Changes in Cognitive Function Following Bariatric Surgery: An Updated Systematic Review.

Since a previous systematic review published in 2016, there have been further studies investigating the association of changes in cognitive function following bariatric surgery. All studies since the original review that reported at least one element of cognitive function before and after bariatric surgery were eligible. A total of 137 additional studies were identified; 13 were included in addition to the 18 studies previously. Almost all studies reported improvements in at least one domain. Most revealed improvements were limited to a few domains and were not universal. Further findings investigated cognitive function improvement in relation to procedure choice, and mental health or quality of life post-surgery. Further high-powered studies are still necessary, but these findings support the impact of bariatric surgery on cognitive function in obesity.

Cognitive functioning in adolescents with severe obesity undergoing bariatric surgery or intensive non-surgical treatment in Sweden (AMOS2): a multicentre, open-label, randomised controlled trial.

Background: Severe obesity during childhood is associated with cognitive deficits. Studies in adults have suggested improvements in executive functioning and memory after bariatric surgery. Our aim was to explore changes in cognitive function in adolescents over two years after bariatric surgery or intensive non-surgical treatment. Methods: The Adolescent Morbid Obesity Surgery 2 (AMOS2) is a multicentre, open-label, randomised controlled trial in which adolescents (aged 13-16 years) with severe obesity (defined as body mass index (BMI) ≥35 kg/m2) at three specialised obesity centres in Sweden, were randomly assigned to receive bariatric surgery or intensive non-surgical treatment. Herein we report the results of the prespecified exploratory endpoint of change in cognitive functioning. Inclusion in AMOS2 required Tanner pubertal stage ≥3, previous participation in lifestyle obesity treatment for at least one year, and passed assessment form a paediatrician and a paediatric psychologist. Adolescents with severe intellectual disability or other severe, pervasive developmental disorder were excluded. Participants underwent baseline assessment of general intellectual ability, executive functioning, and memory before randomisation. Tests were administrated by clinical psychologists and repeated at one- and two-year follow-up timepoints. Differences in means between groups during follow-up are provided with confidence intervals. The trial is registered at ClinicalTrials.gov, NCT02378259. Findings: Between October 28 2015 and June 7 2017, 46 adolescents (74% girls), with a mean age of 15.8 (±0.92) years and a mean BMI of 42.8 (±5.4) kg/m2, were included and randomised (23 to bariatric surgery and 23 to intensive non-surgical treatment). At baseline 23/46 (50%) of the adolescents had general intellectual functioning classified as borderline or below. For 15/18 (83%) aspects of cognitive functioning, no significant differences in change over two years were identified between groups; Immediate (average difference during follow-up 1.0 [95% CI: -2.6 to 4.6]) and Delayed (0.5 [95% CI: -0.6 to 1.6]) Verbal Recall, Category Fluency (1.1 [95% CI: -1.6 to 3.8]) and Switching (1.5 [95% CI: -0.0 to 2.9]), Number (-6.0 [95% CI: -12.3 to 0.3]) and Letter (0.1 [95% CI: -5.2 to 5.3]) Sequencing, Number-Letter Switching (-10.3 [95% CI: -26.4 to 5.8]), Motor Speed (-8.3 [95% CI: -17.5 to 0.9]), Colour Naming (-1.9 [95% CI: -4.2 to 0.3]), Inhibition (-3.6 [95% CI: -9.6 to 2.5]), Inhibition Switching (-6.7 [95% CI: -15.3 to 1.9]), Mazes (-0.5 [95% CI: -4.9 to 3.9]), Digit Span Forward (0.1 [95% CI: -0.6 to 0.9 ]) and Backward (0.6 [95% CI: -0.4 to 1.6 ]), and Estimated IQ (0.4 [95% CI: -3.9 to 4.8]; all p > 0.05). Three sub-tests assessing fundamental cognitive skills improved more over two years in operated adolescents than in intensive non-surgical treatment; Letter Fluency (average difference during follow-up 3.8 [95% CI: 0.1-7.5]; p = 0.046), Visual Scanning (-6.5 [95% CI: -11.6 to -1.5]; p = 0.011), and Word Reading (-1.9 [95% CI: -3.3 to -0.4]; p = 0.011). Interpretation: In contrast to non-randomised studies in adults, we could not demonstrate an association of bariatric surgery and its accompanying significant weight loss with overall greater improvement in executive functions and memory in adolescents over two years compared with a non-surgical group without weight loss. However, lack of statistical power is a potential limitation. The clinical relevance of greater improvements in basic cognitive skills needs to be explored. Funding: Sweden's innovation agency (VINNOVA), Swedish Research Council, Joanna Cocozza foundation for paediatric research, The Skane University Hospital Psychology Research and Development Grant, Tore Nilsson's Foundation, SUS Foundations and Donations, and Mary von Sydow's Foundation.

