Mechanisms of Action of Bariatric Surgery on Body Weight Regulation

Bariatric surgery is an effective treatment modality for obesity and obesity-associated complications. Weight loss after bariatric surgery was initially attributed to anatomic restriction or reduced energy absorption, but now it is understood that surgery treats obesity by influencing the subcortical areas of the brain to lower adipose tissue mass. There are three major phases of this process: initially the weight loss phase, followed by a phase where weight loss is maintained, and in a subset of patients a phase where weight is regained. These phases are characterized by altered appetitive behavior together with changes in energy expenditure. The mechanisms associated with the rearrangement of the gastrointestinal tract include central appetite control, release of gut peptides, change in microbiota and bile acids. However, the exact combination and timing of signals remain largely unknown.

Hepatic lipid-associated macrophages mediate the beneficial effects of bariatric surgery against MASH

For patients with obesity and metabolic syndrome, bariatric procedures such as vertical sleeve gastrectomy (VSG) have a clear benefit in ameliorating metabolic dysfunction-associated steatohepatitis (MASH). While the effects of bariatric surgeries have been mainly attributed to nutrient restriction and malabsorption, whether immuno-modulatory mechanisms are involved remains unclear. Here we report that VSG ameliorates MASH progression in a weight loss-independent manner. Single-cell RNA sequencing revealed that hepatic lipid-associated macrophages (LAMs) expressing the triggering receptor expressed on myeloid cells 2 (TREM2) increase their lysosomal activity and repress inflammation in response to VSG. Remarkably, TREM2 deficiency in mice ablates the reparative effects of VSG, suggesting that TREM2 is required for MASH resolution. Mechanistically, TREM2 prevents the inflammatory activation of macrophages and is required for their efferocytotic function. Overall, our findings indicate that bariatric surgery improves MASH through a reparative process driven by hepatic LAMs, providing insights into the mechanisms of disease reversal that may result in new therapies and improved surgical interventions.

Severe Anemia in Sprague-Dawley Rats After Roux-en-Y Gastric Bypass Surgery

Roux-en-Y gastric bypass (RYGB) surgery is one of the most commonly performed bariatric procedures for weight loss in humans. However, this procedure is not risk-free, and patients may experience complications that include small bowel obstruction, gastrointestinal bleeding, chronic diarrhea, ulcers, malnutrition, and anemia. In particular, anemia is a recognized long-term complication and can be severe. Rats have been used as a model to study the effects of gastric bypass surgeries. They can experience similar complications as people, but the development of severe anemia has not previously been reported in rats. We observed 2 cases of severe anemia in female Sprague-Dawley rats after RYGB surgery. These cases prompted us to further investigate the frequency and severity of anemia after RYGB in rats. Blood work and necropsies were performed on 9 additional female Sprague-Dawley rats (5 with RYGB, 4 with sham surgery). In these 9 rats, only one had signs of clinical anemia. These 3 anemic rats displayed moderate to severe pallor of the eyes and ears. Necropsy findings in anemic RYGB rats included pale internal organs and eccentric heart enlargement, which led to a significantly higher heart:body weight ratio in RYGB rats as compared with sham controls. Anemic rats had either a macrocytic normochromic anemia, consistent with vitamin B12 or folate deficiency, or microcytic hypochromic anemia, indicative of iron deficiency. Researchers who perform RYGB surgery in rats should be aware of the potential complication of severe anemia. Plans for the diagnosis and management of this complication and the development of criteria for humane endpoints for severe anemia are recommended as a refinement to these studies.

Finding balance: understanding the energetics of time-restricted feeding in mice

Over the course of mammalian evolution, the ability to store energy likely conferred a survival advantage when food became scarce. A long-term increase in energy storage results from an imbalance between energy intake and energy expenditure, two tightly regulated parameters that generally balance out to maintain a fairly stable body weight. Understanding the molecular determinants of this feat likely holds the key to new therapeutic development to manage obesity and associated metabolic dysfunctions. Time-restricted feeding (TRF), a dietary intervention that limits feeding to the active phase, can prevent and treat obesity and metabolic dysfunction in rodents fed a high-fat diet, likely by exerting effects on energetic balance. Even when body weight is lower in mice on active-phase TRF, food intake is generally isocaloric as compared with ad libitum fed controls. This discrepancy between body weight and energy intake led to the hypothesis that energy expenditure is increased during TRF. However, at present, there is no consensus in the literature as to how TRF affects energy expenditure and energy balance as a whole, and the mechanisms behind metabolic adaptation under TRF are unknown. This review examines our current understanding of energy balance on TRF in rodents and provides a framework for future studies to evaluate the energetics of TRF and its molecular determinants.

Suboptimal Weight Loss 13 Years After Roux-en-Y Gastric Bypass: Is Hedonic Hunger, Eating Behaviour and Food Reward to Blame?

Purpose

Suboptimal weight loss (SWL) and weight regain (WR) following bariatric surgery are common. The exact reasons for this phenomenon remain to be fully elucidated. To compare hedonic hunger, food preferences, food reward and eating behaviour traits between participants with SWL and optimal weight loss (OWL) 13 years after Roux-en-Y gastric bypass (RYGB).

Materials and Method

Cross-sectional case control study where participants experiencing SWL or OWL (< or ≥ 50% of excess weight, respectively) post-RYGB were compared to a non-surgical control group matched for pre-operative body mass index. Hedonic hunger (Power of Food Scale), implicit and explicit liking and wanting for high-fat and low-fat savoury and sweet food (Leeds Food Preference Questionnaire) and eating behaviour (Dutch Eating Behavior Questionnaire, Three-Factor Eating Questionnaire and the Food Cravings Questionnaires State and Trait-reduced) were assessed.

