Mechanisms of Weight Loss After Obesity Surgery

The circulating and central endocannabinoid system in obesity and weight loss

Major advances have been made in obesity treatment, focusing on restoring disturbances along the gut-brain axis. The endocannabinoid system (ECS) is a neuromodulatory signaling system, present along the entire gut-brain axis, that plays a critical role in central and peripheral regulation of food intake and body weight. Evidence on the impact of weight loss on the ECS is, however, more limited. Therefore, we set out to review the existing literature for changes in central and circulating endocannabinoid levels after bariatric surgery and other weight loss strategies in humans. The PubMed, Embase and Web of Science databases were searched for relevant articles. Fifty-six human studies were identified. Most studies measuring circulating 2-arachidonoylglycerol (2-AG) found no difference between normal weight and obesity, or no correlation with BMI. In contrast, studies measuring circulating arachidonoylethanolamine (AEA) found an increase or positive correlation with BMI. Two studies found a negative correlation between BMI and cannabinoid receptor type 1 (CB1) receptor availability in the brain. Only one study investigated the effect of pharmacological weight management on circulating endocannabinoid concentrations and found no effect on AEA concentrations. So far, six studies investigated potential changes in circulating endocannabinoids after bariatric surgery and reported conflicting results. Available evidence does not univocally support that circulating endocannabinoids are upregulated in individuals with obesity, which may be explained by variability across studies in several potential confounding factors (e.g. age and sex) as well as heterogeneity within the obesity population (e.g. BMI only vs. intra-abdominal adiposity). While several studies investigated the effect of lifestyle interventions on the circulating ECS, more studies are warranted that focus on pharmacologically and surgically induced weight loss. In addition, we identified several research needs which should be fulfilled to better understand the role of the ECS in obesity and its treatments.

Impact of Gastrojejunostomy Anastomosis Diameter on Weight Loss Following Laparoscopic Gastric Bypass: A Systematic Review

Laparoscopic Roux-en-Y gastric bypass (RYGB) is crucial for significant weight reduction and treating obesity-related issues. However, the impact of gastrojejunostomy (GJ) anastomosis diameter on weight loss remains unclear. We investigate this influence on post-RYGB weight loss outcomes. A systematic search was conducted. Six studies met the inclusion criteria, showing varied GJ diameters and follow-up durations (1-5 years). Smaller GJ diameters generally correlated with greater short-to-medium-term weight loss, with a threshold beyond which complications like stenosis increased. Studies had moderate-to-low bias risk, emphasizing the need for precise GJ area quantification post-operation. This review highlights a negative association between smaller GJ diameters and post-RYGB weight loss, advocating for standardized measurement techniques. Future research should explore intra-operative and AI-driven methods for optimizing GJ diameter determination.

Adaptive thermogenesis, at the level of resting energy expenditure, after diet alone or diet plus bariatric surgery

OBJECTIVE

The objective of this study was to compare the magnitude of adaptive thermogenesis (AT), at the level of resting energy expenditure (REE), after a very low-energy diet alone or combined with Roux-en-Y gastric bypass or sleeve gastrectomy, as well as to investigate the association between AT and changes in appetite.

METHODS

A total of 44 participants with severe obesity underwent 10 weeks of a very low-energy diet alone or combined with Roux-en-Y gastric bypass or sleeve gastrectomy. Body weight and composition, REE, subjective appetite feelings, and plasma concentrations of gastrointestinal hormones were measured at baseline and week 11. AT, at the level of REE, was defined as a significantly lower measured versus predicted (using a regression model with baseline data) REE.

RESULTS

Participants lost 18.4 ± 3.9 kg of body weight and experienced AT, at the level of REE (-121 ± 188 kcal/day; p < 0.001), with no differences among groups. The larger the AT, at the level of REE, the greater the reduction in fasting ghrelin concentrations and the smaller the reduction in feelings of hunger and desire to eat in the postprandial state.

CONCLUSIONS

Weight-loss modality does not seem to modulate the magnitude of AT, at the level of REE. The greater the AT, at the level of REE, the greater the drive to eat following weight loss.

Protein Supplements with Short Peptides Are Better than Complex Protein-Based Supplements on Improving Early Fat-Free Mass Loss Following Bariatric Surgery: A Retrospective Cohort Study

INTRODUCTION

Bariatric surgery (BS) patients are advised to consume protein supplements to prevent fat-free mass (FFM) loss. However, limited research has explored the efficacy of diverse protein presentations on FFM preservation. This study assesses if short peptide-based (SPB) supplements surpass complex protein-based (CPB) supplements in reducing early FFM loss post-surgery.

METHODS

In this retrospective cohort study, 138 patients who underwent BS other than Roux-en-Y-gastric bypass (RYGB) between January 2021 and March 2021 at the Department of Bariatric Surgery of the Third People's Hospital of Chengdu were included for analysis. Patients were divided into two groups based on their consumption of protein supplements after surgery: SPB group and CPB group. Multiple linear regressions separated by sex were employed to examine the associations between SPB supplements and FFM loss and percentage of FFM (%FFM) loss, respectively.

RESULTS

Among participants, 69.6% were female, with a mean age of 33.3 years. In multiple linear regression analyses, SPB supplements were significantly and positively associated with a lower FFM loss in both female (ꞵ =  - 1.14, P = 0.047) and male (ꞵ =  - 2.36, P = 0.024), and were positively associated with a lower %FFM loss in both female (ꞵ =  - 1.83) and male (ꞵ =  - 2.26) but only significant in male (P = 0.049).

CONCLUSION

SPB supplements may be more effective in preventing early FFM loss after BS, compared to CPB supplements, particularly among male patients. Therefore, SPB supplements may be recommended to patients undergoing BS. Further research is needed to validate these findings.

The risk and benefit of revisional vs. primary metabolic- bariatric surgery and drug therapy - A narrative review

Metabolic and bariatric surgery (MBS) leads to long-term weight loss, reduced risk of cardiovascular events and cancer, and reduced mortality. Sleeve gastrectomy and Roux-en-Y gastric bypass are currently the most common surgical techniques. Weight loss after MBS was previously believed to work through restriction and malabsorption, however, mechanistic studies show that MBS techniques with long term efficacy instead alter physiological signaling between the gut and the brain. In revisional MBS, the initial surgical technique is corrected, modified, or converted to a new one. The indication for revisional MBS can be to achieve further weight loss or improvement in obesity comorbidity, but it may be necessary due to complications (e.g., gastroesophageal reflux or obstruction). Revisional MBS is associated with an increased risk of surgical complications and often less weight loss compared to the results following primary surgery. This narrative review summarizes data from revisional MBS where information is often presented with inconsistent definitions for indications and outcomes, making comparison between strategies difficult. In summary, we suggest careful weighing of potential benefits and risks with revisional MBS, bearing in mind the option of add-on therapy with new anti-obesity drugs.

Characteristics of changes in plasma proteome profiling after sleeve gastrectomy

Bariatric surgery (BS), recognized as the most effective intervention for morbid obesity and associated metabolic comorbidities, encompasses both weight loss-dependent and weight loss-independent mechanisms to exert its metabolic benefits. In this study, we employed plasma proteomics technology, a recently developed mass spectrometric approach, to quantitatively assess 632 circulating proteins in a longitudinal cohort of 9 individuals who underwent sleeve gastrectomy (SG). Through time series clustering and Gene Ontology (GO) enrichment analysis, we observed that complement activation, proteolysis, and negative regulation of triglyceride catabolic process were the primary biological processes enriched in down-regulated proteins. Conversely, up-regulated differentially expressed proteins (DEPs) were significantly associated with negative regulation of peptidase activity, fibrinolysis, keratinocyte migration, and acute-phase response. Notably, we identified seven proteins (ApoD, BCHE, CNDP1, AFM, ITIH3, SERPINF1, FCN3) that demonstrated significant alterations at 1-, 3-, and 6-month intervals post SG, compared to baseline. These proteins play essential roles in metabolism, immune and inflammatory responses, as well as oxidative stress. Consequently, they hold promising potential as therapeutic targets for combating obesity and its associated comorbidities.

