Long-Term Modulation of Appetitive Hormones and Sweet Cravings After Adjustable Gastric Banding and Roux-en-Y Gastric Bypass

The Interplay Between Psychological and Neurobiological Predictors of Weight Regain: A Narrative Review

Introduction: Obesity is a global health problem requiring effective interventions to achieve weight loss and maintain it in the long term. A major challenge for clinicians is weight regain (WR), defined as progressive weight gain following successful weight loss. WR is affected by multiple factors, including psychological traits linked to specific brain alterations. Understanding these mechanisms is crucial in developing strategies to prevent WR and to ensure effective weight control. Objectives: This narrative review aims to gather current findings on the psychological and neurobiological determinants of WR and to discuss the interplay between these factors. Methods: A literature search was conducted on PubMed, Medline, and Web of Science for English-language studies published between December 1990 and November 2024. Results: WR is driven by interconnected psychological and neurobiological factors that influence eating behavior and the regulation of body weight. Certain personality traits and emotional patterns are associated with specific changes in brain activity, which together affect vulnerability to WR. Although distinct mechanisms can be identified, the complexity of homeostatic and nonhomeostatic appetite control suggests that no single factor predominates. Conclusions: This review highlights the dynamic interplay between psychological and neurobiological predictors of WR. However, due to the narrative nature of this review, the focus on selected determinants, and the limited quality and size of the available studies, further research is needed to comprehensively understand causality and to improve relapse prevention strategies.

Nomogram for Predicting Suboptimal Weight Loss at Three Years after Roux-en-Y Gastric Bypass Surgery in Chinese Patients with Obesity and Type 2 Diabetes

INTRODUCTION

Strategies to address suboptimal weight loss after Roux-en-Y gastric bypass (RYGB) can be developed if at-risk patients are identified in advance. This study aimed to build a pre-surgery prediction nomogram for early prediction of insufficient weight loss (IWL) or weight regain (WR) after bariatric surgery in Chinese patients.

METHODS

In this retrospective study, 187 patients with obesity and type 2 diabetes who underwent laparoscopic RYGB were followed yearly for 3 years. Suboptimal weight loss included IWL and WR. IWL was defined as a total weight loss percentage of <25% at 1 year postoperatively, and WR was defined as a maximum weight loss percentage of >20% at 3 years postoperatively. Multivariate logistic regression was performed to identify independent predictors and to establish a nomogram to predict the occurrence of suboptimal weight loss.

RESULTS

Multivariate logistic regression revealed that male sex (OR 4.268, 95% CI: 1.413-12.890), body mass index (OR 0.816, 95% CI: 0.705-0.946), and glycated hemoglobin (OR 1.493, 95% CI: 1.049-2.126) were independent predictors of IWL/WR. The AUC value of the nomogram constructed from the above three factors was 0.781. The Hosmer-Lemeshow test showed that the model had a good fit (p = 0.143). The calibration curve of the nomogram is close to an ideal diagonal line. Furthermore, the decision curve analysis demonstrated the good net benefits of the model.

CONCLUSIONS

A nomogram based on pre-surgery factors was developed to predict postoperative IWL/WR. This provides a convenient and useful tool for predicting suboptimal weight loss before surgery.

Possible Interaction Between Physical Exercise and Leptin and Ghrelin Changes Following Roux-en-Y Gastric Bypass in Sarcopenic Obesity Patients-A Pilot Study

INTRODUCTION

Leptin and ghrelin are two hormones that play a role in weight homeostasis. Leptin, which is produced primarily by adipocytes and is dependent on body fat mass, suppresses appetite and increases energy expenditure. Conversely, ghrelin is the "hunger hormone", it stimulates appetite and promotes fat storage. Bariatric surgery significantly alters the levels and activity of these hormones, contributing to weight loss and metabolic improvements. Clarifying the interplay between bariatric surgery, weight loss, physical exercise, leptin, and ghrelin is essential in developing comprehensive strategies for optimizing the long-term outcomes for candidates who have undergone bariatric surgery, especially for sarcopenic patients.

METHODS

This was a randomized controlled study with two groups (n = 22). The patients in both groups had obesity and sarcopenia. A Roux-en-Y-gastric bypass (RYGB) procedure was performed on all patients. The intervention group participated in a structured exercise program three times per week, beginning one month after surgery and lasting 16 weeks. Patient assessment was performed before surgery (baseline) and after the completion of the exercise program. The control group received the usual standard of care and was assessed similarly.