Results

In total, 75 participants were recruited from the bariatric surgery observation study (BAROBS). Disinhibition, hunger, emotional, external and restrained eating, frequency of cravings and hedonic hunger were lower in the OWL, compared with the SWL and/or control groups. Implicit wanting and explicit liking and wanting for high-fat savoury and high-fat sweet food were lower, and implicit wanting for low-fat savoury food higher, in the OWL, compared with the SWL and/or control groups.

Conclusion

SWL 13 years after RYGB is associated with dysfunctional eating behaviours, increased preference and reward for high-fat food and increased hedonic hunger. Future longitudinal studies are needed to establish the cause-effect relationship between these variables.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s11695-022-06075-z.

Diet and physical activity are associated with suboptimal weight loss and weight regain 10-15 years after Roux-en-Y gastric bypass: A cross-sectional study

INTRODUCTION

Suboptimal weight loss (SWL) after bariatric surgery affects approximately 30% of the patients in the long-term. Diet and physical activity (PA) are likely to modulate long term weight loss outcomes after Roux-en-Y gastric bypass (RYGB).

OBJECTIVES

To compare food habits and PA levels between those experiencing SWL and optimal weight loss (OWL), and between those experiencing weight regain (WR) and no weight regain (NWR), 10-15 years after RYGB, in addition to a pre-operative control group.

METHODS

Participants were recruited from the Bariatric Surgery Observation Study (BAROBS), ≥ 10 y after RYGB. Food intake was assessed by a Food Frequency Questionnaire (FFQ) and PA levels with Sensewear armbands.

RESULTS

75 participants (79% females) were recruited. Excess weight loss (EWL) was 17 ± 19% and 87 ± 22% in the SWL and OWL groups, respectively and WR was 31 ± 15% and 1 ± 11% in the WR and NWR groups, respectively (P < 0.001 for both). The OWL group reported a lower energy intake (P = 0.012) than the control group. The control group reported a higher intake of milk, cream and cheese than both SWL group (P = 0.008) and OWL group (P < 0.001). The SWL group reported a higher intake of processed meat products than the OWL group, while the OWL group reported a lower intake of sauces than both the SWL and the control groups (P < 0.001 and P = 0.005, respectively). The OWL group reported a lower intake of cakes, sugar and sweets than both SWL group (P = 0.035) and control group (P = 0.021). The WR group reported a lower PA duration (P = 0.046) compared with the NWR group. EWL was positively, and WR negatively, correlated with average PA duration.

CONCLUSION

A high intake of energy-dense foods and low PA is associated with poor weight loss outcomes, namely SWL and WR, 10-15 years after RYGB.

The Influence of Roux-en-Y Gastric Bypass and Diet on NaCl and Sucrose Taste Detection Thresholds and Number of Circumvallate and Fungiform Taste Buds in Female Rats

Roux-en-Y gastric bypass (RYGB) in rats attenuates preference for, and intake of, sugar solutions. Additionally, maintenance on a high-fat diet (HFD) reportedly alters behavioral responsiveness to sucrose in rodents in short-term drinking tests. Due to the fact that the behavioral tests to date rely on the hedonic value of the stimulus to drive responsiveness, we sought to determine whether taste detection thresholds to sucrose and NaCl are affected by these manipulations as measured in an operant two-response signal detection paradigm. Female rats were maintained on HFD or chow for 10 weeks, at which point animals received either RYGB or SHAM surgery followed by a gel-based diet and then powdered chow. Upon recovery, half of the rats that were previously on HFD were switched permanently to chow, and the other rats were maintained on their presurgical diets (n = 5–9/diet condition x surgery group for behavioral testing). The rats were then trained and tested in a gustometer. There was a significant interaction between diet condition and surgery on NaCl threshold that was attributable to a lower value in RYGB vs. SHAM rats in the HFD condition, but this failed to survive a Bonferroni correction. Importantly, there were no effects of diet condition or surgery on sucrose thresholds. Additionally, although recent evidence suggests that maintenance on HFD alters taste bud number in the circumvallate papillae (CV) of mice, in a subset of rats, we did not find that diet significantly influenced taste pores in the anterior tongue or CV of female rats. These results suggest that any changes in sucrose responsiveness in intake/preference or hedonically oriented tests in rats as a function of HFD maintenance or RYGB are not attributable to alterations in taste sensitivity.

Gut HIF2α signaling is increased after VSG, and gut activation of HIF2α decreases weight, improves glucose, and increases GLP-1 secretion

Gastric bypass and vertical sleeve gastrectomy (VSG) remain the most potent and durable treatments for obesity and type 2 diabetes but are also associated with iron deficiency. The transcription factor HIF2α, which regulates iron absorption in the duodenum, increases following these surgeries. Increasing iron levels by means of dietary supplementation or hepatic hepcidin knockdown does not undermine the effects of VSG, indicating that metabolic improvements following VSG are not secondary to lower iron levels. Gut-specific deletion of Vhl results in increased constitutive duodenal HIF2α signaling and produces a profound lean, glucose-tolerant phenotype that mimics key effects of VSG. Interestingly, intestinal Vhl deletion also results in increased intestinal secretion of GLP-1, which is essential for these metabolic benefits. These data demonstrate a role for increased duodenal HIF2α signaling in regulating crosstalk between iron-regulatory systems and other aspects of systemic physiology important for metabolic regulation.

Bariatric surgery remains the most potent treatment for obesity and type 2 diabetes but also reduces iron levels. Evers et al. find that the machinery for absorbing iron is activated after VSG. Activation of this machinery recapitulates multiple effects of VSG. These findings may lead to less invasive therapies.