Bariatric Surgery in Women with Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrine condition in premenopausal women and is a common cause of anovulatory subfertility. Although obesity does not form part of the diagnostic criteria, it affects a significant proportion of women with PCOS and is strongly implicated in the pathophysiology of the disease. Both PCOS and obesity are known to impact fertility in women; obesity also reduces the success of assisted reproductive technology (ART). With or without pharmacotherapy, lifestyle intervention remains the first-line treatment in women with PCOS and obesity. Bariatric surgery is still an experimental treatment in women with PCOS and subfertility. This review will present an overview of the pathophysiology of PCOS and obesity and the role of bariatric surgery. Although data are sparse regarding the impact of bariatric surgery on subfertility in women with PCOS and obesity, existing studies point to a beneficial role in treating metabolic and reproductive dysfunction.

The Road towards Triple Agonists: Glucagon-Like Peptide 1, Glucose-Dependent Insulinotropic Polypeptide and Glucagon Receptor - An Update

Obesity is the fifth leading risk factor for global deaths with numbers continuing to increase worldwide. In the last 20 years, the emergence of pharmacological treatments for obesity based on gastrointestinal hormones has transformed the therapeutic landscape. The successful development of glucagon-like peptide-1 (GLP-1) receptor agonists, followed by the synergistic combined effect of glucose-dependent insulinotropic polypeptide (GIP)/GLP-1 receptor agonists achieved remarkable weight loss and glycemic control in those with the diseases of obesity and type 2 diabetes. The multiple cardiometabolic benefits include improving glycemic control, lipid profiles, blood pressure, inflammation, and hepatic steatosis. The 2023 phase 2 double-blind, randomized controlled trial evaluating a GLP-1/GIP/glucagon receptor triagonist (retatrutide) in patients with the disease of obesity reported 24.2% weight loss at 48 weeks with 12 mg retatrutide. This review evaluates the current available evidence for GLP-1 receptor agonists, dual GLP-1/GIP receptor co-agonists with a focus on GLP-1/GIP/glucagon receptor triagonists and discusses the potential future benefits and research directions.

Gut microbiota changes associated with low-carbohydrate diet intervention for obesity

Low-carbohydrate diets (LCDs) are frequently recommended for alleviating obesity, and the gut microbiota plays key roles in energy metabolism and weight loss. However, there is limited in-human research on how LCD changes gut microbiota. In this before-after study, 43 participants were assigned to the LCD intervention for 4 weeks. The main objective was to investigate the specific changes that occur in the participants' microbiome in response to the LCD. Changes in gut microbiota were analyzed using 16s rRNA sequencing. Body composition was measured using InBody 770. Remarkably, 35 participants (79.07%) lost more than 5% of their body weight; levels of BMI, body fat, and total cholesterol were significantly decreased, indicating the effectiveness of the LCD intervention. The richness of microbiota significantly increased after the intervention. By taking the intersection of ANOVA and linear discriminant analysis effect size (LEfSe) analysis results, we identified three phyla, three classes, four orders, five families, and six genera that were differentially enriched between baseline and week-4 time points. Among the three phyla, relative abundances of Firmicutes and Actinobacteriota decreased significantly, while Bacteroidetes increased significantly. At the genus level, Ruminococcus, Agathobacter, Streptococcus, and Bifidobacterium showed a significant reduction in relative abundances, whereas Parabacteroides and Bacteroides increased steadily. Our results demonstrate that LCD can effectively alleviate obesity and modify certain taxa of gut microbiota, providing potential insights for personalized dietary interventions against obesity.

Obesity surgery and neural correlates of human eating behaviour: A systematic review of functional MRI studies

Changes in eating behaviour including reductions in appetite and food intake, and healthier food cue reactivity, reward, hedonics and potentially also preference, contribute to weight loss and its health benefits after obesity surgery. Functional magnetic resonance imaging (fMRI) has been increasingly used to interrogate the neural correlates of eating behaviour in obesity, including brain reward-cognitive systems, changes after obesity surgery, and links with alterations in the gut-hormone-brain axis. Neural responses to food cues can be measured by changes in blood oxygen level dependent (BOLD) signal in brain regions involved in reward processing, including caudate, putamen, nucleus accumbens, insula, amygdala, orbitofrontal cortex, and top-down inhibitory control, including dorsolateral prefrontal cortex (dlPFC). This systematic review aimed to examine: (i) results of human fMRI studies involving obesity surgery, (ii) important methodological differences in study design across studies, and (iii) correlations and associations of fMRI findings with clinical outcomes, other eating behaviour measures and mechanistic measures. Of 741 articles identified, 23 were eligible for inclusion: 16 (69.6%) longitudinal, two (8.7%) predictive, and five (21.7%) cross-sectional studies. Seventeen studies (77.3%) included patients having Roux-en-Y gastric bypass (RYGB) surgery, six (26.1%) vertical sleeve gastrectomy (VSG), and five (21.7%) laparoscopic adjustable gastric banding (LAGB). The majority of studies (86.0%) were identified as having a very low risk of bias, though only six (27.3%) were controlled interventional studies, with none including randomisation to surgical and control interventions. The remaining studies (14.0%) had a low risk of bias driven by their control groups not having an active treatment. After RYGB surgery, food cue reactivity often decreased or was unchanged in brain reward systems, and there were inconsistent findings as to whether reductions in food cue reactivity was greater for high-energy than low-energy foods. There was minimal evidence from studies of VSG and LAGB surgeries for changes in food cue reactivity in brain reward systems, though effects of VSG surgery on food cue reactivity in the dlPFC were more consistently found. There was consistent evidence for post-operative increases in satiety gut hormones glucagon-like-peptide 1 (GLP-1) and peptide YY (PYY) mediating reduced food cue reactivity after RYGB surgery, including two interventional studies. Methodological heterogeneity across studies, including nutritional state, nature of food cues, post-operative timing, lack of control groups for order effects and weight loss or dietary/psychological advice, and often small sample sizes, limited the conclusions that could be drawn, especially for correlational analyses with clinical outcomes, other eating behaviour measures and potential mediators. This systematic review provides a detailed data resource for those performing or analysing fMRI studies of obesity surgery and makes suggestions to help improve reporting and design of such studies, as well as future directions.

Body Fat Depletion: the Yin Paradigm for Treating Type 2 Diabetes

PURPOSE OF REVIEW

To highlight that body fat depletion (the Yin paradigm) with glucose-lowering treatments (the Yang paradigm) are associated with metabolic benefits for patients with type 2 diabetes mellitus (T2DM).

RECENT FINDINGS

The sodium-glucose cotransporter-2 inhibitor-mediated sodium/glucose deprivation can directly improve glycemic control and kidney outcome in patients with T2DM. The glucose deprivation might also promote systemic fatty acid β-oxidation to deplete ectopic/visceral fat and thereby contribute to the prevention of cardiovascular diseases. As with metabolic surgery, bioengineered incretin-based medications with potent anorexigenic and insulinotropic efficacy can significantly reduce blood glucose as well as body weight (especially in the ectopic/visceral fat depots). The latter effects could be a key contributor to their cardiovascular-renal protective effects. In addition to a healthy diet, the newer glucose-lowering medications, with body fat reduction effects, should be prioritized when treating patients with T2DM, especially for those with established cardiovascular/renal risks or diseases.

