The Efficacy of Energy-Restricted Diets in Achieving Preoperative Weight Loss for Bariatric Patients: a Systematic Review

Effects of GLP-1 receptor agonists on the degree of liver fibrosis and CRP in non-alcoholic fatty liver disease and non-alcoholic steatohepatitis: A systematic review and meta-analysis

BACKGROUND

Based on the rapidly growing global burden of non-alcoholic fatty liver disease (NAFLD) or steatohepatitis (NASH), in order to evaluate the efficacy of glucagon-like peptide-1 receptor agonists (GLP-1RAs) in the treatment of NAFLD or NASH this paper presents a systematic review and meta-analysis of randomized controlled trials(RCTs).

METHODS

In this systematic review and meta-analysis, We searched PubMed, Medline, Web of Science and The Cochrane Library databases. All randomized controlled trials involving GLP-1RAs and NAFLD or NASH were collected since the database was established. A meta-analysis of proportions was done with the generalised linear mixed model. Continuous variables were represented by Mean and Standard Deviation (SD), and binary variable were represented by Relative Risk (RR) and 95% Confidence Interval (CI) as effect indicators. The research results were presented by Revman 5.4. This study is registered with PROSPERO (CRD42023390735).

FINDING

We included 16 placebo-controlled or active drug-controlled randomized controlled trials (involving 2178 patients) that used liraglutide, exenatide, dulaglutide, or semaglutie in the treatment of NAFLD or NASH, as measured by liver biopsy or imaging techniques. This study found that the effect of GLP-1RAs on histologic resolution of NASH with no worsening of liver fibrosis (n=2 RCTs; WMD:4.08, 95%CI 2.54-6.56, p < 0.00001) has statistically significant. At the same time, GLP-1RAs affected CRP (n = 7 RCTs; WMD:-0.41, 95% CI-0.78 to -0.04, p =0.002) and other serological indicators were significantly improved.

CONCLUSION

This study evaluated the efficacy of GLP-1RAs in patients with NAFLD and NASH. These results suggest that GLP-1RAs may be a potential and viable therapeutic approach as a targeted agent to intervene in disease progression of NAFLD and NASH.

Nutrition, Physical Activity, and Prescription of Supplements in Pre- and Post-bariatric Surgery Patients: An Updated Comprehensive Practical Guideline

Only in the USA, 315 billion dollars are spent annually on the medical cost of obesity in adult patients. Till now, bariatric surgery is the most effective method for treating obesity and can play an essential role in reducing the direct and indirect costs of obesity treatment. Nonetheless, there are few comprehensive guidelines which include nutrition, physical activity, and supplements, before and after surgery. The purpose of the present narrative review is to provide an updated and comprehensive practical guideline to help multidisciplinary teams. The core keywords include nutrition, diet, physical activity, exercise, supplements, macronutrients, micronutrients, weight reduction, bariatric surgery, Roux-en-Y Gastric Bypass, Sleeve Gastrostomy, Laparoscopic Adjustable Gastric Banding, and Biliopancreatic diversion with duodenal switch which were searched in databases including PubMed/Medline, Cochrane, and some other sources such as Google Scholar. We answered questions in five important areas: (a) nutritional strategies before bariatric surgery, (b) nutrition after bariatric surgery, (c) physical activity before and after bariatric surgery, (d) weight regain after bariatric surgery, and (e) micronutrient assessments and recommendations before and after bariatric surgery. Some new items were added in this updated guideline including "weight regain" and "pregnancy after bariatric surgery." Other fields were updated based on new evidence and guidelines.

Very low energy diets prior to bariatric surgery may reduce postoperative morbidity: a systematic review and meta-analysis of randomized controlled trials

Purpose

To optimize patients prior to bariatric surgery, very low energy diets (VLEDs) are often employed for 2-4 weeks preoperatively. They are known to result in preoperative weight loss, decrease liver volume, and decrease surgeon-perceived operative difficulty. Their impact on postoperative morbidity has been less extensively studied. We performed a focused systematic review and meta-analysis with the aim of comparing preoperative VLEDs prior to bariatric surgery with controls in terms of overall postoperative morbidity.

Methods

MEDLINE, Embase, and CENTRAL were searched from database inception to February 2023. Articles were eligible for inclusion if they were randomized controlled trials (RCTs) comparing postoperative morbidity in adult patients (i.e., over the age of 18) receiving a VLED with liquid formulation to those receiving a non-VLED control prior to elective bariatric surgery. Outcomes included overall 30-day postoperative morbidity and preoperative weight loss. An inverse variance meta-analysis was performed with GRADE assessment of the quality of evidence.