Changes in adipose tissue distribution and relation to cardiometabolic risk factors after Roux-en-Y gastric bypass in adolescents.

BACKGROUND: Roux-en-Y gastric bypass (RYGB) among adolescents with obesity results in significant weight loss; however, depot-specific changes have been understudied. OBJECTIVE: We hypothesized that visceral adipose tissue (VAT) reduction in adolescents undergoing RYGB would be greater than other depots and associated with improvement in cardiometabolic risk factors. SETTING: Three specialized treatment centers in Sweden. METHODS: Fifty-nine adolescents underwent dual x-ray absorptiometry before surgery and at 1, 2, and 5 years after RYGB. Changes in body composition in multiple depots (total fat, lean body, gynoid fat, android fat, subcutaneous adipose tissue, and VAT) and cardiometabolic risk factors were assessed using multiple linear regression analysis and generalized estimating equations adjusting for age, sex, and baseline risk factor levels. Data are presented as percent change (95% CI) with regression models showing slopes and estimated P values. RESULTS: At 1 year post-RYGB, a significant reduction was observed across all body composition measures (P < .001) with the greatest reduction observed in VAT (-65.1% [-68.7, -61.8]). From year 1 to 5 years post-RYGB, a regain was observed in all depots except lean body mass (1.2% [.3, 2.7], P = .105). A sex-specific difference in overall trajectories was only observed in lean body mass with males consistently having higher mean levels. Change in VAT at 1 year correlated with change in triglycerides (slope: .21 mg/dL/kg, P = .034) and fasting plasma insulin (slope: 44 pmol/L/kg, P = .027). CONCLUSIONS: Adiposity measures all decreased after RYGB but poorly predicted change in cardiometabolic risk. Despite significant reductions at 1 year, a steady regain was observed out to 5 years, with values still well below baseline. Further research should consider control group comparison and extended follow-up.

Long-term Outcomes Following Adolescent Metabolic and Bariatric Surgery.

Severe obesity in adolescence negatively impacts upon health and wellbeing. Lifestyle modifications do not usually achieve a sufficient degree or durability of weight loss to mitigate the risk of medical complications. In recent years, metabolic and bariatric surgery (MBS), already a well-established treatment for adults with severe obesity, has emerged as an option in adolescents. Controlled studies in this age group have demonstrated substantial and sustained weight loss, improvements in associated health parameters, and a safety profile surpassing that observed in adult patients. This review aims to present published data on the results of MBS in adolescents with a focus on long-term outcomes. Indications for bariatric surgery and aspects of timing in the young person's life are also presented, along with safety considerations and factors influencing patient selection for surgery. We conclude, predominantly from short- to medium-term outcomes data, that MBS is a safe and valuable therapeutic option for adolescents with severe obesity. Considering the poor health and social wellbeing prognosis in this group, MBS appears to be underutilized. The need for continued research, multiprofessional specialist provision, coherent contemporary clinical guidelines, and routine long-term follow-up in adolescents undergoing MBS is highlighted.

Metabolic and bariatric surgery versus intensive non-surgical treatment for adolescents with severe obesity (AMOS2): a multicentre, randomised, controlled trial in Sweden.