Effect of Bariatric Surgery on Gut Microbiota: A Scientometric Analysis

Objective

To perform a bibliometric analysis of the scientific production related to intestinal microbiota and bariatric surgery between January 2016 and December 2022.

Materials and Methods

A bibliographic search was performed in the Scopus database to identify published papers. Free and controlled terms (MeSH and Emtree) were used. The information collected was analyzed with SciVal.

Results

A total of 518 published papers were included in the analysis. Carel Le Roux was the author with the highest scientific production; however, Edi Prifti had the highest impact. French National Institute of Health and Medical Research (Institut national de la santé et de la recherche médicale) was the institution with the highest number of published articles. Six of the 10 institutions with the highest production were in France, yet the United States had the highest volume of scientific production in this research topic. Most papers were published in first quartile journals. Articles with international collaboration had the highest impact. There is a sustained increase in the number of publications since 2019.

Conclusions

The study found that the vast majority of research on gut microbiota changes following bariatric surgery are conducted in the United States and European countries. In addition, the sustained increase in production coupled with the articles being published in high-quality journals and having good citation impact are indictors of the current interest in this research field.

Development and complications of nutritional deficiencies after bariatric surgery

The clinical effectiveness of bariatric surgery has encouraged the use of bariatric procedures for the treatment of morbid obesity and its comorbidities, with sleeve gastrectomy and Roux-en-Y gastric bypass being the most common procedures. Notwithstanding its success, bariatric procedures are recognised to predispose the development of nutritional deficiencies. A framework is proposed that provides clarity regarding the immediate role of diet, the gastrointestinal tract and the medical state of the patient in the development of nutritional deficiencies after bariatric surgery, while highlighting different enabling resources that may contribute. Untreated, these nutritional deficiencies can progress in the short term into haematological, muscular and neurological complications and in the long term into skeletal complications. In this review, we explore the development of nutritional deficiencies after bariatric surgery through a newly developed conceptual framework. An in-depth understanding will enable the optimisation of the post-operative follow-up, including detecting clinical signs of complications, screening for laboratory abnormalities and treating nutritional deficiencies.

Preoperative Weight Gain Is Not Related to Lower Postoperative Weight Loss, But to Lower Total Weight Loss up to 3 Years After Bariatric-Metabolic Surgery

INTRODUCTION

Weight loss prior to bariatric-metabolic surgery (BMS) is recommended in most bariatric centers. However, there is limited high-quality evidence to support mandatory preoperative weight loss. In this study, we will evaluate whether weight gain prior to primary BMS is related to lower postoperative weight loss.

METHODS

A retrospective analysis of prospectively collected data was performed. Preoperative weight loss (weight loss from start of program to day of surgery), postoperative weight loss (weight loss from day of surgery to follow-up), and total weight loss (weight loss from start of program to follow-up) were calculated. Five groups were defined based on patients' preoperative weight change: preoperative weight loss of >5 kg (group I), 3-5 kg (group II), 1-3 kg (group III), preoperative stable weight (group IV), and preoperative weight gain >1 kg (group V). Linear mixed models were used to compare the postoperative weight loss between group V and the other four groups (I-IV).

RESULTS

A total of 1928 patients were included. Mean age was 44 years, 78.6% were female, and preoperative BMI was 43.7 kg/m2. Analysis showed significantly higher postoperative weight loss in group V, compared to all other groups at 12, 24, and 36 months follow-up. Up to three years follow-up, highest total weight loss was observed in group I.

CONCLUSION

Weight gain before surgery should not be a reason to withhold a bariatric-metabolic operation. However, patients with higher preoperative weight loss have higher total weight loss. Therefore, preoperative weight loss should be encouraged prior to bariatric surgery.

New insights in the mechanisms of weight-loss maintenance: Summary from a Pennington symposium

Obesity is a chronic disease that affects more than 650 million adults worldwide. Obesity not only is a significant health concern on its own, but predisposes to cardiometabolic comorbidities, including coronary heart disease, dyslipidemia, hypertension, type 2 diabetes, and some cancers. Lifestyle interventions effectively promote weight loss of 5% to 10%, and pharmacological and surgical interventions even more, with some novel approved drugs inducing up to an average of 25% weight loss. Yet, maintaining weight loss over the long-term remains extremely challenging, and subsequent weight gain is typical. The mechanisms underlying weight regain remain to be fully elucidated. The purpose of this Pennington Biomedical Scientific Symposium was to review and highlight the complex interplay between the physiological, behavioral, and environmental systems controlling energy intake and expenditure. Each of these contributions were further discussed in the context of weight-loss maintenance, and systems-level viewpoints were highlighted to interpret gaps in current approaches. The invited speakers built upon the science of obesity and weight loss to collectively propose future research directions that will aid in revealing the complicated mechanisms involved in the weight-reduced state.

Bariatric surgery alters mitochondrial function in gut mucosa

BACKGROUND

The obesity pandemic has worsened global disease burden, including type 2 diabetes, cardiovascular disease, and cancer. Metabolic/bariatric surgery (MBS) is the most effective and durable obesity treatment, but the mechanisms underlying its long-term weight loss efficacy remain unclear. MBS drives substrate oxidation that has been linked to improvements in metabolic function and improved glycemic control that are potentially mediated by mitochondria-a primary site of energy production. As such, augmentation of intestinal mitochondrial function may drive processes underlying the systemic metabolic benefits of MBS. Herein, we applied a highly sensitive technique to evaluate intestinal mitochondrial function ex vivo in a mouse model of MBS.

METHODS

Mice were randomized to surgery, sham, or non-operative control. A simplified model of MBS, ileal interposition, was performed by interposition of a 2-cm segment of terminal ileum into the proximal bowel 5 mm from the ligament of Treitz. After a four-week recovery period, intestinal mucosa of duodenum, jejunum, ileum, and interposed ileum were assayed for determination of mitochondrial respiratory function. Citrate synthase activity was measured as a marker of mitochondrial content.

RESULTS

Ileal interposition was well tolerated and associated with modest body weight loss and transient hypophagia relative to controls. Mitochondrial capacity declined in the native duodenum and jejunum of animals following ileal interposition relative to controls, although respiration remained unchanged in these segments. Similarly, ileal interposition lowered citrate synthase activity in the duodenum and jejunum following relative to controls but ileal function remained constant across all groups.

CONCLUSION

Ileal interposition decreases mitochondrial volume in the proximal intestinal mucosa of mice. This change in concentration with preserved respiration suggests a global mucosal response to segment specific nutrition signals in the distal bowel. Future studies are required to understand the causes underlying these mitochondrial changes.

Effect of bariatric surgery on cardio-psycho-metabolic outcomes in severe obesity: A randomized controlled trial

OBJECTIVE

Randomized evidence comparing the cardiovascular effects of surgical and conservative weight management is lacking.

PATIENTS & METHODS

In this single-center, open-label randomized trial, obese patients with indication for Roux-en-Y gastric bypass (RYGB) and able to perform treadmill cardiopulmonary exercise testing (CPET) were included. After a 6-12 month run-in phase of multimodal anti-obesity treatment, patients were randomized to RYGB or psychotherapy-enhanced lifestyle intervention (PELI) and co-primary endpoints were assessed 12 months later. Thereafter, PELI patients could opt for surgery and patients were reassessed 24 months after randomization. Co-primary endpoints were mean change (95 % confidence intervals) in peak VO2 (ml/min/kg body weight) in CPET and the physical functioning scale (PFS) of the Short Form health survey (SF-36).

