Effects of obesity surgery on food preferences, taste and reward in animals and humans

BACKGROUND: After Roux-en-Y gastric bypass bariatric surgery (RYGB) patients and animal models show a decreased preference for sweet/fatty foods. However, there are significant discrepancies in the findings of animal and human studies, and the mechanisms are not understood. AIMS: To investigate: 1. The effect of a high-fat (HFD) vs. low-fat (LFD) pre-operative maintenance diet on the ingestive behaviour of rats after RYGB 2. The effects of RYGB vs. gastric banding (BAND) surgery on food hedonics and brain reward systems in humans 3. The effects of RYGB on taste in humans METHODS: Study 1: Rats were fed either LFD or HFD before RYGB or sham surgery. Ingestive behaviour was assessed after surgery using food preference tests. Study 2: Brain reward responses to food were investigated using functional magnetic resonance imaging (fMRI), eating behaviour and metabolic phenotyping in body mass index (BMI) matched un-operated controls and patients after RYGB and BAND surgery. Study 3: The intensity and reward of sweet, fat and fat/sweet taste stimuli were assessed in patients undergoing RYGB using behavioural techniques. RESULTS: Study 1: Pre-operative maintenance diets with different fat contents, did not affect post-surgical weight loss or caloric intake. HFD-RYGB rats exhibited behaviour consistent with condition taste aversion to a familiar stimulus, compared to condition taste aversion to a novel stimulus in the LFD-RYGB rats. Study 2: Patients after RYGB had lower activation in brain reward systems to food and lower food hedonics than BAND patients and/or BMI-matched unoperated controls. Anorexigenic plasma gut hormones, plasma bile acids and dumping syndrome scores were higher in RYGB patients. Study 3: RYGB increased the intensity of fat/sweet taste solutions and reduced the reward value of fat/sweet stimuli. CONCLUSION: Pre-operative feeding may affect ingestive behaviour after RYGB. The mechanisms underlying the healthier food preferences after RYGB include the reduced reward value, and increased aversion to, high-calorie food and taste. Potential mediators are gut hormones, bile acids and altered gut nutrient sensing.Open Acces

Bariatric Surgery in Women with Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrine condition in premenopausal women and is a common cause of anovulatory subfertility. Although obesity does not form part of the diagnostic criteria, it affects a significant proportion of women with PCOS and is strongly implicated in the pathophysiology of the disease. Both PCOS and obesity are known to impact fertility in women; obesity also reduces the success of assisted reproductive technology (ART). With or without pharmacotherapy, lifestyle intervention remains the first-line treatment in women with PCOS and obesity. Bariatric surgery is still an experimental treatment in women with PCOS and subfertility. This review will present an overview of the pathophysiology of PCOS and obesity and the role of bariatric surgery. Although data are sparse regarding the impact of bariatric surgery on subfertility in women with PCOS and obesity, existing studies point to a beneficial role in treating metabolic and reproductive dysfunction. [Abstract copyright: Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.

Length of biliopancreatic limb in Roux-en-Y gastric bypass and its impact on post-operative outcomes in metabolic and obesity surgery-systematic review and meta-analysis

BACKGROUND: Roux-en-Y gastric bypass (RYGB) is a gold-standard procedure for treatment of obesity and associated comorbidities. No consensus on the optimal design of this operation has been achieved, with various lengths of bypassed small bowel limb lengths being used by bariatric surgeons. This aim of this systematic review and meta-analysis was to determine whether biliopancreatic limb (BPL) length in RYGB affects postoperative outcomes including superior reduction in weight, body mass index (BMI), and resolution of metabolic comorbidities associated with obesity. METHODS: A systematic search of the literature was conducted up until 1st June 2021. Meta-analysis of primary outcomes was performed utilising a random-effects model. Statistical significance was determined by p value  0.05). Even though results of four studies showed superior total body weight loss in the long BPL cohorts at 24 months post-operatively (pooled mean difference −6.92, 95% CI –12.37, −1.48, p = 0.01), this outcome was not observed at any other timepoint. CONCLUSION: Based on the outcomes of the present study, there is no definitive evidence to suggest that alteration of the BPL affects the quantity of weight loss or resolution of co-existent metabolic comorbidities associated with obesity

Impact of insulin sensitisation on metabolic and fertility outcomes in women with polycystic ovary syndrome and overweight or obesity - a systematic review, meta-analysis, and meta-regression

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in reproductive-age women. This systematic review, meta-analysis and meta-regression aims to compare the effect of insulin sensitiser pharmacotherapy on metabolic and reproductive outcomes in women with PCOS and overweight or obesity. We searched online databases MEDLINE via OVID, EMBASE, Clinicaltrials.gov and EudraCT for trials published from inception to 13th November 2023. Inclusion criteria were double-blind, randomised controlled trials in women diagnosed with PCOS, body mass index (BMI) ≥ 25 kg/m2, which reported metabolic or reproductive outcomes. The intervention was insulin sensitisation pharmacotherapy versus placebo or other agents. The primary outcomes were the changes from baseline BMI, fasting blood glucose and menstrual frequency. Nineteen studies were included in this review. Metformin had the most significant effect on the fasting plasma glucose and body mass index. Insulin sensitiser pharmacotherapy significantly reduced fasting plasma glucose, body mass index, fasting serum insulin, HOMA-IR, sex hormone binding globulin and total testosterone, but the effect size was small. There was a lack of menstrual frequency and live birth data. The results indicate a role for insulin sensitisers in improving the metabolic and, to a lesser degree, reproductive profile in these women. Further research should examine insulin sensitisers' effects on objective measures of fecundity