Determinants of eating behaviour in Black, Asian and Minority Ethnic (BAME) university students when living at and away from home: With a focus on the influence of food enculturation and food acculturation

For some students, university, can be a period of increased autonomy in food choice and for black, Asian and minority ethnic (BAME) and international students, the addition of culture may be a governing factor. This study aimed to examine the extent of dietary acculturation and dietary enculturation on the influence of student's food choices using a phenomenological approach. Sixty participants (forty-one home students and nineteen international students) recruited by purposive sampling, were included in the study. Data collection involved self-administered multiple choice and short answer questionnaires and semi structured interviews. The results were analysed using thematic analysis. When living away from home, six major themes influenced the eating behaviour of the studied population: social environment, individual factors, physical environment, university life, enculturation and acculturation. When at home, five major themes were influential: social environment, individual factors, physical environment, enculturation and acculturation. The main findings suggest dietary enculturation is a factor which influences the dietary behaviour of both international students and BAME home students.

The Role of Elevated Branched-Chain Amino Acids in the Effects of Vertical Sleeve Gastrectomy to Reduce Weight and Improve Glucose Regulation

Elevated levels of branched-chain amino acids (BCAAs) and their metabolites are strongly positively associated with obesity, insulin resistance, and type 2 diabetes. Bariatric surgery is among the best treatments for weight loss and associated morbidities. Clinical studies have reported that bariatric surgery decreases the circulating levels of BCAAs. The objective of this study was to test the hypothesis that reduced BCAA levels contribute to the metabolic improvements of sustained weight loss and improved glucose tolerance after vertical sleeve gastrectomy (VSG). We find that, as in humans, circulating BCAAs are significantly lower in VSG rats and mice. To increase circulating BCAAs, we tested mice with either increased dietary intake of BCAAs or impaired BCAA catabolism by total body deletion of mitochondrial phosphatase 2C (Pp2cm). Our results show that a decrease in circulating BCAAs is not necessary for sustained body weight loss and improved glucose tolerance after VSG.

Increased branched-chain amino acid (BCAA) levels are biomarkers of metabolic disease, and bariatric surgeries reduce BCAA levels. Bozadjieva Kramer et al. show that both dietary and genetic manipulations can block the surgical effect on BCAAs but do not alter potent, beneficial effects on weight loss and glucose tolerance.

Food Preferences and Their Perceived Changes Before and After Bariatric Surgery: a Cross-sectional Study

PURPOSE

Changes in food preferences, taste, and smell following bariatric surgery have been previously described but with inconsistent results. We aimed to describe current food preferences and their perceived changes before and after the surgery. We further compared food preferences between patients with and without taste or smell alterations, before and above 2 years follow-up, and concerning the success or failure of their surgery.

MATERIALS AND METHODS

This cross-sectional study was conducted with a self-administered online questionnaire. Two years was the cut-off between short- and long-term follow-up. Success was defined as an excess weight loss (EWL) greater or equal to 50%.

RESULTS

In total, 220 postoperative patients answered the questionnaire. Patients with taste alterations (64%) had significantly lower preferences for red meat, milk, cheese, desserts, fried foods, and water (all p < 0.05) relative to the non-taste alteration group, while those with smell alterations (38%) had significantly lower preference for cheese only (p < 0.05) relative to the non-smell alteration group. Patients with a ≥ 2-year follow-up had a higher liking for desserts, fried foods, fat, bread, hot drinks, and alcohol compared to patients with a < 2-year follow-up (all p < 0.05). Patients having success in surgery had higher liking scores for green vegetables and lower liking scores for starchy foods, milk, and sweet dairy products (all p < 0.05).

CONCLUSIONS

Our study suggests that patients who underwent bariatric surgery have different food preference patterns according to their sensory perceptions, the duration of their follow-up, and the success of bariatric surgery.

A Pilot Study of Gut-Brain Signaling After Octreotide Therapy for Unintentional Weight Loss After Esophagectomy

BACKGROUND

Recurrence-free patients after esophageal cancer surgery face long-term nutritional consequences, occurring in the context of an exaggerated postprandial gut hormone response. Acute gut hormone suppression influences brain reward signaling and eating behavior. This study aimed to suppress gut hormone secretion and characterize reward responses and eating behavior among postesophagectomy patients with unintentional weight loss.

METHODS

This pilot study prospectively studied postoperative patients with 10% or greater body weight loss (BWL) beyond 1 year who were candidates for clinical treatment with long-acting octreotide (LAR). Before and after 4 weeks of treatment, gut hormone secretion, food cue reactivity (functional magnetic resonance imaging), eating motivation (progressive ratio task), ad libitum food intake, body composition, and symptom burden were assessed.

RESULTS

Eight patients (7 male, age: mean ± SD 62.8 ± 9.4 years, postoperative BWL: 15.5 ± 5.8%) participated. Octreotide LAR did not significantly suppress total postprandial plasma glucagon-like peptide-1 response at 4 weeks (P = .08). Postprandial symptom burden improved after treatment (Sigstad score median [range]: 12 [2-28] vs 8 [3-18], P = .04) but weight remained stable (pre: 68.6 ± 12.8 kg vs post: 69.2 ± 13.4 kg, P = .13). There was no significant change in brain reward system responses, during evaluation of high-energy or low-energy food pictures, nor their appeal rating. Moreover, treatment did not alter motivation to eat (P = .41) nor ad libitum food intake(P = .46).

CONCLUSION

The protocol used made it feasible to characterize the gut-brain axis and eating behavior in this cohort. Inadequate suppression of gut hormone responses 4 weeks after octreotide LAR administration may explain the lack of gut-brain pathway alterations. A higher dose or shorter interdose interval may be required to optimize the intervention.