RESULTS

Of 93 patients entering the study, 60 were randomized. Among these (median age 38 years; 88 % women; mean BMI 48·2 kg/m2), 46 (RYGB: 22 and PELI: 24) were evaluated after 12 months. Total weight loss was 34·3 % after RYGB vs. 1·2 % with PELI, while peak VO2 increased by +4·3 ml/min/kg (2·7, 5·9) vs +1·1 ml/min/kg (-0·2, 2·3); p < 0·0001. Respective improvement in PFS score was +40 (30, 49) vs +10 (1, 15); p < 0·0001. 6-minute walking distance also favored the RYGB group: +44 m (17, 72) vs +6 m (-14, 26); p < 0·0001. Left ventricular mass decreased after RYGB, but not with PELI: -32 g (-46, -17) vs 0 g (-13,13); p < 0·0001. In the non-randomized follow-up, 34 patients were assessed. Favorable changes were sustained in the RYGB group and were repeated in the 15 evaluated patients that opted for surgery after PELI.

CONCLUSIONS

Among adults with severe obesity, RYGB in comparison to PELI resulted in improved cardiopulmonary capacity and quality of life. The observed effect sizes suggest that these changes are clinically relevant.

Weight loss to disrupt type 2 diabetes

Obesity is now recognised as a disease associated with significant morbidity and mortality. One of the most common metabolic complications of obesity is type 2 diabetes, because the two disease share similar pathophysiology. Weight loss is known to ameliorate the metabolic abnormalities underlying type 2 diabetes and improve glycemic control. A 15% or greater total body weight loss (TBWL) in patients with type 2 diabetes will have a disease-modifying effect, a result that is incomparable with other hypoglycemic-lowering interventions. Moreover, in patients with diabetes and obesity, weight loss exerts benefits beyond glycemic control and improves cardiometabolic disease risk factors and well-being. We review evidence supporting the role of intentional weight loss in managing type 2 diabetes. We suggest that many people with type 2 diabetes would benefit from an additional weight-based approach to managing their diabetes. Therefore, we proposed a weight-based treatment goal for patients with type 2 diabetes and obesity.

Distinct adaptations of endocrine and cognitive functions may contribute to high variability in long-term weight loss outcome after bariatric surgery

BACKGROUND

Bariatric surgery has been widely recognized as the most efficient long-term treatment method in severe obesity, yet therapy success shows considerable interindividual variability. Postoperative metabolic adaptations, including improved gut hormone secretion (GLP-1, PYY and ghrelin), and restored executive function may play an explanatory role in weight loss, yet causes for poor success in individual patients remain unknown. This study investigates gut-hormonal and cognitive characteristics in extreme weight loss responders to bariatric surgery.

METHODS

Patients (n=47) with high or low excessive weight loss (EWL) at least 2 years after Roux-en-Y-gastric bypass or sleeve gastrectomy were allocated into good responders (GR, EWL 82.4 ± 11.6%) and poor responders (PR, EWL 24.0 ± SD 12.8%) to study differences in postprandial secretion of GLP-1, PYY, ghrelin and in working memory (WM).

RESULTS

Mean BMI was 47.1 ± 6.2 kg/m² in PR (n=21) and 28.9 ± 3.1 kg/m² in GR (n=26, p < 0.001). Fasted GLP-1 and PYY were comparable for GR and PR (p > 0.2) and increased strongly after a standardized test meal (300 kcal liquid meal) with a peak at 15 to 30 minutes. The increase was stronger in GR compared to PR (GLP-1, PYY: Time x Group p < 0.05). Plasma ghrelin levels already differed between groups at fasted state, showing significantly higher levels for GR (p < 0.05). Postprandially, ghrelin secretion was suppressed in both groups, but suppression was higher in GR (Time x Group p < 0.05). GR showed significantly higher WM scores than PR (p < 0.05). Postprandial ghrelin (iAUC), but not GLP-1 or PYY plasma levels, significantly mediated the relationship between EWL and a WM subscore (IS score, CI = 0.07 - 1.68), but not WM main score (MIS score, CI = -0.07 - 1.54), in mediation analyses.

CONCLUSION

Excess weight loss success after bariatric surgical procedures is associated with distinct profiles of gut-hormones at fasted and postprandial state, and differences in working memory. Better working memory performance in GR might be mediated by higher postprandial reduction in ghrelin plasma levels. Future studies need to integrate longitudinal data, larger samples and more sensitive cognitive tests.

Gut hormone co-agonists for the treatment of obesity: from bench to bedside

The discovery and development of so-called gut hormone co-agonists as a new class of drugs for the treatment of diabetes and obesity is considered a transformative breakthrough in the field. Combining action profiles of multiple gastrointestinal hormones within a single molecule, these novel therapeutics achieve synergistic metabolic benefits. The first such compound, reported in 2009, was based on balanced co-agonism at glucagon and glucagon-like peptide-1 (GLP-1) receptors. Today, several classes of gut hormone co-agonists are in development and advancing through clinical trials, including dual GLP-1-glucose-dependent insulinotropic polypeptide (GIP) co-agonists (first described in 2013), and triple GIP-GLP-1-glucagon co-agonists (initially designed in 2015). The GLP-1-GIP co-agonist tirzepatide was approved in 2022 by the US Food and Drug Administration for the treatment of type 2 diabetes, providing superior HbA1c reductions compared to basal insulin or selective GLP-1 receptor agonists. Tirzepatide also achieved unprecedented weight loss of up to 22.5%-similar to results achieved with some types of bariatric surgery-in non-diabetic individuals with obesity. In this Perspective, we summarize the discovery, development, mechanisms of action and clinical efficacy of the different types of gut hormone co-agonists, and discuss potential challenges, limitations and future developments.

Obesity wars: hypothalamic sEVs a new hope

There are currently several pharmacological therapies available for the treatment of obesity, targeting both the central nervous system (CNS) and peripheral tissues. In recent years, small extracellular vesicles (sEVs) have been shown to be involved in many pathophysiological conditions. Because of their special nanosized structure and contents, sEVs can activate receptors and trigger intracellular pathways in recipient cells. Notably, in addition to transferring molecules between cells, sEVs can also alter their phenotypic characteristics. The purpose of this review is to discuss how sEVs can be used as a CNS-targeted strategy for treating obesity. Furthermore, we will evaluate current findings, such as the sEV-mediated targeting of hypothalamic AMP-activated protein kinase (AMPK), and discuss how they can be translated into clinical application.

Effects of Heterozygous Variants in the Leptin-Melanocortin Pathway on Transoral Outlet Reduction After Roux-en-Y Gastric Bypass: A Case-Control Study and Review of Literature

BACKGROUND

Transoral outlet reduction (TORe) is a safe and effective technique for management of weight regain (WR) after Roux-en-Y Gastric Bypass (RYGB). Carriers of a heterozygous variant in the leptin melanocortin pathway (LMP) have been shown to be at high risk for WR in the mid- and long-term after RYGB. Our case series includes four patients with heterozygous LMP variants and presents novel data on their weight loss after TORe.

METHODS

We performed a retrospective study of the Mayo Clinic Biobank and identified adult participants who had been genotyped and found to have or do not have a heterozygous variant in the LMP ("carriers" vs "non-carriers", respectively) and had undergone a TORe procedure. TBWL% at 1, 3, 6, 9, and 12 months ± 15 days were calculated based on baseline weight at TORe procedure.

RESULTS

A total of 14 patients were included in the analysis: four patients (mean age 51.0 [5.2] years, 100% females, body mass index [BMI] 40.5 [8.7] kg/m²) with LMP variant and 10 non-carriers (age 55.4 [15.3] years, 90% females, BMI 37.3 [7.7] kg/m²). There were no baseline differences between carriers and non-carriers at time of TORe procedure. After TORE, carriers lost less weight when compared to non-carriers at 3, 6, 9, and 12 months. The difference at 12 months was statistically significant (1.6 vs 12.3%; p = 0.03).