RESULTS

After surgery, weight, BMI, and lean mass decreased significantly in both groups between the baseline and the second assessment. Leptin levels were not significantly different between baseline and the second assessment in the physical exercise group, but were significantly lower in the control group (p = 0.05). Ghrelin levels increased over time in both groups, but the differences were not significant. When we associated leptin (the dependent variable) with weight (the independent variable), we found that lower weight was associated with lower leptin levels. A similar relationship was also observed between the leptin and sarcopenia parameters (muscle strength and mass), as well as in the bone health parameters (bone mineral density and t-score). Higher ghrelin levels were significantly associated with higher t-scores and z-scores (p < 0.05).

CONCLUSION

Exercise has been shown to have a significant effect on leptin and ghrelin levels after bariatric surgery. By incorporating regular physical activity into their lifestyle, bariatric patients can optimize their weight loss outcomes and improve their overall health. After the physical exercise protocol, patients in the intervention group revealed more established leptin levels, which may indicate a protected pattern concerning decreased leptin levels. An unfavorable profile was evidenced, according to which greater weight loss, sarcopenia, and osteoporosis were associated with lower leptin levels.

Impact of Recurrent Weight Gain Thresholds on Comorbid Conditions Progression Following Laparoscopic Sleeve Gastrectomy

INTRODUCTION

Defining recurrent weight gain after metabolic bariatric surgery poses a significant challenge. Our study aimed to standardize recurrent weight gain measurements in patients undergoing laparoscopic sleeve gastrectomy (LSG) and ascertain its association with comorbidity progression.

METHODS

We conducted a retrospective data analysis on 122 patients who underwent LSG, tracking their progress over 2-7 years. Data on weight, blood pressure measurements, and laboratory tests were collected, focusing on the postoperative period to identify nadir weight, total weight loss, and recurrent weight gain.

RESULTS

Significant weight loss and comorbidity remission were noted, with diabetes, hypertension, and dyslipidemia showing substantial remission rates of 85.71%, 68.24%, and 85.37%, respectively. The median recurrent weight gain was 6.30 kg within 12 months of the nadir. Progression proportion of diabetes, hypertension, and dyslipidemia were 8.20%, 44.26%, and 40.98%, respectively. Hypertension progression was strongly associated with a recurrent weight gain ≥ 10 kg and ≥ 20% of maximum weight loss. Dyslipidemia progression was significantly correlated with recurrent weight gain ≥ 10 kg and ≥ 20% of maximum weight loss. Diabetes progression was significantly correlated with recurrent weight gain ≥ 10% of pre-surgery body weight and ≥ 25% of maximum weight loss. A ≥ 10% weight gain of maximum weight loss did not significantly impact the progression of these conditions.

CONCLUSION

Recurrent weight gain ≥ 20% of maximum weight loss can be treated as a specific threshold indicating comorbidity progression post-LSG. Standardizing the measurement of recurrent weight gain can help healthcare providers to implement targeted management strategies to optimize long-term health outcomes.

Weight Regain after Metabolic Surgery: Beyond the Surgical Failure

Patients undergoing metabolic surgery have factors ranging from anatomo-surgical, endocrine metabolic, eating patterns and physical activity, mental health and psychological factors. Some of the latter can explain the possible pathophysiological neuroendocrine, metabolic, and adaptive mechanisms that cause the high prevalence of weight regain in postbariatric patients. Even metabolic surgery has proven to be effective in reducing excess weight in patients with obesity; some of them regain weight after this intervention. In this vein, several studies have been conducted to search factors and mechanisms involved in weight regain, to stablish strategies to manage this complication by combining metabolic surgery with either lifestyle changes, behavioral therapies, pharmacotherapy, endoscopic interventions, or finally, surgical revision. The aim of this revision is to describe certain aspects and mechanisms behind weight regain after metabolic surgery, along with preventive and therapeutic strategies for this complication.

Suboptimal Weight Loss 13 Years After Roux-en-Y Gastric Bypass Is Associated with Blunted Appetite Response

PURPOSE

Bariatric surgery remains the most efficient treatment to achieve a sustained weight loss. However, a large proportion of patients experience suboptimal weight loss (SWL). The exact mechanisms involved remain to be fully elucidated, but the homeostatic appetite control system seems to be involved. The aim of this study was, therefore, to compare the plasma concentration of gastrointestinal hormones, and appetite ratings, between those experiencing SWL and optimal weight loss (OWL) after Roux-en-Y gastric bypass (RYGB).

MATERIALS AND METHODS

Fifty participants from the Bariatric Surgery Observation Study (BAROBS) experiencing either SWL or OWL (< or ≥ 50% of excess weight loss (EWL), respectively) > 13 years post-RYGB were compared to 25 non-surgical controls. Plasma concentrations of acylated ghrelin (AG), total glucagon-like peptide-1 (GLP-1), total peptide YY (PYY), cholecystokinin (CCK), and subjective ratings of hunger, fullness, desire to eat (DTE), and prospective food consumption (PFC) were assessed in the fasting and postprandial (area under the curve (AUC)) states.