Effect of bariatric surgery on circulating FGF-19: A systematic review and meta-analysis

Fibroblast growth factor-19 (FGF-19) is a gut hormone which interacts with metabolism and is depleted in obesity. There is some indication that the hormone undergoes a resurgence following bariatric surgery (BS), an effect which may contribute to the beneficial outcomes of such procedures. This systematic review and meta-analysis aims to synthesize the available literature on FGF-19 levels before and after BS. MEDLINE, Scopus and Web of Science databases were searched, and the effect of different surgical procedures and degrees of body mass index (BMI) reduction on FGF-19 levels was assessed by DerSimonian and Laird random-effects model in meta-analysis and dose-response analyses. This meta-analysis, which included 474 patients from 25 arms undergoing one of five BS procedures, revealed a significant increase in the levels of circulating FGF-19 following all-type BS. Vertical sleeve gastrectomy, duodenal-jejunal bypass liner and Roux-en-Y gastric bypass all significantly increased circulating FGF-19 levels from baseline. However, gastric banding failed to achieve the same, and in fact, biliopancreatic diversion was associated with decreased circulating FGF-19. Finally, an inverse association between FGF-19 and the degree of BMI-reduction post-operatively was noted. FGF-19 is increased by BS and may represent a pharmaceutical target in efforts to reproduce the beneficial effects of BS in a medical setting.

Binge eating scores pre-bariatric surgery and subsequent weight loss: A prospective, 5 years follow-up study

BACKGROUND & AIMS

To compare groups of bariatric patients with preoperative scores of Binge Eating Scale (BES) above and below the clinical cut off value on weight outcomes up to 60 months following surgery.

METHODS

This is a prospective observational study involving 108 Brazilian patients (follow-up rate: 48.1%) operated by Roux-en-Y gastric bypass. In the preoperative period, they were clinically evaluated, and BES was applied. Based on the scores, patients were categorized as high or low according to established cut off 17 for binge eaters. Follow-up weight loss was obtained (3, 6, 12, 24, 36, 48, and 60 months) using data from medical records. The percentage of total weight loss (%TWL) was examined by generalized linear model.

RESULTS

41.7% of patients had BES scores higher than 17 at baseline. Weight loss was significant up to 12 months. The greatest weight loss was at 24 months of follow-up, ranging from 2.7 to 110.4 kg (mean 42.9 ± 17.8 kg). In the short postoperative period (3, 24, and 36 months), %TWL was significantly different between groups. At 24 months, patients with higher scores lost more %TWL than those with lower scores (35.1 ± 0.8% vs 31.6 ± 0.7%, p = 0.029). However, this difference was not fount at 60 months postoperatively (mean 28.9 ± 9.6%). In a multivariate analysis, the presence of depression, age, and BES score were not associated with %TWL at 24 and 60 months.

CONCLUSIONS

The results suggest that preoperative BES scores point to a similar weight loss after bariatric surgery. Further studies with long-term follow-up are necessary to evaluate this finding.

Changes in Frequency Intake of Foods in Patients Undergoing Sleeve Gastrectomy and Following a Strict Dietary Control

PURPOSE

Dietary intake and food preferences change after bariatric surgery, secondary to gastrointestinal symptoms and dietitian counseling. The aim of this study was to evaluate the changes in the frequency intake of different foods in patients undergoing sleeve gastrectomy and following a strict dietary control.

PATIENTS AND METHODS

A prospective observational study of all the morbidly obese patients undergoing laparoscopic sleeve gastrectomy as bariatric procedure between 2007 and 2012 was performed. Dietary assessment was performed using the Alimentary Frequency Questionnaire 1991-2002, developed and validated by the Department of Epidemiology of Miguel Hernandez University (Elche, Alicante Spain).

RESULTS

Ninety-three patients were included for analysis, 73 females and 20 males, with a mean preoperative BMI of 46.4 ± 7.9 kg/m². One year after surgery, excess weight loss was 81.1 ± 8.3% and 5 years after surgery, 79.9 ± 6.4%. Total weight loss at 1 year was 38.8 ± 5.3% and at 5 years, 35.4 ± 4.9%. Postoperatively, a reduction in the intake of dairy products, red meat, deli meat products, shellfish, fried potatoes, sweets, rice, pasta, beer, and processed foods was observed. Vegetables, fruits, and legumes intake increased after surgery. In the first postoperative year, there was a slight intolerance to red meat, fruits, vegetables and legumes, dairy products, pasta, and rice that mostly disappeared 5 years after surgery.

CONCLUSION

One year after sleeve gastrectomy, calibrated with a 50-French bougie, there are not important problems in the intake of foods a priori difficult to digest. These problems mostly disappeared 5 years after surgery. The decrease intake of other unhealthy foods is mostly based on the dietary counseling.

Effect of Macronutrient Type and Gastrointestinal Release Site on PYY Response in Normal Healthy Subjects

BACKGROUND AND AIMS

Enteroendocrine L cells release satiety inducing hormones in response to stimulation by luminal macronutrients. We sought to profile the differential effect of macronutrient type and site of release on circulating concentrations of the L cell-derived enteroendocrine hormone peptide tyrosine tyrosine (amino acids 1 to 36) (PYY).

MATERIALS AND METHODS

Eight healthy volunteers were recruited to a randomized, double-blinded, six-way crossover study. At each visit, the participants consumed a 500-kcal drink containing carbohydrate, protein, or fat in either gastric or small intestinal release formulations. Plasma PYY concentrations and hunger ratings were assessed for 3 hours after consumption of the test drink. The food intake was recorded thereafter at an ad libitum lunch.

RESULTS

Microcapsular formulations targeting the distal small intestinal delivery of fat, but not carbohydrate or protein, markedly enhance PYY release relative to macronutrient delivery in gastric release formulations. Food intake at an ad libitum meal was lowest after consumption of the formulation releasing fat at the distal small intestine.

CONCLUSION

Targeting of fat to the distal small intestine in delayed release microcapsules enhanced PYY release and was associated with reductions in food intake.