CONCLUSIONS

Patients with a LMP variant and that underwent RYGB showed decreased weight loss after undergoing TORe. Further and larger studies are needed to comprehend the effect of TORe on patients with LMP variants.

The Black Box Orchestra of Gut Bacteria and Bile Acids: Who Is the Conductor?

Over the past decades the potential role of the gut microbiome and bile acids in type 2 diabetes mellitus (T2DM) has been revealed, with a special reference to low bacterial alpha diversity. Certain bile acid effects on gut bacteria concern cytotoxicity, or in the case of the microbiome, bacteriotoxicity. Reciprocally, the gut microbiome plays a key role in regulating the bile acid pool by influencing the conversion and (de)conjugation of primary bile acids into secondary bile acids. Three main groups of bacterial enzymes responsible for the conversion of bile acids are bile salt hydrolases (BSHs), hydroxysteroid dehydrogenases (HSDHs) and enzymes encoded in the bile acid inducible (Bai) operon genes. Interventions such as probiotics, antibiotics and fecal microbiome transplantation can impact bile acids levels. Further evidence of the reciprocal interaction between gut microbiota and bile acids comes from a multitude of nutritional interventions including macronutrients, fibers, prebiotics, specific individual products or diets. Finally, anatomical changes after bariatric surgery are important because of their metabolic effects. The heterogeneity of studies, diseases, bacterial species and (epi)genetic influences such as nutrition may challenge establishing specific and detailed interventions that aim to tackle the gut microbiome and bile acids.

Short-term Weight Trajectory of Severely Obese Individuals With and Without Pathogenic Satiety-Regulation Melanocortin 3/4 Receptor (MC3/4R) Mutations From a Multi-ethnic Asian Large Bariatric Surgery Program

The melanocortin (3 or 4) receptor (MC3/4R) is involved in regulating satiety and body weight. Therefore, pathogenic mutation in MC3/4R is associated with severe obesity, for which bariatric surgery is one of the treatment options. However, there is limited data on whether individuals with MC3/4R mutation will have differential weight response to surgery, especially among the Asian populations-the epi-center of the evolving global obesity epidemic. From our large prospective Obesity-Metabolism & Intervention Cohort Study (OMICS; N = 654, recruited between 2007 and 2022), 5 individuals with pathogenic MC3/4R mutations ("case") were identified using candidate-genes panel next-generation sequencing (Illumina iSeq). These subjects were carefully propensity score-matched (baseline body mass index [BMI], age, sex, ethnicity, proportion with diabetes, type of bariatric surgery) in a 1:4 ratio to other controls. We performed linear mixed model analysis (for repeated measurements) to compare their longitudinal weight trajectories (percentage total weight loss, %TWL) over 12 months. The 5 cases with MC3/4R mutations were 48 ± 11 years, BMI 40.8 ± 11.2 kg/m2, 60% with diabetes, and all males. Their weight at baseline (pre-op), and 6 months and 12 months after surgery were 120 ± 38, 100 ± 31, and 101 ± 30 kg, respectively. Compared with propensity score-matched controls (N = 20), linear mixed model analysis suggested no difference in surgically induced %TWL (β coefficient = -5.8 ± 3.7, P = .13) over 12 months between the groups. Therefore, we conclude that rare pathogenic MC3/4R mutations do not significantly modify weight change (%TWL) in response to bariatric surgery.

Hypothalamic integrity is necessary for sustained weight loss after bariatric surgery: A prospective, cross-sectional study

OBJECTIVE

The hypothalamus is the main integrator of peripheral and central signals in the control of energy homeostasis. Its functional relevance for the effectivity of bariatric surgery is not entirely elucidated. Studying the effects of bariatric surgery in patients with hypothalamic damage might provide insight.

SUMMARY BACKGROUND DATA

Prospective study to analyze the effects of bariatric surgery in patients with hypothalamic obesity (HO) vs. matched patients with common obesity (CO) with and without bariatric surgery.

METHODS

65 participants were included (HO-surgery: n = 8, HO-control: n = 10, CO-surgery: n = 12, CO-control: n = 12, Lean-control: n = 23). Body weight, levels of anorexic hormones, gut microbiota, as well as subjective well-being/health status, eating behavior, and brain activity (via functional MRI) were evaluated.

RESULTS

Patients with HO lost significantly less weight after bariatric surgery than CO-participants (total body weight loss %: 5.5 % vs. 26.2 %, p = 0.0004). After a mixed meal, satiety and abdominal fullness tended to be lowest in HO-surgery and did not correlate with levels of GLP-1 or PYY. Levels of PYY (11,151 ± 1667 pmol/l/h vs. 8099 ± 1235 pmol/l/h, p = 0.028) and GLP-1 (20,975 ± 2893 pmol/l/h vs. 13,060 ± 2357 pmol/l/h, p = 0.009) were significantly higher in the HO-surgery vs. CO-surgery group. Abundance of Enterobacteriaceae and Streptococcus was increased in feces of HO and CO after bariatric surgery. Comparing HO patients with lean-controls revealed an increased activation in insula and cerebellum to viewing high-caloric foods in left insula and cerebellum in fMRI.

CONCLUSIONS

Hypothalamic integrity is necessary for the effectiveness of bariatric surgery in humans. Peripheral changes after bariatric surgery are not sufficient to induce satiety and long-term weight loss in patients with hypothalamic damage.

Effects of Lifestyle and Educational Bridging Programs before Bariatric Surgery on Postoperative Weight Loss: A Systematic Review and Meta-Analysis

OBJECTIVE

To fulfill the requirements for bariatric surgery, patients often need to participate in mandatory preoperative lifestyle interventions. Currently, the efficacy of multi-month preoperative lifestyle intervention programs on body mass index (BMI) reduction from the start of the program (T0) through the immediate preoperative time point (T1) to 1 year post-surgery (T2) and how the amount of preoperative BMI reduction affects postoperative outcome (T1 to T2) is unclear. The aim of this meta-analysis was to analyze the effects of preoperative lifestyle interventions on BMI 1 year post-surgery.

METHOD

A systematic literature search was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses criteria. Randomized controlled trials that implemented preoperative lifestyle interventions lasting 1-8 months before bariatric surgery were included. The BMI of the intervention group was compared with that of a control group before participation in the preoperative lifestyle interventions (T0), after completion of the program before surgery (T1), and 1 year post-surgery (T2). Finally, the impact of successful BMI reduction at T1 on BMI at T2 was analyzed.

RESULTS

N = 345 patients derived from 4 studies undergoing preoperative lifestyle interventions reduced their BMI at T1 by 1.5 units compared to the control group (95% CI: -2.73, -0.28). One year post-surgery, both groups had lost comparable BMI points. The influence of reduced BMI at T1 on weight status at T2 is unclear due to the lack of available studies. Other endpoints and subgroup analyses were rarely examined.

CONCLUSIONS

Preoperative lifestyle interventions reduce BMI before bariatric surgery more effectively than usual care. These differences are not detectable 1 year post-surgery. Although a short-term energy reduction period before surgery is clearly important to minimize surgery risks, it is currently unclear whether, and if so, under what circumstances, participation in a preoperative lifestyle intervention is beneficial.

Delayed Gastric Emptying After Sleeve Gastrectomy Is Associated with Poor Weight Loss

Background

Intermediate to long-term weight regain is a major challenge following sleeve gastrectomy (SG). Physiological changes that mediate the extent of weight loss remain unclear. We aimed to determine if there were specific esophago-gastric transit and emptying alterations associated with weight regain.

Material and Methods

Participants greater than 12 months post-SG were categorized into optimal (n = 29) and poor weight loss (PWL) (n = 72). All patients underwent a liquid contrast barium swallow demonstrating normal post-surgical anatomy and a protocolized nuclear scintigraphy designed specifically to characterize gastric emptying following SG.

