution on such outcome. In a hypocaloric regimen, the latter seems not to be crucial, whereas at higher calorie intake, macronutrient ratio and, theoretically, ketosis, may become important. KDs could positively impact NAFLD for their very low carbohydrate content, and whether ketosis plays an additional role is unknown. Indeed, several mechanisms may directly link ketosis and NAFLD improvement, and elucidating these aspects would pave the way for new therapeutic strategies. We herein aimed at providing an accurate revision of current literature on KDs and NAFLD, focusing on clinical evidence, metabolic pathways involved, and strict categorization of dietary interventions.

Long-Term Results of the Mediterranean Diet After Sleeve Gastrectomy

BACKGROUND

To assess dietary habits in a cohort of patients at minimum follow-up of 4 years after sleeve gastrectomy (SG) by comparing their dietary records to the Italian Mediterranean diet (IMD) recommendations.

METHODS

We prospectively evaluated in 74 patients who had the SG in 2014 dietary habits by a 7-day food dietary records, weight and micronutrient status, evolution of comorbidities, use of micronutrient supplements, and frequency of physical activity.

RESULTS

The IMD recommendations in terms of daily/weekly portions of fruits, vegetables, and complex carbohydrates were followed by 40.5%, 35.1%, and 40.5% of the participants, respectively. Concerning milk/dairy, olive oil, poultry, fish/shellfish, eggs, legumes, processed/red meat, and cold cuts, 54.1%, 85.1%, 44.5%, 75.7%, 67.6%, 35.1%, 87.8%, and 55.4% of the participants, respectively, followed the IMD recommendations. Weight regain appeared in 37.8% of participants, while physical activity was reported by the 54.0% of them. Deficiencies of vitamin B12, vitamin D, folate, iron, and anemia were found present in 6.8%, 8.1%, 24.3%, 33.8%, and 59.5% of the participants, respectively, and 18.9% of them were found to take micronutrient supplements. Improvement/remission of type 2 diabetes, hypertension, or obstructive sleep apnea was 73.3%, 64.7%, and 100% respectively.

CONCLUSIONS

In this prospective cohort with a minimum follow-up of 4 years after SG, we found an inadequate intake of fruit, vegetables, poultry, and complex carbohydrates according to the IMD recommendations; the frequency of physical activity and the use of micronutrients supplements were also inadequate. This may contribute to weight regain and micronutrient deficiencies in the long term.

Clinical factors correlated with vitamin D deficiency in patients with obesity scheduled for bariatric surgery: A single center experience

We aim to assess the prevalence of vitamin D deficiency (VDD) in patients scheduled for bariatric surgery (BS), and to identify factors that might be associated with VDD. We conducted a cross-sectional observational study involving all consecutive patients scheduled for BS from 2017 to 2019. The exclusion criteria were missing data for vitamin D levels, intake of vitamin D supplements in the 3 months prior to serum vitamin D determination, and renal insufficiency. A total of 206 patients (mean age and body mass index [BMI] of 34.9 ± 10.7 years, and 44.3 ± 6.99 kg/m², respectively) met the inclusion criteria and were enrolled for data analysis. VDD (<19.9 ng/mL), severe VDD (<10 ng/mL), and vitamin D insufficiency (20-29.9 ng/mL) were present in 68.8 %, 12.5 %, and 31.2 % of patients, respectively. A significant inverse correlation was found between vitamin D levels and initial BMI, parathyroid hormone, and homeostatic model assessment of insulin resistance (r = -0.280, p < 0.05; r = -0.407, p = 0.038; r = -0.445, p = 0.005), respectively. VDD was significantly more prevalent in patients with higher BMI [-0.413 ± 0.12, CI95 % (-0.659; -0.167), p = 0.006], whereas no significant association between hypertension [-1.005 ± 1.65, CI95 % (-4.338; 2.326), p = 0.001], and diabetes type 2 (T2D) [-0.44 ± 2.20, CI95 % (-4.876; 3.986), p = 0.841] was found. We observed significant association between female sex and levels of vitamin D [6.69 ± 2.31, CI95 % (2.06; 11.33), p = 0.006]. The present study shows that in patients scheduled for BS, VDD deficiency is common and was associated with higher BMI, and female sex.