Results

After reviewing 2,525 citations, four RCTs with 294 patients receiving preoperative VLEDs with liquid formulation and 294 patients receiving a non-VLED control met inclusion. Patients receiving VLED experienced significantly more preoperative weight loss than patients receiving control (mean difference (MD) 3.38 kg, 95% confidence interval (CI) 1.06-5.70, p = 0.004, I² = 95%). According to low certainty evidence, there was a non-significant reduction in 30-day postoperative morbidity in patients receiving VLED prior to bariatric surgery (risk ratio (RR) 0.67, 95%CI 0.39-1.17, p = 0.16, I² = 0%).

Conclusion

The impact of preoperative VLEDs on postoperative outcomes following bariatric surgery remains unclear. It is possible that VLEDs may contribute to decreased postoperative morbidity, but further larger prospective trials are required to investigate the signal identified in this study.

Mechanisms and possible hepatoprotective effects of glucagon-like peptide-1 receptor agonists and other incretin receptor agonists in non-alcoholic fatty liver disease

Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are incretins that stimulate insulin secretion from pancreatic β cells in response to food ingestion. Modified GLP-1 and GIP peptides are potent agonists for their incretin receptors, and some evidence shows that the dual GLP-1 and GIP receptor agonist tirzepatide is effective in promoting marked weight loss. GLP-1 receptor agonists signal in the CNS to suppress appetite, increase satiety, and thereby decrease calorie intake, but many other effects of incretin signalling have been recognised that are relevant to the treatment of non-alcoholic fatty liver disease (NAFLD). This Review provides an overview of the literature supporting the notion that endogenous incretins and incretin-receptor agonist treatments are important not only for decreasing risk of developing NAFLD, but also for treating NAFLD and NAFLD-related complications. We discuss incretin signalling and related incretin-receptor agonist treatments, mechanisms in key relevant tissues affecting liver disease, and clinical data from randomised controlled trials. Finally, we present future perspectives in this rapidly developing field of research and clinical medicine.

Variation and outcomes of liver-reducing dietary regimens before bariatric surgery: a national retrospective cohort study

BACKGROUND

Liver-reducing diets (LRDs) are mandated prior to bariatric surgery, but there are no guidelines on their implementation.

OBJECTIVE

To establish the variation and effectiveness of LRDs utilized in clinical practice.

SETTING

A nationwide, multicenter, retrospective cohort study.

METHODS

A total of 1699 adult patients across 14 bariatric centers in the United Kingdom were included. Multilevel logistic regression models were developed to examine factors predictive of 5% weight loss.

RESULTS

Most centers (n = 9) prescribed an 800- to 1000-kcal diet, but the duration and formulation of diet was variable. Overall, 30.6% (n = 510) of patients achieved 5% weight loss during the LRD. After adjustment for preoperative weight, women had reduced odds (odds ratio [OR], .65; 95% confidence interval [CI], .48-.88; P = .005), while increasing age (OR, 1.01; 95% CI, 1.00-1.02; P = .043) and having type 2 diabetes (OR, 1.49; 95% CI, 1.16-1.92; P = .002) increased odds of 5% weight loss. A normal consistency food LRD (OR, .64; 95% CI, .42-.98; P = .041) and energy prescription of >1200 kcals/d (OR, .33; 95% CI, .13-.83; P = .019) reduced odds, while an LRD with a duration of 3 weeks (OR, 2.28; 95% CI, 1.02-5.09; P = .044) or greater increased odds of 5% weight loss.

CONCLUSIONS

There is wide variation in how LRDs are delivered in clinical practice, highlighting the need for an evidence-based consensus. Our findings suggest the optimal LRD before bariatric surgery contains 800 to 1200 kcals/d over a duration of 3 to 4 weeks. Further research is required to determine the optimal formulation of LRD and whether women may require a lower-energy LRD than men.

Very low energy diets before nonbariatric surgery: A systematic review and meta-analysis

BACKGROUND

Very low energy diets serve as an intensive approach to weight loss in a short period of time. Although the preoperative use of very low energy diets to optimize patients with obesity before bariatric surgery is well established, the evidence for very low energy diets before other types of surgery remains unclear. The aim of this review was to determine the impact of preoperative very low energy diets on perioperative outcomes in nonbariatric surgery.