RESULTS

Those experiencing OWL presented with higher basal AG and GLP-1 iAUC, and lower AG iAUC compared with SWL and controls. Additionally, both bariatric groups presented with higher PYY and CCK iAUC compared to controls. PFC tAUC was also lower in OWL compared to the SWL group. Total weight loss was positively correlated with GLP-1 tAUC and negatively correlated with fasting and tAUC DTE and PFC tAUC.

CONCLUSIONS

SWL > 13 years post-RYGB is associated with lower basal ghrelin, as well as a weaker satiety response to a meal. Future studies should investigate the causality of these associations.

Bariatric Surgery and Gut-Brain-Axis Driven Alterations in Cognition and Inflammation

Obesity is associated with systemic inflammation, comorbidities like diabetes, cardiovascular disease and several cancers, cognitive decline and structural and functional brain changes. To treat, or potentially prevent these related comorbidities, individuals with obesity must achieve long-term sustainable weight loss. Often life style interventions, such as dieting and increased physical activity are not successful in achieving long-term weight loss. Meanwhile bariatric surgery has emerged as a safe and effective procedure to treat obesity. Bariatric surgery causes changes in physiological processes, but it is still not fully understood which exact mechanisms are involved. The successful weight loss after bariatric surgery might depend on changes in various energy regulating hormones, such as ghrelin, glucagon-like peptide-1 and peptide YY. Moreover, changes in microbiota composition and white adipose tissue functionality might play a role. Here, we review the effect of obesity on neuroendocrine effects, microbiota composition and adipose tissue and how these may affect inflammation, brain structure and cognition. Finally, we will discuss how these obesity-related changes may improve after bariatric surgery.

Laparoscopic adjustable gastric banding with liraglutide in adults with obesity and type 2 diabetes (GLIDE): a pilot randomised placebo controlled trial

INTRODUCTION

Obesity drives type 2 diabetes (T2DM) development. Laparoscopic adjustable gastric banding (LAGB) has lower weight reduction than other bariatric procedures. Liraglutide, a GLP-1 receptor agonist, improves weight and glycaemic control in patients with T2DM. This study aimed to determine the efficacy and safety of liraglutide 1.8 mg in participants undergoing LAGB.

METHODS

GLIDE, a pilot randomised, double-blind, placebo-controlled trial, evaluated LAGB with either liraglutide 1.8 mg or placebo in participants with T2DM and obesity. Participants were randomised (1:1) to 6-months therapy post-LAGB, with further 6 months off-treatment follow-up. The primary outcome was change in HbA1c from randomisation to the end of treatment, secondary outcomes included body weight change. A sample size of 58 (29 per group) had 80% power to detect a 0.6% difference in HbA1c between groups.

RESULTS

Twenty-seven participants were randomised to liraglutide (n = 13) or placebo (n = 14). Multivariate analysis showed no difference between placebo and liraglutide arms in HbA1c at 6 months (HbA1c:0.2 mmol/mol, -11.3, 11.6, p = 0.98) however, at 12 months HbA1c was significantly higher in the liraglutide arm (HbA1c:10.9 mmol/mol, 1.1, 20.6, p = 0.032). There was no difference between arms in weight at 6 months (BW:2.0 kg, -4.2, 8.1, p = 0.50), however, at 12 months weight was significantly higher in the liraglutide arm (BW:8.2 kg, 1.6, 14.9, p = 0.02). There were no significant differences in adverse events between groups.

CONCLUSIONS

Our pilot data suggest no additional improvement in glycaemic control or BW with LAGB and liraglutide therapy. However, this trial was significantly underpowered to detect a significant change in the primary or secondary outcomes. Further trials are needed to investigate whether GLP-1 agonists, and particularly with more effective weekly agents (i.e. semaglutide or tirzepatide), are of benefit following metabolic surgery.

CLINICAL TRIAL REGISTRATION

EudraCT number 2015-005402-11.