Confusion in the nomenclature of ketogenic diets blurs evidence

Ketogenic diets have been proposed as a non-pharmacological strategy for the management of several chronic conditions. Their efficacy and safety have been evaluated in the field of neurology, oncology and endocrinology for disorders including cancer, dementia, drug-resistant epilepsy, migraines, obesity, polycystic ovary syndrome and type 2 diabetes mellitus. The nutritional requirements of these subjects are expected to differ significantly. Indeed, although all ketogenic diets restrict carbohydrates, each intervention is characterized by a specific daily calorie intake, macronutrient composition and duration. However, the adopted nomenclature was often unclear to the general reader; also, the same abbreviations for different protocols were used. This possibly resulted in mistakes in the interpretation of the available evidence and limited the impact of studies on the topic in the clinical practice. Adopting a clear and consistent vocabulary is key in any context. Here, we present a practical and clinically-based proposal for the classification and abbreviation of ketogenic diets.

Very-low-calorie ketogenic diet (VLCKD) in the management of metabolic diseases: systematic review and consensus statement from the Italian Society of Endocrinology (SIE)

BACKGROUND

Weight loss is a milestone in the prevention of chronic diseases associated with high morbility and mortality in industrialized countries. Very-low calorie ketogenic diets (VLCKDs) are increasingly used in clinical practice for weight loss and management of obesity-related comorbidities. Despite evidence on the clinical benefits of VLCKDs is rapidly emerging, some concern still exists about their potential risks and their use in the long-term, due to paucity of clinical studies. Notably, there is an important lack of guidelines on this topic, and the use and implementation of VLCKDs occurs vastly in the absence of clear evidence-based indications.

PURPOSE

We describe here the biochemistry, benefits and risks of VLCKDs, and provide recommendations on the correct use of this therapeutic approach for weight loss and management of metabolic diseases at different stages of life.

A ketogenic diet for reducing obesity and maintaining capacity for physical activity: hype or hope?

PURPOSE OF REVIEW

This review will evaluate the recent scientific literature on the efficacy of the ketogenic diet for enhancing weight loss and maintaining capacity for physical activity.

RECENT FINDINGS

With the increasing obesity epidemic, the 21st century has witnessed the emergence of various diet programs aimed at promoting weight loss and enhancing physical performance. The ketogenic diet, a diet high in fat and low in carbohydrates, has been at the forefront. Recent literature has documented significant weight-loss following ketogenic diet interventions. This has been associated with a decrease in systemic inflammation, reduced insulin resistance, and improved lipid profile. Given the importance of physical activity to sustaining a healthy weight, the impact of a ketogenic diet on physical performance has been investigated. The majority of the current literature supports a positive influence of the ketogenic diet on physical activity owing to its ability to maintain performance of both endurance and resistance activities. We highlight the most important recent advances that have been made on the ketogenic diet in relation to obesity and capacity for physical activity.

SUMMARY

The ketogenic diet is a potentially promising diet for reducing obesity while maintaining capacity for physical activity. However, questions surrounding the sustainability of this diet for the long-term remain.

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.

Correcting micronutrient deficiencies before sleeve gastrectomy may be useful in preventing early postoperative micronutrient deficiencies

Micronutrient deficiencies (MD) shortly after sleeve gastrectomy (SG) are frequent and patients with obesity often show MD preoperatively. Our aim was to assess whether the correction of MD before SG could play a role in preventing early postoperative MD. Eighty patients (58 females, 22 males) who underwent SG were evaluated retrospectively. Patients were divided according to whether they had received preoperative MD correction (Group A, n = 42; 30 females, 12 males) or not (Group B, n = 38; 28 females, 10 males). Micronutrient status was assessed preoperatively, at 3 and 12-months after SG in both groups. After SG, Group A and Group B patients received the same multivitamin supplement and followed the same diet. Nutrient intake of all patients was evaluated by food frequency questionnaires. Before SG, patients of Group A had no MD, whereas patients of Group B were mostly deficient in vitamin B12 (10.5%, 3 women, 1 man), folate (15.8%, 5 women, 1 man), 25-vitamin D (39.5%, 10 women, 5 men), iron (26.3%, 8 women, 2 men), and zinc (7.9%, 2 women, 1 men). At 3- and 12-month follow-up, no patient in group A had developed new MD, whereas all patients of Group B continued to be deficient in one or more micronutrient, despite systematic postoperative supplementation. No statistical differences (p<0.05) in estimated nutrient intake were observed in either group. Based on our findings, we are able to support the hypothesis that pre-SG correction of MD may be useful in preventing early post-SG MD.