Results

The %total weight loss in the optimal group was 26.2 ± 10.5 vs. 14.3 ± 8.8% in the PWL group (p = 0.001). Scintigraphy showed PWL had relatively increased gastric emptying half-time (GE 1/2t) 35 (IQR 23) min vs 19 (IQR 5.5) min (p = 0.001). The multivariate regressions delineated GE 1/2t as the best diagnostic measure for PWL (OR 1.16; CI 1.04–1.29, p-value 0.021). The probability of PWL increased by 16% for every 1-min increase above 21 min of GE 1/2t. A threshold of 21 min was found to have 88% sensitivity and 69% specificity predicting poor weight loss.

Conclusion

Gastric emptying half-times greater than 21 min appear to reliably correlate with poor weight loss following SG. Additionally, further elevations above 21 min in emptying half-time increase the risk of poor weight loss. We have shown nuclear scintigraphy represents a simple and accurate diagnostic tool in patients who experience poor weight loss after SG, provided substantially altered reporting references in interpreting nuclear scintigraphy are applied.

Graphical abstract

Data assimilation on mechanistic models of glucose metabolism predicts glycemic states in adolescents following bariatric surgery

Type 2 diabetes mellitus is a complex and under-treated disorder closely intertwined with obesity. Adolescents with severe obesity and type 2 diabetes have a more aggressive disease compared to adults, with a rapid decline in pancreatic β cell function and increased incidence of comorbidities. Given the relative paucity of pharmacotherapies, bariatric surgery has become increasingly used as a therapeutic option. However, subsets of this population have sub-optimal outcomes with either inadequate weight loss or little improvement in disease. Predicting which patients will benefit from surgery is a difficult task and detailed physiological characteristics of patients who do not respond to treatment are generally unknown. Identifying physiological predictors of surgical response therefore has the potential to reveal both novel phenotypes of disease as well as therapeutic targets. We leverage data assimilation paired with mechanistic models of glucose metabolism to estimate pre-operative physiological states of bariatric surgery patients, thereby identifying latent phenotypes of impaired glucose metabolism. Specifically, maximal insulin secretion capacity, σ, and insulin sensitivity, S_I, differentiate aberrations in glucose metabolism underlying an individual's disease. Using multivariable logistic regression, we combine clinical data with data assimilation to predict post-operative glycemic outcomes at 12 months. Models using data assimilation sans insulin had comparable performance to models using oral glucose tolerance test glucose and insulin. Our best performing models used data assimilation and had an area under the receiver operating characteristic curve of 0.77 (95% confidence interval 0.7665, 0.7734) and mean average precision of 0.6258 (0.6206, 0.6311). We show that data assimilation extracts knowledge from mechanistic models of glucose metabolism to infer future glycemic states from limited clinical data. This method can provide a pathway to predict long-term, post-surgical glycemic states by estimating the contributions of insulin resistance and limitations of insulin secretion to pre-operative glucose metabolism.

Weight loss between glucagon-like peptide-1 receptor agonists and bariatric surgery in adults with obesity: A systematic review and meta-analysis

OBJECTIVE

Glucagon-like peptide-1 (GLP-1) receptor agonists recently demonstrated 15% to 20% weight loss in adults with obesity, a range which has previously been achieved only with bariatric surgery. This systematic review and meta-analysis compares weight loss between GLP-1 receptor agonists and bariatric surgery.

METHODS

The databases MEDLINE, MEDLINE In-Process, MEDLINE Epubs Ahead of Print, Embase Classic + Embase (OvidSP), and Cochrane (Wiley) were searched from inception to April 21, 2021, for randomized controlled trials and observational studies. Two independent reviewers extracted data, reported risk of bias, and graded certainty of evidence. Random-effects models were used to pool change in weight, BMI, and glycated hemoglobin.

RESULTS

Six studies, encompassing 332 patients, were included. Among randomized controlled trials, mean difference in weight between all bariatric surgery types and GLP-1 receptor agonists was -22.68 kg (95% CI: -31.41 to -13.96), mean difference in BMI was -8.18 kg/m² (95% CI: -11.59 to -4.77), and mean difference in glycated hemoglobin was -1.28% (95% CI: -1.94% to -0.61%). Among observational studies, mean difference in weight was -25.11 kg (95% CI: -40.61 to -9.60), and mean difference in BMI was -10.60 kg/m² (95% CI: -17.22 to -3.98). Only one observational study reported glycemic outcomes.

CONCLUSION

In adults with obesity, bariatric surgery still confers the highest reductions in weight and BMI but confers similar effects in glycemic control when compared with GLP-1 receptor agonists.

Common, Less Common, and Unexpected Complications after Bariatric Surgery: A Pictorial Essay

Bariatric surgery has demonstrated a higher rate of success than other nonsurgical treatments in selected patients with obesity; however, like all medical procedures, postoperative complications may occur, ranging between 2 and 10% and, although rare, they can be life threatening. Complications may be unspecific (any surgery-related complications) or specific (linked to the specific surgical procedure) and can be distinguished as common, less common, and unexpected. According to the onset, they may be acute, when occurring in the first 30 days after surgery, or chronic, with a presentation after 30 days from the procedure. The aim of this pictorial essay is to review the radiological aspects of surgical techniques usually performed and the possible complications, in order to make radiologists more confident with the postsurgical anatomy and with the normal and abnormal imaging findings.

Delayed Gastric Emptying After Sleeve Gastrectomy Is Associated with Poor Weight Loss

Background

Intermediate to long-term weight regain is a major challenge following sleeve gastrectomy (SG). Physiological changes that mediate the extent of weight loss remain unclear. We aimed to determine if there were specific esophago-gastric transit and emptying alterations associated with weight regain.

Material and Methods

Participants greater than 12 months post-SG were categorized into optimal (n = 29) and poor weight loss (PWL) (n = 72). All patients underwent a liquid contrast barium swallow demonstrating normal post-surgical anatomy and a protocolized nuclear scintigraphy designed specifically to characterize gastric emptying following SG.

Results

The %total weight loss in the optimal group was 26.2 ± 10.5 vs. 14.3 ± 8.8% in the PWL group (p = 0.001). Scintigraphy showed PWL had relatively increased gastric emptying half-time (GE ^1/2t) 35 (IQR 23) min vs 19 (IQR 5.5) min (p = 0.001). The multivariate regressions delineated GE ^1/2t as the best diagnostic measure for PWL (OR 1.16; CI 1.04–1.29, p-value 0.021). The probability of PWL increased by 16% for every 1-min increase above 21 min of GE ^1/2t. A threshold of 21 min was found to have 88% sensitivity and 69% specificity predicting poor weight loss.

Conclusion

Gastric emptying half-times greater than 21 min appear to reliably correlate with poor weight loss following SG. Additionally, further elevations above 21 min in emptying half-time increase the risk of poor weight loss. We have shown nuclear scintigraphy represents a simple and accurate diagnostic tool in patients who experience poor weight loss after SG, provided substantially altered reporting references in interpreting nuclear scintigraphy are applied.

Graphical abstract

Multi-omic phenotyping reveals host-microbe responses to bariatric surgery, glycaemic control and obesity

Background

Resolution of type 2 diabetes (T2D) is common following bariatric surgery, particularly Roux-en-Y gastric bypass. However, the underlying mechanisms have not been fully elucidated.

Methods

To address this we compare the integrated serum, urine and faecal metabolic profiles of participants with obesity ± T2D (n = 80, T2D = 42) with participants who underwent Roux-en-Y gastric bypass or sleeve gastrectomy (pre and 3-months post-surgery; n = 27), taking diet into account. We co-model these data with shotgun metagenomic profiles of the gut microbiota to provide a comprehensive atlas of host-gut microbe responses to bariatric surgery, weight-loss and glycaemic control at the systems level.