Significance of Hormone Alteration Following Bariatric Surgery

The prevalence of obesity has increased significantly over the last several decades, and with its increase comes a wide variety of comorbidities, such as diabetes and cardiovascular disease. Traditionally, diet and exercise have been prescribed for individuals to try and regain control of their weight and health status. Despite this successful method, the compliance rate is significantly below the desired amount. Over the last few decades, a new treatment has been offered to significantly decrease an individual's weight to an optimal BMI between 18 and 25 kg/m2. Bariatric surgery has been proposed to be the most appropriate treatment for obesity, and there are several different types of bariatric surgery: Roux-en-Y gastric bypass (RYGB), biliopancreatic diversion with duodenal switch (BPD-DS), adjustable gastric band (AGB), and sleeve gastrectomy (SG). Hormones may be significantly involved in losing and maintaining weight loss. This paper aims to evaluate hormone changes in appetite suppression, appetite activation, glycemic control, and lipid metabolism and how these impact overall weight loss concerning the most prominent surgeries. The hormones assessed were ghrelin, insulin, leptin, GLP-1, PYY, and adiponectin, and their levels before and after each surgery were compared. RYGB is one of the most successful types of bariatric surgeries, and this correlates with it having the most suppressed levels of ghrelin, insulin, and leptin following surgery with a slow return to normal. RYGB has also led to the most significant increased levels of PYY, pre- and post-prandial GLP-1, and adiponectin. Hormones following SG followed the hormone trend after RYGB but were not as prominent. BDP-DS has the highest success rate. However, numerous adverse effects have limited the amount of studies assessing the surgery. What was present was not as significant as RYGB, possibly due to manipulation.

Weight loss trend after bariatric surgery in a population of obese patients

BACKGROUND AND AIMS

Bariatric Surgery (BS) is a therapeutic option in patients with severe obesity whose non-surgical techniques have failed. No work has previously explored trajectories of weight loss and how long this was maintained. Aim of study is to describe effect of BS and nutritional intervention on body weight trend in patients with obesity.

METHODS

792 patients who underwent BS from 1996 to 2021 were included. The Protocol provides Laparoscopic Sleeve Gastrectomy (LSG), Vertical Gastroplasty (VBG) and Roux-en-Y Gastric Bypass (GB). %Total Weight Loss (%TWL) and %Excess Weight Loss (%EWL) were evaluated in three cohort of patients. Cumulative incidence of clinical goal after surgery was calculated at two and five years after BS.

RESULTS

At two years of follow-up, average %TWL and %EWL were 31.2% (95% CI = 29.0-33.4%) and 71% (95% CI = 65.4-76.5%) for VBG, 34.7% (95% CI = 33.8-35.6%) and 78.0% (95% CI = 75.9-89.1%) for GB and 33.8% (95% CI = 32.5-35.1%) and 68.8% (95% CI = 66.1-71.6%) for LSG. At two years from surgery the cumulative incidence of clinical goal was 70.7% (95% CI = 59.1-79.1%) for VBG, 86.4% (95% CI = 82.4-89.6%) for GB and 83.4% (95% CI = 76.0-87.1%) for LSG. At five years from surgery, average % TWL and % EWL were 22.5% (95% CI = 10.2-34.8%) and 58.2% (95% CI = 28.4-88.1%) for VBG, 31.8% (95% CI = 30.2-33.3%) and 70.8% (95% CI = 67.5-74.1%) for GB and 29.5% (95% CI = 26.2-32.8%) and 62.0% (95% CI = 53.4-70.6%) for LSG respectively. At five years after having reached clinical goal the share of people who were able to maintain their weight was 49.5% (95% CI = 30.8-79.6%) for VBG, 69.5% (95% CI = 58.3-82.8%) for GB and 55.9% (95% CI = 42.1-74.3%) for LSG. The median time of clinical goal maintaining was 4.8 years for VBG (95% CI lower limit = 4.1), 6.6 years for GB (95% CI lower limit = 6.2) and 5.3 years for LSG (95% CI lower limit = 4.8).

CONCLUSIONS

Our work confirm effectiveness of BS in patients with obesity and show that who do not reach clinical goal within 2 years, hardly will reach it later and suggest necessity for a medium and long-term follow-up to prevent weight regain.

Weight Regain and Ingestive Behavior in Women after Metabolic Surgery

This study investigated associations between maladaptive ingestive behaviors and weight regain in women who underwent metabolic surgery 2-10 years ago. Using a web-based survey, we assessed emotional, external, and restrained eating (Dutch Eating Behavior Questionnaire-DEBQ), food cravings (Food-Craving Inventory-FCI), and other behaviors (e.g., Eating Disorder Examination Questionnaire-EDE-Q; Alcohol Use Disorder Identification Test-Concise-AUDIT-C) in 36 women (42.9 ± 9.5 years old) post-surgery. We found that weight regain was specifically associated with increased frequency of cravings for sweets (r = 0.43), higher global scores in the EDE-Q (r = 0.38), and time elapsed since surgery (r = 0.35; all p's < 0.04). Multiple regression analysis revealed that the association between weight regain and sweet cravings interacted with time after surgery (p = 0.04), with the strongest association observed in women assessed closer to the surgery (i.e., 2.0-2.8 years). The combination of time after surgery and its interaction with sweet cravings accounted for 31% of the individual variations in weight regain (p = 0.005). Notably, among participants who reported alcohol consumption (31 of 36), 55% had an AUDIT-C score indicating hazardous drinking. These findings highlight the relevance of attending to patients' reports of frequent sweet cravings and screening for alcohol use to enhance strategies tailored to prevent weight regain and alcohol-related health problems post-surgery.