METHODS

Medline, EMBASE, CENTRAL, and PubMed were systematically searched from inception through to July 2021. Articles were included if they evaluated very low energy diets use before any type of nonbariatric surgery. The primary outcome was postoperative morbidity. Secondary outcomes included compliance, safety, and preoperative weight loss. A pairwise meta-analyses using inverse variance random effects was performed.

RESULTS

From 792 citations, 13 studies with 395 patients (mean age: 56.5 years, 55.8% female) receiving very low energy diets preoperatively in preparation for nonbariatric surgery were included. Mean duration of preoperative very low energy diets was 6.6 weeks (range, 0.42-17 weeks). Target daily caloric intake ranged from 450 kcal to 1,400 kcal. Compliance with very low energy diets ranged from 94% to 100%. The mean preoperative weight loss ranged from 3.2 kg to 19.2 kg. There were no significant differences in postoperative morbidity (odds ratio, 1.10; 95% confidence interval, 0.64-1.91; P = .72), operative time (standard mean difference -0.35; 95% confidence interval, 1.13-0.43, P = .38), or postoperative length of stay (standard mean difference 0.40, 95% confidence interval -0.11-0.91, P = .12) with very low energy diets.

CONCLUSION

Although the currently available evidence is heterogenous, preoperative very low energy diets are safe, well tolerated, and effectively induce preoperative weight loss in patients undergoing nonbariatric surgery for both benign and malignant disease. Further prospective studies are warranted.

Clinical outcomes of single-stage versus two-stage laparoscopic Roux-en-y gastric bypass in the management of obesity (BMI ≥ 50 kg/m2): a retrospective cohort study

BACKGROUND

Laparoscopic Roux-en-Y gastric bypass (LRYGB) in patients with obesity, BMI ≥ 50 kg/m², can be a challenging operation. Weight loss with intra-gastric balloon (IGB) insertion prior to LRYGB may improve operative outcomes.

METHODS

Between June 2000 and June 2020, patients with a BMI ≥ 50 kg/m² underwent either IGB insertion followed by LRYGB (two-stage group), or LRYGB as the definitive bariatric procedure (single-stage group) in our institution. The two-stage procedure was adopted for high risk individuals. Primary outcome measures were percentage total weight loss (%TWL) at 24 months, length of stay and postoperative morbidity. Propensity score analysis was used to account for differences between groups.

RESULTS

A total of 155 (mean age 42.9 years ± 10.60; mean BMI 54.6 kg/m² ± 4.53) underwent either the two-stage (n = 30) or single-stage procedure (n = 125) depending on preoperative fitness. At 6 months following LRYGB, there was a significant difference in %TWL between the groups in a matched analysis (11.9% vs 23.7%, p < 0.001). At 24 months, there was no difference in %TWL (32.0% vs 34.7%, p = 0.13). Median hospital stay following LRYGB was 2.0 (1-4) days with the two-stage vs 2.0 (0-14) days for the single-stage approach (p = 0.75). There was also no significant difference in complication rates (p = 0.058) between the two groups.

CONCLUSIONS

There was no difference in weight loss after one or two-stage procedures in the treatment of patients with a BMI ≥ 50 kg/m² super obesity in a propensity score weighted analysis at 24 months. Length of stay and perioperative complications were similar for high risk patients; however, the two-stage approach was associated with delayed weight loss. Single-stage management is recommended for moderate risk patients, particularly with significant metabolic disorders, whilst two-stage approach is a safe and feasible pathway for high risk individuals.

Effectiveness and Tolerability of a Two-Week Hypocaloric Protein-Rich Diet Prior to Obesity Surgery with Two Different Diet Interventions: a Prospective Randomized Trial

Purpose

Preoperative very low-calorie diets (VLCDs) have been shown to reduce liver volume and improve bariatric surgery safety. Here, we compare two VLCD that differ in macronutrient composition.

Material/Methods

Ninety patients awaiting obesity surgery were included in a prospective, open-label, randomized mono-centre trial comparing the effects of 2-week preoperative VLCDs: BCM Diät™ (diet 1) versus Optifast™ (diet 2).

Results

Data from 33 patients in diet 1 and 36 in diet 2 could be analysed. There was no significant difference between the two diet intervention arms on outcome parameters. Overall, both VLCD strategies led to a mean weight reduction of 5.24 [4.72–5.76] kg (p < 0.001), mean excess weight loss was 8.2 [7.4–9.1] % (p < 0.001). BMI reduction was 1.81 [1.63–1.99] kg/m² (p < 0.001). Over all patients, the liver volume was reduced by 397 [329–466] ml (p < 0.001), which corresponds to 14.6 [12.4; 16.8] %. Liver fat content was significantly reduced by 18.35 [8.98–27.71] %. Reduction of body weight correlates with liver volume loss.