Effects of Roux-en-Y Gastric Bypass and Sleeve Gastrectomy on Food Preferences and Potential Mechanisms Involved

PURPOSE OF REVIEW

Bariatric surgery leads to a substantial decrease in energy intake. It is unclear whether this decrease in energy intake is simply due to eating smaller portions of the same food items or a shift in food preference towards less energy-dense foods. This review evaluates the existing literature on changes in food preferences after bariatric surgery and the potential mechanisms involved.

RECENT FINDINGS

Changes in food preferences have been reported; however, the evidence is mainly based on indirect measurements, such as self-reporting. When changes in food preferences are directly assessed, results contradict previous findings, indicating that results based on self-reporting must be interpreted with caution as they do not necessarily reflect actual behaviour. However, it seems that there could be inter-individual differences in the response to surgery. Future studies investigating changes in food preferences should not only focus on direct measured of behaviour but should also consider the heterogeneity of the response after bariatric surgery.

The pros and cons of gastric bypass surgery - The role of the Roux-limb

The prevalence of overweight and obesity has exploded in the post-industrial era. Life style interventions like dieting and exercise can induce a marked weight loss, but the main problem for most patients is to maintain the reduced body weight over time. Gastric bypass surgery is a commonly performed and very effective method for achieving a pronounced and sustained weight loss including metabolic improvements in obese patients. Despite the therapeutic successfulness there are known side-effects like chronic postprandial nausea and pain that in some patients become intractable. The pathophysiology is complex and partly unexplored. The physician or surgeon handling a patient with "post-bariatric symptoms" must be aware of the risk for symptom aggravations due to iatrogenic opioid-associated intestinal dysmotility. The present paper gives a brief overview of obesity surgery and its associated postsurgical conditions with a focus on the unexplored role of the Roux-limb following gastric bypass surgery.

Meal patterns after bariatric surgery in mice and rats

With behavioral and pharmacological interventions continuously failing to tackle the obesity epidemic, bariatric surgery has been hailed as the most effective treatment strategy. Current literature suggests that bariatric surgery successfully decreases body weight and excess fat mass through targeting both variables of the energy homeostasis - energy intake and energy expenditure. Here we review current knowledge on changes in caloric consumption, an important arm in the energy balance equation, in rodent models of bariatric surgery. In particular, circadian feeding dynamics, post-surgical caloric intake at both "rapid weight loss" phase and "weight maintenance" phase, as well as meal pattern analysis will be the subject of this review. Considering that different types of bariatric surgery may trigger differential energy intake dynamics resulting in variable weight loss outcomes, the effects of most popular surgeries - vertical sleeve gastrectomy (VSG), Roux-en-Y gastric bypass (RYGB), and gastric banding (GB) - are elaborated. Potential candidate mechanisms underlying alterations in food intake and meal patterns following different bariatric procedures are briefly discussed at the end.

Associations between Weight Loss, Food Likes, Dietary Behaviors, and Chemosensory Function in Bariatric Surgery: A Case-Control Analysis in Women

We tested the hypothesis that successful weight loss post-bariatric surgery would be associated with healthier chemosensory function, food likes, and dietary behaviors than either unsuccessful weight loss or pre-surgery morbid obesity. In a case-control design, pre-surgical women with morbid obesity (n = 49) were compared with those 1-year post-surgery (24 Roux-en-Y Bypass, 24 Sleeve Gastrectomy) and defined by excess or percent weight loss as successful/unsuccessful. For self-reported smell/taste perception, more post-surgery than pre-surgery reported improved/distorted perception, especially if weight loss successful. Measured taste function (perceived quinine and NaCl intensity) was lower among weight loss unsuccessful versus pre-surgery patients, yet a genetic variation in taste probe (propylthiouracil bitterness) matched expected frequencies without significant pre/post-surgery difference. Regarding survey-reported liking, higher diet quality was seen in the weight loss successful (independent of surgery type) versus pre-surgical patients, with differences driven by lower sweet and refined carbohydrate liking. The post versus pre-surgical patients had greater restraint but less hunger and disinhibition. Patients reporting both higher diet quality and lower hunger showed greater % weight loss, independent of surgery type. Thus, successful weight loss 1-year post-bariatric surgery was associated with improved or distorted chemosensation and patterns of liking associated with healthier diets, especially if coupled with less hunger.

Regulation of intestinal growth in response to variations in energy supply and demand

The growth of the intestine requires energy, which is known to be met by catabolism of ingested nutrients. Paradoxically, during whole body energy deficit including calorie restriction, the intestine grows in size. To understand how and why this happens, we reviewed data from several animal models of energetic challenge. These were bariatric surgery, cold exposure, lactation, dietary whey protein intake and calorie restriction. Notably, these challenges all reduced the adipose tissue mass, altered hypothalamic neuropeptide expression and increased intestinal size. Based on these data, we propose that the loss of energy in the adipose tissue promotes the growth of the intestine via a signalling mechanism involving the hypothalamus. We discuss possible candidates in this pathway including data showing a correlative change in intestinal (ileal) expression of the cyclin D1 gene with adipose tissue mass, adipose derived-hormone leptin and hypothalamic expression of leptin receptor and the pro-opiomelanocortin gene. The ability of the intestine to grow in size during depletion of energy stores provides a mechanism to maximize assimilation of ingested energy and in turn sustain critical functions of tissues important for survival.