Bariatric-metabolic surgery for NHS patients with type 2 diabetes in the United Kingdom National Bariatric Surgery Registry

Aim: Bariatric-metabolic surgery is approved by the National Institute of Health and Care Excellence (NICE) for people with severe obesity and type 2 diabetes (T2DM) (including class 1 obesity after 2014). This study analysed baseline characteristics, disease severity and operations undertaken in people with obesity and T2DM undergoing bariatric-metabolic surgery in the UK National Health Service (NHS) compared to those without T2DM. Methods: Baseline characteristics, trends over time and operations undertaken were analysed for people undergoing primary bariatric-metabolic surgery in the NHS using the National Bariatric Surgical Registry (NBSR) for 11 years from 2009 to 2019. Clinical practice before and after the publication of the NICE guidance (2014) was examined. Multivariate logistic regression was used to determine associations with T2DM status and the procedure undertaken. Results: 14,948/51,715 (28.9%) participants had T2DM, with 10,626 (71.1%) on oral hypoglycaemics, 4322 (28.9%) on insulin/other injectables, and with T2DM diagnosed 10+ years before surgery in 3876 (25.9%). Participants with T2DM, compared to those without T2DM, were associated with older age (p &lt; 0.001), male sex (p &lt; 0.001), poorer functional status (p &lt; 0.001), dyslipidaemia (OR: 3.58 (CI: 3.39–3.79); p &lt; 0.001), hypertension (OR: 2.32 (2.19–2.45); p &lt; 0.001) and liver disease (OR: 1.73 (1.58–1.90); p &lt; 0.001), but no difference in body mass index was noted. Fewer people receiving bariatric-metabolic surgery after 2015 had T2DM (p &lt; 0.001), although a very small percentage increase of those with class I obesity and T2DM was noted. Gastric bypass was the commonest operation overall. T2DM status was associated with selection for gastric bypass compared to sleeve gastrectomy (p &lt; 0.001). Conclusion: NHS bariatric-metabolic surgery is used for people with T2DM much later in the disease process when it is less effective. National guidance on bariatric-metabolic surgery and data from multiple RCTs have had little impact on clinical practice.</p

Does Bypass of the Proximal Small Intestine Impact Food Intake, Preference, and Taste Function in Humans? An Experimental Medicine Study Using the Duodenal-Jejunal Bypass Liner

The duodenal-jejunal bypass liner (Endobarrier) is an endoscopic treatment for obesity and type 2 diabetes mellitus (T2DM). It creates exclusion of the proximal small intestine similar to that after Roux-en-Y Gastric Bypass (RYGB) surgery. The objective of this study was to employ a reductionist approach to determine whether bypass of the proximal intestine is the component conferring the effects of RYGB on food intake and sweet taste preference using the Endobarrier as a research tool. A nested mechanistic study within a large randomised controlled trial compared the impact of lifestyle modification with vs. without Endobarrier insertion in patients with obesity and T2DM. Forty-seven participants were randomised and assessed at several timepoints using direct and indirect assessments of food intake, food preference and taste function. Patients within the Endobarrier group lost numerically more weight compared to the control group. Using food diaries, our results demonstrated similar reductions of food intake in both groups. There were no significant differences in food preference and sensory, appetitive reward, or consummatory reward domain of sweet taste function between groups or changes within groups. In conclusion, the superior weight loss seen in patients with obesity and T2DM who underwent the Endobarrier insertion was not due to a reduction in energy intake or change in food preferences

Effects of obesity surgery on food preferences, taste and reward in animals and humans

BACKGROUND: After Roux-en-Y gastric bypass bariatric surgery (RYGB) patients and animal models show a decreased preference for sweet/fatty foods. However, there are significant discrepancies in the findings of animal and human studies, and the mechanisms are not understood. AIMS: To investigate: 1. The effect of a high-fat (HFD) vs. low-fat (LFD) pre-operative maintenance diet on the ingestive behaviour of rats after RYGB 2. The effects of RYGB vs. gastric banding (BAND) surgery on food hedonics and brain reward systems in humans 3. The effects of RYGB on taste in humans METHODS: Study 1: Rats were fed either LFD or HFD before RYGB or sham surgery. Ingestive behaviour was assessed after surgery using food preference tests. Study 2: Brain reward responses to food were investigated using functional magnetic resonance imaging (fMRI), eating behaviour and metabolic phenotyping in body mass index (BMI) matched un-operated controls and patients after RYGB and BAND surgery. Study 3: The intensity and reward of sweet, fat and fat/sweet taste stimuli were assessed in patients undergoing RYGB using behavioural techniques. RESULTS: Study 1: Pre-operative maintenance diets with different fat contents, did not affect post-surgical weight loss or caloric intake. HFD-RYGB rats exhibited behaviour consistent with condition taste aversion to a familiar stimulus, compared to condition taste aversion to a novel stimulus in the LFD-RYGB rats. Study 2: Patients after RYGB had lower activation in brain reward systems to food and lower food hedonics than BAND patients and/or BMI-matched unoperated controls. Anorexigenic plasma gut hormones, plasma bile acids and dumping syndrome scores were higher in RYGB patients. Study 3: RYGB increased the intensity of fat/sweet taste solutions and reduced the reward value of fat/sweet stimuli. CONCLUSION: Pre-operative feeding may affect ingestive behaviour after RYGB. The mechanisms underlying the healthier food preferences after RYGB include the reduced reward value, and increased aversion to, high-calorie food and taste. Potential mediators are gut hormones, bile acids and altered gut nutrient sensing.Open Acces