Results

Here we show that bariatric surgery reverses several disrupted pathways characteristic of T2D. The differential metabolite set representative of bariatric surgery overlaps with both diabetes (19.3% commonality) and body mass index (18.6% commonality). However, the percentage overlap between diabetes and body mass index is minimal (4.0% commonality), consistent with weight-independent mechanisms of T2D resolution. The gut microbiota is more strongly correlated to body mass index than T2D, although we identify some pathways such as amino acid metabolism that correlate with changes to the gut microbiota and which influence glycaemic control.

Conclusion

We identify multi-omic signatures associated with responses to surgery, body mass index, and glycaemic control. Improved understanding of gut microbiota - host co-metabolism may lead to novel therapies for weight-loss or diabetes. However, further experiments are required to provide mechanistic insight into the role of the gut microbiota in host metabolism and establish proof of causality.

Weight-loss surgery is a highly effective treatment of type 2 diabetes in people with obesity. Interestingly, the improvement in diabetes after weight-loss surgery occurs before any significant weight-loss. Through better understanding of this metabolic improvement, weight-loss surgery provides a unique avenue to identify novel ways of treating diabetes and obesity. 

Here we combine measurements of metabolism, gut bacteria and diet in people with obesity, with or without type 2 diabetes and in patients before and after weight-loss surgery. We have used these data to identify changes associated with weight-loss surgery, obesity and diabetes. 

Improved understanding of the mechanisms behind these changes, including how changes to gut bacteria influence metabolism, may lead to new treatments for weight-loss or diabetes.

Penney et al. conduct microbial and metabolic profiling in people with obesity, with or without type 2 diabetes, undergoing two types of bariatric surgery. Integrative analysis identifies multi-omic signatures associated with response to surgery, body mass index, and glycaemic control.

A review on the beneficial effects of bariatric surgery in the management of obesity

INTRODUCTION

Obesity is a chronic disease with a complex interplay of multiple factors such as genetic, metabolic, behavioral, and environmental factors. The management of obesity includes; lifestyle modification, psychological therapy, pharmacological therapy, and bariatric surgery. To date, bariatric surgery is the most effective treatment for obesity by offering a long-term reduction in weight, remission of obesity-related complications, and improving quality of life. However, bariatric surgery is not equally effective in all patients. Thus, if we can predict who would benefit most, it will improve the risk versus benefit ratio of having surgery.

AREAS COVERED

In this narrative review, we explore the question on who will benefit the most from bariatric surgery by examining the recent evidence in the literature. In addition, we investigate the predisposing predictors of bariatric surgery response. Finally, we offer the best strategies in the clinic to explain the potential benefits of bariatric surgery to patients.

EXPERT OPINION

Bariatric surgery is an effective obesity management approach. Despite its efficacy, considerable variation of individual response exists. Thus, it is important to recognize patients that will benefit most, but at present very few predictors are available which can be clinically useful.

Sleeve Gastrectomy Reduces Glycemia but Does Not Affect Cognitive Impairment in Lean 5xFAD Mice

Obesity and hyperglycemia are risk factors for cognitive decline and for the development of Alzheimer’s Disease (AD). Bariatric surgery is an effective treatment for obesity that was shown to improve cognitive decline in obese patients. Bariatric surgery was shown to exert weight loss independent effects on metabolic diseases such as type 2 diabetes. We tested whether sleeve gastrectomy (SG), a common bariatric surgery, can affect the cognitive impairment in lean, normoglycemic female 5xFAD mice, a genetic model for AD. 5xFAD mice and wild-type (WT) littermates underwent SG or sham surgery at the age of 5 months and were tested for metabolic, behavioral, and molecular phenotypes 90 days later. SG led to a reduction in blood glucose levels and total plasma cholesterol levels in 5xFAD mice without inducing weight loss. However, the surgery did not affect the outcomes of long-term spatial memory tests in these mice. Analysis of β-Amyloid plaques corroborated the behavioral studies in showing no effect of surgery on the molecular phenotype of 5xFAD mice. In conclusion, SG leads to an improved metabolic profile in lean female 5xFAD mice without inducing weight loss but does not affect the brain pathology or behavioral phenotype. Our results suggest that the positive effects of bariatric surgery on cognitive decline in obese patients are likely attributed to weight loss and improvement in obesity sequelae, and not to weight loss independent effects of surgery.

Long-Term Trajectories in Weight and Health Outcomes Following Multidisciplinary Publicly Funded Bariatric Surgery in Patients with Clinically Severe Obesity (≥ 3 Associated Comorbidities): A Nine-Year Prospective Cohort Study in Australia

Background: Real-world data on long-term (> 5 years) weight loss and obesity-related complications after newer bariatric surgical procedures are currently limited. The aim of this longitudinal study was to examine the effectiveness and sustainability of bariatric surgery in a cohort with clinically severe obesity in a multidisciplinary publicly funded service in two teaching hospitals in New South Wales, Australia. Methods: Patients were adults with complex clinically severe obesity with a BMI ≥ 35 kg/m2 and at least three significant obesity-related comorbidities, who underwent bariatric surgeries between 2009 and 2017. Detailed obesity-related health outcomes were reported from annual clinical data and assessments for up to 9 years of follow-up. Data were also linked with the national joint replacement registry. Results: A total of 65 eligible patients were included (mean, 7; range, 3−12 significant obesity-related comorbidities); 53.8% female; age 54.2 ± 11.2 years, with baseline BMI 52.2 ± 12.5 kg/m2 and weight 149.2 ± 45.5 kg. Most underwent laparoscopic sleeve gastrectomy (80.0%), followed by laparoscopic adjustable gastric banding (10.8%) and one anastomosis gastric bypass (9.2%). Substantial weight loss was maintained over 9 years of follow-up (p < 0.001 versus baseline). Significant total weight loss (%TWL ± SE) was observed (13.2 ± 2.3%) following an initial 1-year preoperative intensive lifestyle intervention, and ranged from 26.5 ± 2.3% to 33.0 ± 2.0% between 1 and 8 years following surgery. Type 2 diabetes mellitus (T2DM), osteoarthritis-related joint pain and depression/severe anxiety were the most common metabolic, mechanical and mental health comorbidities, with a baseline prevalence of 81.5%, 75.4% and 55.4%, respectively. Clinically significant composite cumulative rates of remission and improvement occurred in T2DM (50.0−82.0%) and hypertension (73.7−82.9%) across 6 years. Dependence on continuous positive airway pressure treatment in patients with sleep-disordered breathing fell significantly from 63.1% to 41.2% in 6 years. Conclusion: Bariatric surgery using an intensive multidisciplinary approach led to significant long-term weight loss and improvement in obesity-related comorbidities among the population with clinically complex obesity. These findings have important implications in clinical care for the management of the highest severity of obesity and its medical consequences. Major challenges associated with successful outcomes of bariatric surgery in highly complex patients include improving mental health in the long run and reducing postoperative opioid use. Long-term follow-up with a higher volume of patients is needed in publicly funded bariatric surgery services to better monitor patient outcomes, enhance clinical data comparison between services, and improve multidisciplinary care delivery.

Food Intake Following Gastric Bypass Surgery: Patients Eat Less but Do Not Eat Differently

BACKGROUND

Lack of robust research methodology for assessing ingestive behavior has impeded clarification of the mediators of food intake following gastric bypass (GBP) surgery.

OBJECTIVES

To evaluate changes in directly measured 24-h energy intake (EI), energy density (ED) (primary outcomes), eating patterns, and food preferences (secondary outcomes) in patients and time-matched weight-stable comparator participants.