Impact of gastric emptying and small intestinal transit on blood glucose, intestinal hormones, glucose absorption in the morbidly obese

This study evaluated gastric emptying (GE) and small intestinal (SI) transit in people with morbid obesity and their relationships to glycaemia, incretin hormones, and glucose absorption METHODS: GE and caecal arrival time (CAT) of a mixed meal were assessed in 22 morbidly obese (50.2 ± 2.5 years; 13 F:9 M; BMI: 48.6 ± 1.8 kg/m²) and 10 lean (38.6 ± 8.4 years; 5 F:5 M; BMI: 23.9 ± 0.7 kg/m²) subjects, using scintigraphy. Blood glucose, plasma 3-O-methylglucose, insulin, glucagon, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) were measured. Insulin sensitivity and resistance were also quantified RESULTS: When compared with lean subjects, GE (t50: 60.7 ± 6.5 vs. 41.1 ± 7.3 min; P  = 0.04) and CAT (221.5 ± 9.8 vs. 148.0 ± 7.1 min; P =  0.001) of solids were prolonged in morbid obesity. Postprandial rises in GIP (P = 0.001), insulin (P  = 0.02), glucose (P = 0.03) and 3-O-methylglucose (P = 0.001) were less. Whereas GLP-1 increased at 45 mins post-prandially in lean subjects, there was no increase in the obese (P  = 0.04). Both fasting (P = 0.045) and postprandial (P = 0.012) plasma glucagon concentrations were higher in the obese CONCLUSIONS: GE and SI transit are slower in the morbidly obese, and associated with reductions in postprandial glucose absorption, and glycaemic excursions, as well as plasma GIP and GLP-1.

Targeting FXR and FGF19 to Treat Metabolic Diseases-Lessons Learned From Bariatric Surgery

Bariatric surgery procedures, such as Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG), are the most effective interventions available for sustained weight loss and improved glucose metabolism. Bariatric surgery alters the enterohepatic bile acid circulation, resulting in increased plasma bile levels as well as altered bile acid composition. While it remains unclear why both VSG and RYGB can alter bile acids, it is possible that these changes are important mediators of the effects of surgery. Moreover, a molecular target of bile acid synthesis, the bile acid-activated transcription factor FXR, is essential for the positive effects of VSG on weight loss and glycemic control. This Perspective examines the relationship and sequence of events between altered bile acid levels and composition, FXR signaling, and gut microbiota after bariatric surgery. We hypothesize that although bile acids and FXR signaling are potent mediators of metabolic function, unidentified downstream targets are the main mediators behind the benefits of weight-loss surgery. One of these targets, the gut-derived peptide FGF15/19, is a potential molecular and therapeutic marker to explain the positive metabolic effects of bariatric surgery. Focusing research efforts on identifying these complex molecular mechanisms will provide new opportunities for therapeutic strategies to treat obesity and metabolic dysfunction.

Taste and odor preferences following Roux-en-Y surgery in humans

It is well established that bariatric surgery, the most effective method to achieve long-term weight loss in obese subjects, reverses enhanced preference and intake of sweet/fatty foods. Although taste and odor preference changes following bariatric surgery have been previously described, their time course and relationship to weight loss remains an issue. The aim of this study was to determine the relationship between taste and odor preference changes and successful weight loss following bariatric surgery. A cross-sectional study was performed on 195 human subjects with body mass index (BMI) above 30 (at least class I obesity), who were scheduled to receive (n = 54) or had previously received (n = 141) Roux-en-Y gastric bypass (RYGB). A Self-Assessment Manikin test was used to measure each participant’s affective reaction (ranging from pleasure to displeasure) to a variety of food-related and odor-related pictures. Results confirmed earlier reports about changes in sweet/fatty foods preference after surgery and revealed a shift in preference toward less calorie-dense foods. Relatedly, endorsements of “favorite” foods were mostly sweet/fatty foods in subjects awaiting surgery but were shifted toward more healthy choices, particularly vegetables, in subjects post-RYGB surgery. However, food preference ratings trended toward pre-surgical levels as the time since surgery increased. Answers to open-ended questions about why their diet changed post-surgery revealed that changes in cravings, rather than changes in taste per se, were the major factor. Surprisingly, patients rating a coffee taste as more pleasing after surgery had a lower post-surgical BMI. No associations of odors with change in BMI were apparent. Results showed that following bariatric surgery taste preferences are significantly altered and that these changes correlate with lowered BMI. However, these changes fade as time since surgery lengthens. These results may suggest diagnostic criteria to identify people at risk for less than optimal changes in BMI following bariatric surgery.

Weight loss decreases self-reported appetite and alters food preferences in overweight and obese adults: Observational data from the DiOGenes study

People with obesity often struggle to maintain their weight loss after a weight loss period. Furthermore, the effect of weight loss on appetite and food preferences remains unclear. Hence this study investigated the effect of weight loss on subjective appetite and food preferences in healthy, overweight and obese volunteers. A subgroup of adult participants (n = 123) from the Diet Obesity and Genes (DiOGenes) study (subgroup A) was recruited from across six European countries. Participants lost ≥8% of initial body weight during an 8-week low calorie diet (LCD). Subjective appetite and food preferences were measured before and after the LCD, in response to a standardized meal test, using visual analogue rating scales (VAS) and the Leeds Food Choice Questionnaire (FCQ). After the LCD, participants reported increased fullness (p < 0.05), decreased desire to eat (p < 0.05) and decreased prospective consumption (p < 0.05) after consuming the test meal. An interaction effect (visit x time) was found for hunger ratings (p < 0.05). Area under the curve (AUC) for hunger, desire to eat and prospective consumption was decreased by 18.1%, 20.2% and 21.1% respectively whereas AUC for fullness increased by 13.9%. Preference for low-energy products measured by the Food Preference Checklist (FPC) decreased by 1.9% before the test meal and by 13.5% after the test meal (p < 0.05). High-carbohydrate and high-fat preference decreased by 11.4% and 16.2% before the test meal and by 17.4% and 22.7% after the meal (p < 0.05). No other effects were observed. These results suggest that LCD induced weight loss decreases the appetite perceptions of overweight volunteers whilst decreasing their preference for high-fat-, high-carbohydrate-, and low-energy products.

Adolescent Loss-of-Control Eating and Weight Loss Maintenance After Bariatric Surgery

BACKGROUND

Loss-of-control (LOC) eating is common in adults undergoing bariatric surgery and is associated with poorer weight outcomes. Its long-term course in adolescent bariatric surgery patients and associations with weight outcomes are unclear.