BACKGROUND: Severe obesity in adolescents has a profound impact on current and future health. Metabolic and bariatric surgery (MBS) is increasingly used in adolescents internationally. However, to our knowledge, there are no randomised trials examining the currently most used surgical techniques. Our aim was to evaluate changes in BMI and secondary health and safety outcomes after MBS. METHODS: The Adolescent Morbid Obesity Surgery 2 (AMOS2) study is a randomised, open-label, multicentre trial done at three university hospitals in Sweden (located in Stockholm, Gothenburg, and Malmö). Adolescents aged 13-16 years with a BMI of at least 35 kg/m2, who had attended treatment for obesity for at least 1 year, passed assessments from a paediatric psychologist and a paediatrician, and had a Tanner pubertal stage of at least 3, were randomly assigned (1:1) to MBS or intensive non-surgical treatment. Exclusion criteria included monogenic or syndromic obesity, major psychiatric illness, and regular self-induced vomiting. Computerised randomisation was stratified for sex and recruitment site. Allocation was concealed for both staff and participants until the end of the inclusion day, and then all participants were unmasked to treatment intervention. One group underwent MBS (primarily gastric bypass), while the other group received intensive non-surgical treatment starting with 8 weeks of low-calorie diet. The primary outcome was 2-year change in BMI, analysed as intention-to-treat. The trial is registered at ClinicalTrials.gov, NCT02378259. FINDINGS: 500 people were assessed for eligibility between Aug 27, 2014, and June 7, 2017. 450 participants were excluded (397 did not meet inclusion criteria, 39 declined to participate, and 14 were excluded for various other reasons). Of the 50 remaining participants, 25 (19 females and six males) were randomly assigned to receive MBS and 25 (18 females and seven males) were assigned to intensive non-surgical treatment. Three participants (6%; one in the MBS group and two in the intensive non-surgical treatment group) did not participate in the 2-year follow-up, and in total 47 (94%) participants were assessed for the primary endpoint. Mean age of participants was 15·8 years (SD 0·9) and mean BMI at baseline was 42·6 kg/m2 (SD 5·2). After 2 years, BMI change was -12·6 kg/m2 (-35·9 kg; n=24) among adolescents undergoing MBS (Roux-en-Y gastric bypass [n=23], sleeve gastrectomy [n=2]) and -0·2 kg/m2 (0·4 kg; [n=23]) among participants in the intensive non-surgical treatment group (mean difference -12·4 kg/m2 [95% CI -15·5 to -9·3]; p<0·0001). Five (20%) patients in the intensive non-surgical group crossed over to MBS during the second year. Adverse events (n=4) after MBS were mild but included one cholecystectomy. Regarding safety outcomes, surgical patients had a reduction in bone mineral density, while controls were unchanged after 2 years (z-score change mean difference -0·9 [95% CI -1·2 to -0·6]). There were no significant differences between the groups in vitamin and mineral levels, gastrointestinal symptoms (except less reflux in the surgical group), or in mental health at the 2-year follow-up. INTERPRETATION: MBS is an effective and well tolerated treatment for adolescents with severe obesity resulting in substantial weight loss and improvements in several aspects of metabolic health and physical quality of life over 2 years, and should be considered in adolescents with severe obesity. FUNDING: Sweden's Innovation Agency, Swedish Research Council Health.

Metabolic and Bariatric Surgery in Adolescents: For Whom, When, and How?

Severe obesity in adolescence profoundly impacts health and social well-being. Lifestyle modifications are seldom successful in maintaining sufficient weight loss to mitigate the risk of complications. Metabolic and bariatric surgery (MBS) is a standard treatment for adult patients and has emerged as an option for adolescent patients. Several high-quality studies of adolescent MBS show substantial and sustained improvements both in weight and cardiometabolic parameters, as well as a safety profile similar to that seen in adult patients. Patients report improvements in health- and weight-related quality of life. Concerns around adolescent MBS can be attributed to a fear of side effects on growth and puberty, risk of nutritional deficiencies and osteoporosis, alcohol abuse, psychosocial vulnerability, and the ability to consent in the decision process. Guidelines give somewhat different recommendations, but the most comprehensive guidelines from the American Society for Metabolic and Bariatric Surgery recommend MBS for class III obesity or class II obesity with comorbidity. This mini-review aimed to pre-sent published data on MBS in adolescents. We discuss indications for MBS and the optimal timing in the young person's life, the choice of surgical method, and MBS in relation to the new anti-obesity medications. Based on data primarily from the USA and Sweden, we conclude that MBS is a valuable treatment option for adolescents with severe obesity that appears underutilized against the backdrop of the poor prognosis of severe obesity. We argue for continued research, development of guidelines, multi-professional teamwork, long-term follow-up, and centralization of adolescent MBS.

Metabolic and Bariatric Surgery in Adolescents.