Tripeptide gut hormone infusion does not alter food preferences or sweet taste function in volunteers with obesity and prediabetes/diabetes but promotes restraint eating: A secondary analysis of a randomized single-blind placebo-controlled study

AIMS

To investigate whether the elevation in postprandial concentrations of the gut hormones glucagon-like peptide-1 (GLP-1), oxyntomodulin (OXM) and peptide YY (PYY) accounts for the beneficial changes in food preferences, sweet taste function and eating behaviour after Roux-en-Y gastric bypass (RYGB).

MATERIALS AND METHODS

This was a secondary analysis of a randomized single-blind study in which we infused GLP-1, OXM, PYY (GOP) or 0.9% saline subcutaneously for 4 weeks in 24 subjects with obesity and prediabetes/diabetes, to replicate their peak postprandial concentrations, as measured at 1 month in a matched RYGB cohort (ClinicalTrials.gov NCT01945840). A 4-day food diary and validated eating behaviour questionnaires were completed. Sweet taste detection was measured using the method of constant stimuli. Correct sucrose identification (corrected hit rates) was recorded, and sweet taste detection thresholds (EC50s: half maximum effective concencration values) were derived from concentration curves. The intensity and consummatory reward value of sweet taste were assessed using the generalized Labelled Magnitude Scale.

RESULTS

Mean daily energy intake was reduced by 27% with GOP but no significant changes in food preferences were observed, whereas a reduction in fat and increase in protein intake were seen post-RYGB. There was no change in corrected hit rates or detection thresholds for sucrose detection following GOP infusion. Additionally, GOP did not alter the intensity or consummatory reward value of sweet taste. A significant reduction in restraint eating, comparable to the RYGB group was observed with GOP.

CONCLUSION

The elevation in plasma GOP concentrations after RYGB is unlikely to mediate changes in food preferences and sweet taste function after surgery but may promote restraint eating.

Characteristics and outcomes for patients undergoing revisional bariatric surgery due to persistent obesity: a retrospective cohort study of 10,589 patients

BACKGROUND

Revisional bariatric surgery in an option for patients who experience weight regain or inadequate weight loss after primary elective bariatric procedures. However, there is conflicting data on safety outcomes of revisional procedures. We aim to characterize patient demographics, procedure type, and safety outcomes for those undergoing revisional compared to initial bariatric interventions to guide management of these patients.

METHODS

The 2020 Metabolic and Bariatric Accreditation and Quality Improvement Program (MBSAQIP) registry was analyzed, comparing primary elective to revisional bariatric procedures for inadequate weight loss. Bivariate analysis was performed to determine between group differences. Multivariable logistic regression determined factors associated with serious complications or mortality.

RESULTS

We evaluated 158,424 patients, including 10,589 (6.7%) revisional procedures. Patients undergoing revisional procedures were more like to be female (85.5% revisional vs. 81.0% initial; p < 0.001), had lower body mass index (43.6 ± 7.8 kg/m² revisional vs. 45.2 ± 7.8 kg/m² initial; p < 0.001), and less metabolic comorbidities than patients undergoing primary bariatric surgery. The most common revisional procedures were Roux-en-Y gastric bypass (48.4%) and sleeve gastrectomy (32.5%). Revisional procedures had longer operative duration compared to primary procedures. Patients undergoing revisional procedures were more likely to experience readmission to hospital (4.8% revisional vs. 2.9% initial; p < 0.001) and require reoperation (2.4% revisional vs. 1.0% initial; p < 0.001) within 30 days of the procedure. Revisional procedures were independently associated with increased serious complications (OR 1.49, CI 1.36-1.64, p < 0.001) but were not a significant predictor of 30-day mortality (OR 0.74, CI 0.36-1.50, p = 0.409).

CONCLUSIONS

In comparison to primary bariatric surgery, patients undergoing revisional procedures have less metabolic comorbidities. Revisional procedures have worse perioperative outcomes and are independently associated with serious complications. These data help to contextualize outcomes for patients undergoing revisional bariatric procedures and to inform decision making in these patients.