METHODS

Patients [n = 31, 77% female, BMI (in kg/m²) 45.5 ± 1.3] and comparators (n = 32, 47% female, BMI 27.2 ± 0.8) were assessed for 36 h under fully residential conditions at baseline (1 mo presurgery) and at 3 and 12 mo postsurgery. Participants had ad libitum access to a personalized menu (n = 54 foods) based on a 6-macronutrient mix paradigm. Food preferences were assessed by the Leeds Food Preference Questionnaire. Body composition was measured by whole-body DXA.

RESULTS

In the comparator group, there was an increase in relative fat intake at 3 mo postsurgery; otherwise, no changes were observed in food intake or body composition. At 12 mo postsurgery, patients lost 27.7 ± 1.6% of initial body weight (P < 0.001). The decline in EI at 3 mo postsurgery (-44% from baseline, P < 0.001) was followed by a partial rebound at 12 mo (-18% from baseline), but at both times, dietary ED and relative macronutrient intake remained constant. The decline in EI was due to eating the same foods as consumed presurgery and by decreasing the size (g, MJ), but not the number, of eating occasions. In patients, reduction in explicit liking at 3 mo (-11.56 ± 4.67, P = 0.007) and implicit wanting at 3 (-15.75 ± 7.76, P = 0.01) and 12 mo (-15.18 ± 6.52, P = 0.022) for sweet foods were not matched by reduced intake of these foods. Patients with the greatest reduction in ED postsurgery reduced both EI and preference for sweet foods.

CONCLUSIONS

After GBP, patients continue to eat the same foods but in smaller amounts. These findings challenge prevailing views about the dynamics of food intake following GBP surgery. This trial was registered as clinicaltrials.gov as NCT03113305.

Effects of Heterozygous Variants in the Leptin-Melanocortin Pathway on Roux-en-Y Gastric Bypass Outcomes: a 15-Year Case-Control Study

INTRODUCTION

Heterozygous variants in the leptin-melanocortin pathway are associated with obesity. However, their effect on the long-term outcomes after Roux-en-Y gastric bypass (RYGB) is still unknown.

METHODS

In this matched case-control study, 701 participants from the Mayo Clinic Biobank with a history of RYGB were genotyped. Sixty-three patients had a heterozygous variant in the leptin-melanocortin pathway. After excluding patients with potential confounders, carriers were randomly matched (on sex, age, body mass index [BMI], and years since surgery) with two non-carrier controls. The electronic medical record of carriers and matched non-carriers was reviewed for up to 15 years after RYGB.

RESULTS

A total of 50 carriers and 100 matched non-carriers with a history of RYGB were included in the study. Seven different genes (LEPR, PCSK1, POMC, SH2B1, SRC1, MC4R, and SIM1) in the leptin-melanocortin pathway were identified. At the time of surgery, the mean age was 50.8 ± 10.6 years, BMI 45.6 ± 7.3 kg/m², and 79% women. There were no differences in postoperative years of follow-up, Roux limb length, or gastric pouch size between groups. Fifteen years after RYGB, the percentage of total body weight loss (%TBWL) in carriers was - 16.6 ± 10.7 compared with - 28.7 ± 12.9 in non-carriers (diff = 12.1%; 95% CI, 4.8 to 19.3) and the percentage of weight regain after maximum weight loss was 52.7 ± 29.7 in carriers compared with 29.8 ± 20.7 in non-carriers (diff = 22.9%; 95% CI, 5.3 to 40.5). The nadir %TBWL was lower - 32.1 ± 8.1 in carriers compared with - 36.8 ± 10.4 in non-carriers (diff = 4.8%; 95% CI 1.8 to 7.8).

CONCLUSIONS

Carriers of a heterozygous variant in the leptin-melanocortin pathway have a progressive and significant weight regain in the mid- and long-term after RYGB. Genotyping patients experiencing significant weight regain after RYGB could help implement multidisciplinary and individualized weight loss interventions to improve weight maintenance after surgery.

Molecular Basis of Bile Acid-FXR-FGF15/19 Signaling Axis

Bile acids (BAs) are a group of amphiphilic molecules consisting of a rigid steroid core attached to a hydroxyl group with a varying number, position, and orientation, and a hydrophilic side chain. While BAs act as detergents to solubilize lipophilic nutrients in the small intestine during digestion and absorption, they also act as hormones. Farnesoid X receptor (FXR) is a nuclear receptor that forms a heterodimer with retinoid X receptor α (RXRα), is activated by BAs in the enterohepatic circulation reabsorbed via transporters in the ileum and the colon, and plays a critical role in regulating gene expression involved in cholesterol, BA, and lipid metabolism in the liver. The FXR/RXRα heterodimer also exists in the distal ileum and regulates production of fibroblast growth factor (FGF) 15/FGF19, a hormone traveling via the enterohepatic circulation that activates hepatic FGF receptor 4 (FGFR4)-β-klotho receptor complex and regulates gene expression involved in cholesterol, BA, and lipid metabolism, as well as those regulating cell proliferation. Agonists for FXR and analogs for FGF15/19 are currently recognized as a promising therapeutic target for metabolic syndrome and cholestatic diseases.

Generation and characterization of a mouse model for one anastomosis gastric bypass surgery

One anastomosis gastric bypass (OAGB) surgery became a common bariatric procedure in recent years. In this surgery, the distal stomach, duodenum, and proximal jejunum are bypassed, leading to weight loss, improvement in metabolic parameters, and a change in hormonal secretion. We sought to generate and characterize a mouse model for OAGB. Mice fed for 26 wk on a high-fat diet were assigned to OAGB, sham surgery, or caloric restriction and were followed for 50 more days on a high-fat diet. Physiological and histological parameters of the mice were compared during and at the end of the experiment. OAGB-operated mice lost weight and displayed low levels of plasma lipids, high insulin sensitivity, and rapid glucose metabolism compared with sham-operated mice. OAGB-operated mice had higher energy expenditure, higher levels of glucagon-like peptide (GLP-1), and lower albumin than weight-matched calorie-restricted mice. There was no difference in the histology of the endocrine pancreas. The livers of OAGB mice had little hepatic steatosis yet presented with a large number of phagocytic cells. The OAGB mouse model recapitulates many of the phenotypes described in patients that underwent OAGB and enables molecular and physiological studies on the outcome of this surgery.NEW & NOTEWORTHY A mouse model for one anastomosis gastric bypass (OAGB) surgery displays similar outcomes to clinical reports and enables to study the weight loss-dependent and -independent effects of this bariatric surgery.

Nutritional Management in Bariatric Surgery Patients

The obesity epidemic, mainly due to lifestyle changes in recent decades, leads to serious comorbidities that reduce life expectancy. This situation is affecting the health policies of many nations around the world. Traditional measures such as diet, physical activity, and drugs are often not enough to achieve weight loss goals and to maintain the results over time. Bariatric surgery (BS) includes various techniques, which favor rapid and sustained weight loss. BS is a useful and, in most cases, the best treatment in severe and complicated obesity. In addition, it has a greater benefit/risk ratio than non-surgical traditional therapies. BS can allow the obese patient to lose weight quickly compared with traditional lifestyle changes, and with a greater probability of maintaining the results. Moreover, BS promotes improvements in metabolic parameters, even diabetes remission, and in the quality of life. These changes can lead to an increase of life expectancy by over 6 years on average. The nutrition of people before and after BS must be the subject of indications from a trained staff, and patients must be followed in the subsequent years to reduce the risk of malnutrition and the associated problems. In particular, it is still debated whether it is necessary to lose weight prior to surgery, a procedure that can facilitate the surgeon's work reducing the surgical risk, but at the same time, lengthens preparation times increasing the risks associated with concomitant pathologies. Furthermore, preventing nutritional deficiencies prior to the intervention can improve the results and reduce short- and long-term mortality.