METHODS

Adolescents (n = 234; age range = 13-19 years) undergoing bariatric surgery across 5 US sites were assessed for postsurgery follow-up at 6 months and 1, 2, 3, and 4 years. Descriptive statistics and generalized linear mixed models were used to describe the prevalence of LOC eating episodes involving objectively large amounts of food and continuous eating, respectively. Generalized linear mixed models investigated the association of any LOC eating with short- and long-term BMI changes.

RESULTS

At baseline, objectively large LOC eating was reported by 15.4% of adolescents, and continuous LOC eating by 27.8% of adolescents. Both forms of LOC eating were significantly lower at all postsurgical time points relative to presurgery (range = 0.5%-14.5%; Ps < .05). However, both behaviors gradually increased from 6-month to 4-year follow-up (Ps < .05). Presurgical LOC eating was not related to percent BMI change over follow-up (P = .79). However, LOC eating at 1-, 2-, and 3-year follow-up was associated with lower percent BMI change from baseline at the next consecutive assessment (Ps < .05).

CONCLUSIONS

Although presurgical LOC eating was not related to relative weight loss after surgery, postoperative LOC eating may adversely affect long-term weight outcomes. Rates of LOC eating decreased from presurgery to 6-months postsurgery but increased thereafter. Therefore, this behavior may warrant additional empirical and clinical attention.

Gut-Brain Cross-Talk in Metabolic Control

Because human energy metabolism evolved to favor adiposity over leanness, the availability of palatable, easily attainable, and calorically dense foods has led to unprecedented levels of obesity and its associated metabolic co-morbidities that appear resistant to traditional lifestyle interventions. However, recent progress identifying the molecular signaling pathways through which the brain and the gastrointestinal system communicate to govern energy homeostasis, combined with emerging insights on the molecular mechanisms underlying successful bariatric surgery, gives reason to be optimistic that novel precision medicines that mimic, enhance, and/or modulate gut-brain signaling can have unprecedented potential for stopping the obesity and type 2 diabetes pandemics.

Hypoparathyroidism after total thyroidectomy in patients with previous gastric bypass

PURPOSE

Case reports suggest that patients with previous gastric bypass have an increased risk of severe hypocalcemia after total thyroidectomy, but there are no population-based studies. The prevalence of gastric bypass before thyroidectomy and the risk of hypocalcemia after thyroidectomy in patients with previous gastric bypass were investigated.

METHODS

By cross-linking The Scandinavian Quality Registry for Thyroid, Parathyroid and Adrenal Surgery with the Scandinavian Obesity Surgery Registry patients operated with total thyroidectomy without concurrent or previous surgery for hyperparathyroidism were identified and grouped according to previous gastric bypass. The risk of treatment with intravenous calcium during hospital stay, and with oral calcium and vitamin D at 6 weeks and 6 months postoperatively was calculated by using multiple logistic regression in the overall cohort and in a 1:1 nested case-control analysis.

RESULTS

We identified 6115 patients treated with total thyroidectomy. Out of these, 25 (0.4 %) had undergone previous gastric bypass surgery. In logistic regression, previous gastric bypass was not associated with treatment with i.v. calcium (OR 2.05, 95 % CI 0.48-8.74), or calcium and/or vitamin D at 6 weeks (1.14 (0.39-3.35), 1.31 (0.39-4.42)) or 6 months after total thyroidectomy (1.71 (0.40-7.32), 2.28 (0.53-9.75)). In the nested case-control analysis, rates of treatment for hypocalcemia were similar in patients with and without previous gastric bypass.

CONCLUSION

Previous gastric bypass surgery was infrequent in patients undergoing total thyroidectomy and was not associated with an increased risk of postoperative hypocalcemia.

Potential Mechanisms Mediating Sustained Weight Loss Following Roux-en-Y Gastric Bypass and Sleeve Gastrectomy

Bariatric surgery is the only effective treatment for severe obesity. Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG), the most commonly performed procedures, lead to sustained weight loss, improvements in obesity-related comorbidities and reduced mortality. In humans, the main driver for weight loss following RYGB and SG is reduced energy intake. Reduced appetite, changes in subjective taste and food preference, and altered neural response to food cues are thought to drive altered eating behavior. The biological mediators underlying these changes remain incompletely understood but changes in gut-derived signals, as a consequence of altered nutrient and/or biliary flow, are key candidates.

Eating patterns and food choice as determinant of weight loss and improvement of metabolic profile after RYGB

OBJECTIVE

Significant changes in the preference for different dietary components have been observed after Roux-en-Y gastric bypass (RYGB). The aim of this study was to evaluate the early post-RYGB changes in quality of eating patterns and their relationship to weight loss and metabolic parameters.

METHODS

The sample was composed of 41 extremely obese individuals undergoing RYGB. Dietary data were collected using a validated food frequency questionnaire in Brazil. A food intake evaluation was conducted with a focus on the frequency of consumption (≥4 times/wk) of markers for healthy eating and markers for unhealthy eating. Furthermore, anthropometric and metabolic markers were collected before surgery and 6 mo post-RYGB.

RESULTS

Compared with baseline, the postsurgery body mass index was reduced by 12.9 kg/m², corresponding to an excess weight loss of 63.5%. Blood glucose, insulin, ferritin, cholesterol, low-density lipoprotein-cholesterol, triacylglycerol (TG), and hemoglobin were reduced 6 mo after RYGB (P < 0.05). The consumption frequency of many foods defined as unhealthy decreased after surgery (e.g., from 15.4% to 5.1% for pizza and 18% to 0% for hamburger), and some healthy food increased (e.g., from 0% to 5.1% for fish and from 0% to 25.6% for plain yogurt). There was a decrease in the frequency of individuals who reported consuming fruit and vegetables. Conversely, insulin, glucose, and TG levels were positively associated with intake of chocolates/truffles and ice cream/sundaes.