Computational approaches to predicting treatment response to obesity using neuroimaging

Obesity is a worldwide disease associated with multiple severe adverse consequences and comorbid conditions. While an increased body weight is the defining feature in obesity, etiologies, clinical phenotypes and treatment responses vary between patients. These variations can be observed within individual treatment options which comprise lifestyle interventions, pharmacological treatment, and bariatric surgery. Bariatric surgery can be regarded as the most effective treatment method. However, long-term weight regain is comparably frequent even for this treatment and its application is not without risk. A prognostic tool that would help predict the effectivity of the individual treatment methods in the long term would be essential in a personalized medicine approach. In line with this objective, an increasing number of studies have combined neuroimaging and computational modeling to predict treatment outcome in obesity. In our review, we begin by outlining the central nervous mechanisms measured with neuroimaging in these studies. The mechanisms are primarily related to reward-processing and include "incentive salience" and psychobehavioral control. We then present the diverse neuroimaging methods and computational prediction techniques applied. The studies included in this review provide consistent support for the importance of incentive salience and psychobehavioral control for treatment outcome in obesity. Nevertheless, further studies comprising larger sample sizes and rigorous validation processes are necessary to answer the question of whether or not the approach is sufficiently accurate for clinical real-world application.

Appetite Changes in Weight Regain and Weight Maintenance After Roux-en-Y Gastric Bypass

PURPOSE

Roux-en-Y gastric bypass (RYGB) surgery produces significant weight loss. However, a number of patients experience weight regain years after surgery. Factors driving weight regain after surgical interventions are currently being explored. Our objective was to investigate appetite-related measures associated with weight regain after RYGB surgery.

MATERIALS AND METHODS

Using a cross-sectional design, 29 participants (49.6 ± 9.1 years of age; current BMI 32.4 ± 4.7 kg/m², 43.6 ± 8.9 months post-RYGB) were stratified into tertiles according to weight regain per month after nadir (weight maintenance (WM), n = 9; low weight regain (LWR), n = 10; and high weight regain (HWR), n = 10). The average weight regain was, by design, significantly different between the groups (WM = 2.2 ± 2.5 kg; LWR = 10.0 ± 3.4 kg; HWR = 14.9 ± 6.3 kg regained, p < 0.05). Appetite (visual analog scales), olfactory performance ("sniffin sticks"), eating behaviors (Three Factor Eating Questionnaire), food reward (Leeds Food Preference Questionnaire), and appetite-related hormones (ghrelin, PYY, GLP-1 and leptin) were measured fasting and in response to a standardized test meal.

RESULTS

Dietary restraint was significantly higher than clinical cutoffs in WM and LWR (p < 0.05). As expected, significant time effects were noted for ghrelin, PYY, and GLP-1, but there were no group differences.

CONCLUSION

The results suggest that appetite-related outcomes are similar across individuals who have maintained weight loss and experienced regain following RYGB.

Neurohormonal Changes in the Gut-Brain Axis and Underlying Neuroendocrine Mechanisms following Bariatric Surgery

Obesity is a complex, multifactorial disease that is a major public health issue worldwide. Currently approved anti-obesity medications and lifestyle interventions lack the efficacy and durability needed to combat obesity, especially in individuals with more severe forms or coexisting metabolic disorders, such as poorly controlled type 2 diabetes. Bariatric surgery is considered an effective therapeutic modality with sustained weight loss and metabolic benefits. Numerous genetic and environmental factors have been associated with the pathogenesis of obesity, while cumulative evidence has highlighted the gut-brain axis as a complex bidirectional communication axis that plays a crucial role in energy homeostasis. This has led to increased research on the roles of neuroendocrine signaling pathways and various gastrointestinal peptides as key mediators of the beneficial effects following weight-loss surgery. The accumulate evidence suggests that the development of gut-peptide-based agents can mimic the effects of bariatric surgery and thus is a highly promising treatment strategy that could be explored in future research. This article aims to elucidate the potential underlying neuroendocrine mechanisms of the gut-brain axis and comprehensively review the observed changes of gut hormones associated with bariatric surgery. Moreover, the emerging role of post-bariatric gut microbiota modulation is briefly discussed.

Long-Term Weight Outcomes after Bariatric Surgery: A Single Center Saudi Arabian Cohort Experience

BACKGROUND

Obesity is considered a global chronic disease requiring weight management through lifestyle modification, pharmacotherapy, or weight loss surgery. The dramatic increase in patients with severe obesity in Saudi Arabia is paralleled with those undergoing bariatric surgery. Although known to be beneficial in the short term, the long-term impacts of surgery within this group and the sustainability of weight loss after surgery remains unclear.

OBJECTIVES

We aimed to assess the long-term weight outcomes after bariatric surgery.

SETTING

The study was conducted at King Khalid University Hospital (KKUH), King Saud University Medical City (KSUMC) in Riyadh, Saudi Arabia.

METHODS

An observational prospective cohort study on adult patients with severe obesity undergoing bariatric surgery (sleeve gastrectomy (SG) or Roux-en Y gastric bypass (RYGB)) during the period between 2009 and 2015 was conducted. Weight loss patterns were evaluated pre- and post-surgery through clinical and anthropometric assessments. Absolute weight loss was determined, and outcome variables: percent excess weight loss (%EWL), percent total weight loss (%TWL), and percent weight regain (%WR), were calculated. Statistical analysis using univariate and multivariate general linear modelling was carried out.