In addition, hip/waist circumferences, body fat and fat-free mass decreased significantly. We found an increase of ALAT/ASAT and a significant decrease of triglycerides, LDL-cholesterol and HbA1c. Parameters of inflammatory were significantly reduced upon VLCD.

Conclusion

Independently of the macronutrient composition, VLCD leads to a significant decrease of body weight, reduction of liver volume and improved parameters of inflammation, glucose and lipid metabolism. Preoperative diets are widely used in conditioning; however, VLCD should be considered as option for patients with obesity undergoing other abdominal surgeries.

Graphical abstract

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.

The relationship between preoperative weight loss and intra and post-bariatric surgery complications: an appraisal of the current preoperative nutritional strategies

Preoperative weight loss before a bariatric surgery reduces long-term complications, but there is no solid evidence for short-term or perioperative complications. This review highlights recent evidence on dietary protocols and the possible correlation between weight loss and surgical complications. Updated evidence was searched in PubMedDirect with the terms "preoperative very low-calorie diet or very-low-calorie ketogenic diet or low-fat diet or intermittent fasting or Mediterranean diet and bariatric surgery or bariatric surgery complications." The main characteristics of each diet, achievements related to weight loss, liver reduction, peri and postoperative outcomes, surgical complications, tolerance, and adherence to the diet are presented from the selected studies. There are few reports about the Mediterranean diet as a strategy to reach these goals. The VLCKD has been associated with better body weight reduction and lesser postoperative complications risk. However, the results in animal models are still controversial. When comparing VLCD with an LCD, there is no apparent superiority between one against the other one. However, LCD has shown better tolerance and adherence than VLCD. There is still a need for more controlled studies to define the best preoperative dietary treatment for weight loss before bariatric surgery since there are controversial positions regarding this issue.

Impact of preoperative weight loss achieved by gastric balloon on peri- and postoperative outcomes of bariatric surgery in super-obese patients: a retrospective matched-pair analysis

Background

An intragastric balloon is used to cause weight loss in super-obese patients (BMI > 60 kg/m²) prior to bariatric surgery. Whether weight loss from intragastric balloon influences that from bariatric surgery is poorly studied.

Methods

In this retrospective, single-center study, the effects of intragastric balloon in 26 patients (BMI 69.26 ± 6.81) on weight loss after bariatric surgery (primary endpoint), postoperative complications within 30 days, hospital readmission, operation time, and MTL30 (secondary endpoints) were evaluated. Fifty-two matched-pair patients without intragastric balloon prior to bariatric surgery were used as controls.

Results

Intragastric balloon resulted in a weight loss of 17.3 ± 14.1 kg (BMI 5.75 ± 4.66 kg/m²) with a nadir after 5 months. Surgical and postoperative outcomes including complications were comparable between both groups. Total weight loss was similar in both groups (29.0% vs. 32.2%, p = 0.362). Direct postoperative weight loss was more pronounced in the control group compared to the gastric balloon group (29.16 ± 7.53% vs 23.78 ± 9.89% after 1 year, p < 0.05 and 32.13 ± 10.5% vs 22.21 ± 10.9% after 2 years, p < 0.05), who experienced an earlier nadir and started to regain weight during the follow-up.

Conclusion

A multi-stage therapeutic approach with gastric balloon prior to bariatric surgery in super-obese patients may be effective to facilitate safe surgery. However, with the gastric balloon, pre-treated patients experienced an attenuated postoperative weight loss with an earlier nadir and earlier body weight regain. This should be considered when choosing the appropriate therapeutic regime and managing patients’ expectations.