CONCLUSION

Participants in the present study appeared to develop a healthier dietary pattern by 6 mo after RYGB. These results show that a healthier dietary pattern is associated with a significant improvement of metabolic profile and weight loss.

Long-term Outcome after Robotic-assisted Gastroplication in Adolescents: Hunger Hormone and Food Preference Changes Two Case Reports

Weight loss surgery (WLS) is efficacious for long-term weight reduction and decreases overall mortality in severely obese patients. The mechanisms implicated in long-term weight loss are not fully understood. Proposed mechanisms include changes in gut hormones and brain regulation of appetite and satiety. We aimed to investigate the long-term ghrelin and leptin profiles and changes in food preference and eating behavior after WLS in adolescent patients. Two obese females aged 15 years and 14 4/12 years, who did not respond to lifestyle changes, including dietary intervention and physical exercise in combination with medical therapy, underwent robotic-assisted gastroplication. Anthropometric measurements, food habits and eating behavior, as well as metabolic and hormonal changes during long-term post-surgical follow-up were monitored. Long-term weight reduction was obtained in both patients, with a significant decrease in waist circumference. Resting energy expenditure showed a decrease over time, with a respiratory quotient that increased showing a shift from oxidation of a high-fat diet before surgery to oxidation of a mixed diet two and three years later. Both subjects improved their eating habits and lifestyle. Co-morbidity resolution was also noted. Increased pre-prandial ghrelin levels as well as higher post-prandial ghrelin and a leptin drop compared with pre-surgery values were observed in both patients. Persistent weight loss after gastroplication is associated with a favorable change in gut hormones and food preferences. The role of hormonal and sensory components in long-term results seems crucial. Particularly in adolescent patients, a multidisciplinary approach and continuous nutritional care is mandatory for weight maintenance and consolidation of changes.

Recent advances in the modification of taste and food preferences following bariatric surgery

There is a large body of evidence indicating that bariatric surgery provides durable weight loss and health benefits to patients who are obese and have comorbidities such as type 2 diabetes (T2D). However, there are still many questions related to mechanisms of metabolic improvement, predictors of success/failure, and long term consequences, which need to be answered. More recently, there has been a particular interest in the modulation of taste and food preferences that occurs after bariatric surgery and how this affects weight loss in different individuals. Animal models as well as human studies have shed some light on the role of taste in changing food preferences and how these changes may affect weight loss after surgery. The goal of this review is to discuss the physiological and behavioral consequences of bariatric surgery as a treatment for obesity and T2D, with particular emphasis on recent studies describing bariatric surgery-induced modifications in taste perception and food preferences.

Alterations in energy expenditure in Roux-en-Y gastric bypass rats persist at thermoneutrality

BACKGROUND

The compensatory decrease in energy expenditure (EE) in response to body weight loss is attenuated by Roux-en-Y gastric bypass (RYGB) surgery in rats. The thermoneutral zone (TNZ) is at higher temperatures in rodents than in humans. Consequently, rodents may be under moderate cold stress if EE is measured at room temperature, leading to increased EE due to adaptive thermogenesis. We speculated that the reported alterations in EE of RYGB rats at room temperature are caused by higher adaptive thermogenesis and are therefore not present at thermoneutrality.

METHODS

Male Wistar rats were randomized for RYGB or sham surgery. Some sham rats were body weight matched (BWM) to the RYGB rats by food restriction, the others received ad libitum access to food (AL). EE, body temperature, physical activity and food intake were measured at ambient temperatures between 22 and 32 °C to determine the TNZ. Adaptive thermogenesis requires β3-adrenergic receptor-mediated uncoupling protein-1 (UCP-1) expression in brown adipose tissue (BAT). The in vivo thermogenic capacity of BAT was determined by administering the β3-adrenergic agonist CL316,243, and UCP-1 protein expression was measured at room temperature.

RESULTS

The TNZ was between 28 and 30 °C for AL and RYGB and between 30 and 32 °C for BWM rats, respectively. In contrast to AL and BWM rats, EE was not significantly higher at room temperature than at thermoneutrality in RYGB rats, reflecting a lack of adaptive thermogenesis. Consistently, both the thermogenic capacity of BAT and UCP-1 expression were decreased in RYGB compared with AL rats at room temperature.

CONCLUSIONS

Our data confirm that the decrease in EE after body weight loss is attenuated by RYGB surgery and show that this effect persists at thermoneutrality. Contrary to our hypothesis, we found that adaptive thermogenesis at room temperature is reduced in RYGB rats.

The role of gut adaptation in the potent effects of multiple bariatric surgeries on obesity and diabetes

Bariatric surgical procedures such as vertical sleeve gastrectomy (VSG) and Roux-en-Y gastric bypass (RYGB) are the most potent treatments available to produce sustained reductions in body weight and improvements in glucose regulation. While traditionally these effects are attributed to mechanical aspects of these procedures, such as restriction and malabsorption, a growing body of evidence from mouse models of these procedures points to physiological changes that mediate the potent effects of these surgeries. In particular, there are similar changes in gut hormone secretion, bile acid levels, and composition after both of these procedures. Moreover, loss of function of the nuclear bile acid receptor (FXR) greatly diminishes the effects of VSG. Both VSG and RYGB are linked to profound changes in the gut microbiome that also mediate at least some of these surgical effects. We hypothesize that surgical rearrangement of the gastrointestinal tract results in enteroplasticity caused by the high rate of nutrient presentation and altered pH in the small intestine that contribute to these physiological effects. Identifying the molecular underpinnings of these procedures provides new opportunities to understand the relationship of the gastrointestinal tract to obesity and diabetes as well as new therapeutic strategies to harness the effectiveness of surgery with less-invasive approaches.