RESULTS

A total of 91 (46 males and 45 females) patients were included in the study, with the majority belonging to the SG group. Significant weight reductions were observed at 1 and 3 years of follow-up (p < 0.001) from baseline. The %EWL and %TWL were at their maximum at 3 years (72.4% and 75.8%) and were comparable between the SG and RYGB. Decrements in %EWL and %TWL and increases in %WR were seen from 3 years onwards from bariatric surgery until the study period ended. The yearly follow-up attrition rate was 20.8% at 1 year post-surgery, 26.4% at year 2, 31.8% at year 3, 47.3% at year 4, 62.6% at year 5, and 79.1% at end of study period (at year 6).

CONCLUSION

The major challenge to the successful outcome of bariatric surgery is in maintaining weight loss in the long-term and minimizing weight regain. Factors such as the type of surgery and gender need to be considered before and after surgery, with an emphasis on the need for long-term follow-up to enssure the optimal benefits from this intervention.

Sweet Taste Is Complex: Signaling Cascades and Circuits Involved in Sweet Sensation

Sweetness is the preferred taste of humans and many animals, likely because sugars are a primary source of energy. In many mammals, sweet compounds are sensed in the tongue by the gustatory organ, the taste buds. Here, a group of taste bud cells expresses a canonical sweet taste receptor, whose activation induces Ca²⁺ rise, cell depolarization and ATP release to communicate with afferent gustatory nerves. The discovery of the sweet taste receptor, 20 years ago, was a milestone in the understanding of sweet signal transduction and is described here from a historical perspective. Our review briefly summarizes the major findings of the canonical sweet taste pathway, and then focuses on molecular details, about the related downstream signaling, that are still elusive or have been neglected. In this context, we discuss evidence supporting the existence of an alternative pathway, independent of the sweet taste receptor, to sense sugars and its proposed role in glucose homeostasis. Further, given that sweet taste receptor expression has been reported in many other organs, the physiological role of these extraoral receptors is addressed. Finally, and along these lines, we expand on the multiple direct and indirect effects of sugars on the brain. In summary, the review tries to stimulate a comprehensive understanding of how sweet compounds signal to the brain upon taste bud cells activation, and how this gustatory process is integrated with gastro-intestinal sugar sensing to create a hedonic and metabolic representation of sugars, which finally drives our behavior. Understanding of this is indeed a crucial step in developing new strategies to prevent obesity and associated diseases.

Weight Regain and Insufficient Weight Loss After Bariatric Surgery: Definitions, Prevalence, Mechanisms, Predictors, Prevention and Management Strategies, and Knowledge Gaps-a Scoping Review

Some patients experience weight regain (WR) or insufficient weight loss (IWL) after bariatric surgery (BS). We undertook a scoping review of WR and IWL after BS. We searched electronic databases for studies addressing the definitions, prevalence, mechanisms, clinical significance, preoperative predictors, and preventive and treatment approaches including behavioral, pharmacological, and surgical management strategies of WR and IWL. Many definitions exist for WR, less so for IWL, resulting in inconsistencies in the reported prevalence of these two conditions. Mechanisms and preoperative predictors contributing to WR are complex and multifactorial. A range of the current knowledge gaps are identified and questions that need to be addressed are outlined. Therefore, there is an urgent need to address these knowledge gaps for a better evidence base that would guide patient counseling, selection, and lead to improved outcomes.

Do Gut Hormones Contribute to Weight Loss and Glycaemic Outcomes after Bariatric Surgery?

Bariatric surgery is an effective intervention for management of obesity through treating dysregulated appetite and achieving long-term weight loss maintenance. Moreover, significant changes in glucose homeostasis are observed after bariatric surgery including, in some cases, type 2 diabetes remission from the early postoperative period and postprandial hypoglycaemia. Levels of a number of gut hormones are dramatically increased from the early period after Roux-en-Y gastric bypass and sleeve gastrectomy—the two most commonly performed bariatric procedures—and they have been suggested as important mediators of the observed changes in eating behaviour and glucose homeostasis postoperatively. In this review, we summarise the current evidence from human studies on the alterations of gut hormones after bariatric surgery and their impact on clinical outcomes postoperatively. Studies which assess the role of gut hormones after bariatric surgery on food intake, hunger, satiety and glucose homeostasis through octreotide use (a non-specific inhibitor of gut hormone secretion) as well as with exendin 9–39 (a specific glucagon-like peptide-1 receptor antagonist) are reviewed. The potential use of gut hormones as biomarkers of successful outcomes of bariatric surgery is also evaluated.