PURPOSE OF REVIEW: The prevalence of obesity is increasing in all age groups. Following its success in adults, and with limited success using conservative therapies, metabolic and bariatric surgery (MBS) is increasingly being utilized in adolescents. This review highlights the current evidence and guidelines supporting its use. RECENT FINDINGS: Safety and efficacy mirror results seen in adults. The most recent evidence, as outcomes enter the long term, suggests that comorbidity resolution, including diabetes and hypertension, can even outperform that of adults. Mental health problems persist despite good weight loss. Overall, the positive early weight and comorbidity outcomes are well sustained into the long term. There is a growing need to prevent and treat adolescent obesity. Current evidence supports the use of MBS in adolescents. Ongoing and future studies will provide 10-year outcomes and assist in the refinement of multimodal pathways incorporating MBS for the treatment of severe childhood obesity.

Prevalence of insufficient weight loss 5 years after Roux-en-Y gastric bypass: metabolic consequences and prediction estimates: a prospective registry study.

OBJECTIVE: The study aimed to investigate the heterogeneity of weight loss 5 years after Roux-en-Y gastric bypass (RYGB) and the association with cardiometabolic health as well as to model prediction estimates of surgical treatment failure. DESIGN: Retrospective analysis of prospectively collected data from the Scandinavian Obesity Surgery Registry (SOReg). SETTING: 29 surgical units from the whole of Sweden contributed data. Inclusion was restricted to surgical units with a retention rate of >60% five years postsurgery. PARTICIPANTS: 10 633 patients were extracted from SOReg. In total 5936 participants were included in the final sample, 79.1% females. The mean age of participants before surgery was 39.4±9 years and mean body mass index (BMI) 42.9±5.1. 2322 were excluded (death before the 5-year follow-up (n=148), other types of surgery or reoperations (n=637), age at surgery <18 or >55 years (n=1329), presurgery BMI <35 kg/m2 (n=208)). In total, 2375 (29%) of eligible individuals were lost to the 5-year follow-up. MAIN OUTCOME: The occurrence of surgical treatment failure 5 years after surgery was based on the three previously published definitions: per cent excess BMI loss <50%, total weight loss <20% or BMI >35 where initial BMI was <50, or >40 where initial BMI was >50. In addition, we report the association between surgical treatment failure and biochemical markers of obesity-related comorbidity. We also developed predictive models to identify patients with a high risk of surgical treatment failure 5 years postsurgery. RESULTS: In total, 23.1% met at least one definition of surgical treatment failure at year 5 which was associated with (adjusted OR) with 95% CI): type 2 diabetes (T2D, OR 2.1; 95% CI 1.6 to 2.7), dyslipidaemia (OR 1.8; 95% CI 1.6 to 2.1) and hypertension (OR 1.9; 95% CI 1.6 to 2.2). Surgical treatment failure at 5 years was predicted by combined demographic and anthropometric measures from baseline, 1 and 2 years postsurgery (area under the curve=0.874). CONCLUSION: Laparoscopic RYGB leads to a marked and sustained weight loss with improvement of obesity-related comorbidity in most patients. However, 23% met at least one definition of surgical treatment failure, which was associated with a greater risk of relapse and a higher incidence of T2D, dyslipidaemia and hypertension 5 years after surgery. Poor initial weight loss and early weight regain are strong predictors of long-term treatment failure and may be used for early identification of patients who require additional weight loss support.

High estimated prevalence of bariatric surgery in young adults treated for pediatric obesity.

BACKGROUND: Despite the modest effects of behavioral treatment on obesity in adolescence, bariatric surgery is rarely performed. Obesity often persists from childhood to adulthood, but it is not known how many individuals proceed with bariatric surgery in young adulthood. OBJECTIVE: The aim of this study was to determine what proportion of individuals who received pediatric behavioral obesity treatment subsequently underwent bariatric surgery in early adulthood, and to identify predictors thereof. SETTING: National registries, Sweden. METHODS: In this prospective cohort study, the Swedish Childhood Obesity Treatment Register was linked to several national registers. RESULTS: The childhood obesity cohort included 6502 (45% females) with a median age at follow-up of 21.7 years (interquartile range [IQR] 5.2). Of these, 8.2% underwent bariatric surgery at a median age of 20.9 years (IQR 4.2). The estimated cumulative incidence of bariatric surgery at age 30 was 21.5%. Obesity-related co-morbidities were identified in 31.7% before bariatric surgery in the childhood obesity cohort. Predictors of bariatric surgery were female sex, high body mass index standard deviation score (BMI SDS) at the start and end of treatment, poor treatment response, as well as own or parental cardiometabolic disease. CONCLUSIONS: More than a fifth are estimated to undergo bariatric surgery in early adulthood, despite having received pediatric behavioral obesity treatment. Our results indicate that for many children, behavioral treatment is insufficient in reducing obesity and preventing obesity-related co-morbidity. Therefore, it is reasonable to assume that more effective treatment of adolescents with severe obesity, including more rigorous behavioral support and pharmacologic treatment, but also more frequent use of bariatric surgery, would benefit this group of patients.