Expert opinion on the preoperative medical optimization of adults with diabetes undergoing metabolic surgery

Diabetes mellitus (DM) and obesity are interrelated in a complex manner, and their coexistence predisposes patients to a plethora of medical problems. Metabolic surgery has evolved as a promising therapeutic option for both conditions. It is recommended that patients, particularly those of Asian origin, maintain a lower body mass index threshold in the presence of uncontrolled DM. However, several comorbidities often accompany these chronic diseases and need to be addressed for successful surgical outcome. Laparoscopic Roux-en-Y gastric bypass (RYGB) and laparoscopic sleeve gastrectomy (LSG) are the most commonly used bariatric procedures worldwide. The bariatric benefits of RYGB and LSG are similar, but emerging evidence indicates that RYGB is more effective than LSG in improving glycemic control and induces higher rates of long-term DM remission. Several scoring systems have been formulated that are utilized to predict the chances of remission. A glycemic target of glycated hemoglobin < 7% is a reasonable goal before surgery. Cardiovascular, pulmonary, gastrointestinal, hepatic, renal, endocrine, nutritional, and psychological optimization of surgical candidates improves perioperative and long-term outcomes. Various guidelines for preoperative care of individuals with obesity have been formulated, but very few specifically focus on the concerns arising from the presence of concomitant DM. It is hoped that this statement will lead to the standardization of presurgical management of individuals with DM undergoing metabolic surgery.

Associations of Bariatric Interventions With Micronutrient and Endocrine Disturbances

IMPORTANCE

Few studies have described the longitudinal trajectories of serum levels of micronutrients whose deficiencies are associated with serious sequelae following bariatric procedures, such as anemia, osteoporotic fractures, and neuropathies. Furthermore, previous studies comparing laparoscopic sleeve gastrectomy (LSG) vs Roux-en-Y gastric bypass (LRYGB) or one-anastomosis gastric bypass (OAGB) procedures may have been limited by selection and confounding biases.

OBJECTIVE

To appraise the spectrum and temporal course of micronutrient deficiencies associated with bone metabolism and erythropoiesis after LSG vs OAGB or LRYGB procedures, using the propensity score as a balancing score.

DESIGN, SETTING, AND PARTICIPANTS

This prospective, longitudinal comparative effectiveness study was conducted at a high-volume bariatric unit in Singapore from September 1, 2008, to November 30, 2017, with a cutoff date for analysis of September 2018. Patients who underwent adjustable gastric banding, biliopancreatic diversion procedures, and intragastric balloon procedures were excluded. All other patients who underwent bariatric procedures were included. Data were analyzed from September 23 to 30, 2018.

MAIN OUTCOMES AND MEASURES

Serial assessment of 13 biochemical parameters at 12 time points for up to 5 years after bariatric procedure. Inverse probability-of-treatment weights were used to obtain estimates of the mean associations of variables assessed with the bariatric surgical interventions. Longitudinal trajectories were analyzed using mixed-effects generalized linear models to apportion the temporal variation of serum micronutrients into fixed-effects and random-effects components.

RESULTS

A total of 688 patients were included in this study, of whom 499 underwent LSG (mean [SD] age, 41.5 [11.3] years; 318 [63.7%] women) and 189 underwent OAGB or LRYGB (mean [SD] age, 48.6 [9.4] years; 112 [59.3%] women). There were no differences during follow-up among patients who underwent LSG vs those who underwent OAGB or LRYGB in intact parathyroid hormone levels (mean difference, 7.05 [95% CI, -28.67 to 42.77] pg/mL; P = .70), serum 25-hydroxyvitamin D levels (mean difference, -0.72 [95% CI, -1.56 to 0.12] ng/mL; P = .09), or phosphate levels (mean difference, 0.006 [95% CI, -0.052 to 0.064] mg/dL; P = .83). Hemoglobin levels were a mean 0.63 (95% CI, 0.41 to 0.85) g/dL higher among patients who underwent LSG compared with those who underwent OAGB or LRYGB (P < .001), despite no differences in iron concentration levels (mean difference, 1.50 [95% CI, -1.39 to 4.39] µg/dL; P = .31), total iron-binding capacity (mean difference, 4.36 [95% CI, -5.25 to 13.98] µg/dL; P = .37), or ferritin levels (mean difference, 3.0 [95% CI, -13.0 to 18.9] ng/mL; P = .71). Compared with patients who underwent LSG procedures, patients who underwent OAGB or LRYGB had higher folate levels (mean difference, 2.376 [95% CI, 1.716 to 3.036] ng/mL; P < .001) but lower serum magnesium levels (mean difference, -0.25 [95% CI, -0.35 to -0.16] mg/dL; P < .001) and zinc levels (mean difference, -7.58 [95% CI, -9.92 to -5.24] µg/dL; P < .001).

CONCLUSIONS AND RELEVANCE

These findings suggest that LSG vs OAGB or LRYGB procedures have differential associations with various micronutrient and metabolic parameters. These differences should be recognized in guidelines for postbariatric nutritional surveillance and prevention.

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.