The neuroscience of sugars in taste, gut-reward, feeding circuits, and obesity

Throughout the animal kingdom sucrose is one of the most palatable and preferred tastants. From an evolutionary perspective, this is not surprising as it is a primary source of energy. However, its overconsumption can result in obesity and an associated cornucopia of maladies, including type 2 diabetes and cardiovascular disease. Here we describe three physiological levels of processing sucrose that are involved in the decision to ingest it: the tongue, gut, and brain. The first section describes the peripheral cellular and molecular mechanisms of sweet taste identification that project to higher brain centers. We argue that stimulation of the tongue with sucrose triggers the formation of three distinct pathways that convey sensory attributes about its quality, palatability, and intensity that results in a perception of sweet taste. We also discuss the coding of sucrose throughout the gustatory pathway. The second section reviews how sucrose, and other palatable foods, interact with the gut-brain axis either through the hepatoportal system and/or vagal pathways in a manner that encodes both the rewarding and of nutritional value of foods. The third section reviews the homeostatic, hedonic, and aversive brain circuits involved in the control of food intake. Finally, we discuss evidence that overconsumption of sugars (or high fat diets) blunts taste perception, the post-ingestive nutritional reward value, and the circuits that control feeding in a manner that can lead to the development of obesity.

Prospective study of gut hormone and metabolic changes after laparoscopic sleeve gastrectomy and Roux-en-Y gastric bypass

Background

Laparoscopic sleeve gastrectomy (SG) has surpassed Roux-en-Y gastric bypass (RYGB) as the most prevalent bariatric procedure worldwide. While RYGB and SG demonstrate equivalent short-term weight loss, long-term weight loss tends to be greater after RYGB. Differences in the effect of these procedures on gastrointestinal hormones that regulate energy homeostasis are felt to partially underlie differences in outcomes. The objective of this study was to prospectively quantify blood levels of gut hormones of energy and glucose homeostasis at one year follow up to delineate possible reasons for greater efficacy of RYGB over SG in achieving weight loss.

Methods

Patients undergoing SG (n = 19) and RYGB (n = 40) were studied before surgery and at 2,12, 26, and 52 weeks postoperatively. Blood samples drawn in the fasted state and after a liquid mixed meal were assayed at baseline, 26, and 52 weeks for peptide YY (PYY), glucagon-like peptide-1 (GLP-1), ghrelin, insulin, glucose, and leptin. Fasting and postprandial appetitive sensations were assessed by visual analog scale.

Results

At 1 year there was greater weight loss in RYGB compared with SG patients (30% vs 27%; P = 0.03). Area under the curve (AUC) after the mixed meal for PYY was greater in RYGB patients (P<0.001). RYGB patients had significant increases in GLP-1 AUC compared to baseline (P = 0.002). Ghrelin levels decreased only after SG compared to baseline (P<0.001) but were not significantly different from RYGB. There was a trend toward decreased sweet cravings in RYGB patients (P = 0.056).

Conclusions

Differences in gastrointestinal hormones that regulate energy and glucose homeostasis are a possible mechanism for greater efficacy of RYGB compared to SG.

Revisiting the Ghrelin Changes Following Bariatric and Metabolic Surgery

Since the description of ghrelin in 1999, several studies have dug into the effects of this hormone and its relationship with bariatric surgery. While some aspects are still unresolved, a clear connection between ghrelin and the changes after metabolic surgery have been established. Besides weight loss, a significant amelioration in obesity-related comorbidities following surgery has also been reported. These changes in patients occur in the early postoperative period, before the weight loss appears, so that amelioration may be mainly due to hormonal changes. The purpose of this review is to go through the current body of knowledge of ghrelin's physiology, as well as to update and clarify the changes that take place in ghrelin concentrations following bariatric/metabolic surgery together with their potential consolidation to outcomes.

Emerging role of GIP and related gut hormones in fertility and PCOS

Gastric inhibitory polypeptide (GIP) is best known as an incretin hormone released by enteroendocrine K-cells in response to feeding and stimulates insulin release to regulate blood glucose and nutrient homeostasis. More recently GIP has been ascribed a positive role in lipid metabolism, bone strength, cardiovascular function and cognition. The present paper considers an emerging role of GIP and related gut hormones in fertility and especially polycystic ovarian syndrome (PCOS). Key evidence concerns restoration of fertility in women with gross obesity and PCOS following bariatric surgery. This is considered to reflect indirect effects mediated by alleviation of insulin resistance together with possible direct effects of surgically induced changes of GIP, GLP-1 and related peptide hormones on ovaries and the hypothalamic-pituitary-adrenal axis. Further studies are required to determine inter-relationships between the hormones and cellular mechanisms involved but these observations suggest that GIP and other gut may provide a novel therapeutic approach for PCOS and other reproductive disorders.