Real-world use of workplace based assessments in surgical training: A UK nationwide cross-sectional exploration of trainee perspectives and consensus recommendations from the Association of Surgeons in Training.

BACKGROUND: Despite widespread uptake, the utility of Workplace Based Assessments (WBAs) is disputed and evidence underpinning their use is largely based upon their completion in ideal conditions, rather than the real-world setting. AIM: To ascertain the real-world usage of WBAs, as perceived by UK surgical trainees. MATERIALS AND METHODS: An anonymous online questionnaire conducted nationally via the Association of Surgeons in Training (ASiT). Evaluation of 906 completed trainee responses, across all surgical specialties and training levels, employed mixed methods to interpret quantitative and qualitative data. RESULTS: The sample permitted a 3.0% confidence level with acceptable internal consistency (Cronbach's alpha 0.755). Formative use was supported by 72.5% and summative use was rejected by almost as many (66.3%). WBA use was perceived to deviate markedly from that recommended by the Joint Committee on Surgical Training (JCST). Significant misuse was identified and elements perceived as inaccurate appear commonplace across the breadth of surgical specialties. Inaccurate completion was acknowledged by 89.6% of respondents and some trainers appear complicit, 147 individuals (16.2%) having reported this to trainers, 40.9% aware of 'unobserved sign-off', and 33.6% aware of 'password disclosure' by trainers. Furthermore, a majority of trainees felt the Annual Review of Competency Progression (ARCP) respected WBA quantity above quality (55.4%), and a third felt pressure to overstate the number completed (32.0%). Reasons for misuse appeared largely centred upon time restraints, lack of engagement and a will to achieve the required targets for career progression. 1.5 CONCLUSIONS: This study demonstrates that UK surgical trainees perceive that most trainees deviate from guidance in their use of WBAs. This is worrying in both the apparent frequency and nature of misuse and somewhat undermines existing evidence for their role in surgical training. Trainees perceive that required numbers of WBAs are too high, that training programmes fail to encourage their use as formative assessments, and that there is a lack of engagement by many trainees and trainers. We present consensus recommendations from ASiT for the improvement of WBA use in UK surgical training.

Laparoscopic roux-en-Y gastric bypass versus sleeve gastrectomy for teenagers with severe obesity - TEEN-BEST: study protocol of a multicenter randomized controlled trial.

BACKGROUND: Recent data support the use of bariatric surgery in adolescents with severe obesity following unsuccessful non-surgical treatments. Sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB) have demonstrated reasonably similar weight loss and reduction of obesity related comorbidities in randomized trials in adults. SG has internationally become the most commonly used procedure in adolescents, yet long-term outcome data are lacking. No randomized controlled trial comparing SG and RYGB has been performed in adolescents. OBJECTIVE: Determine whether SG is non-inferior to RYGB in terms of total body weight (TBW) loss in adolescents with severe obesity. METHODS: A multicenter randomized controlled non-inferiority trial. Two hundred sixty-four adolescents aged 13-17 (Tanner stage ≥IV) with severe obesity (corrected for age and sex) will be included. Adolescents agreeing to participate will be randomized to either RYGB or SG. The primary outcome is the proportion of participants achieving 20% TBW loss at 3 years postoperatively. Secondary outcomes include (i) change in body weight, body mass index (BMI) and BMI standard deviation score, (ii) incidence of adverse health events and need for additional surgical intervention, (iii) resolution of obesity-related comorbidities, (iv) prevalence of cardio metabolic risk factor measures, (v) bone health measures and incidence of bone fractures, (vi) quality of life including psychosocial health, patient satisfaction and educational attainment and (vii) body composition. Follow-up will extend into the long term. RESULTS: Not applicable. DISCUSSION: This study will, to our knowledge, be the first randomized controlled trial comparing SG and RYGB in adolescents with severe obesity. TRIAL REGISTRATION: The trial is registered at the Netherlands Trial Register on July 26th, 2018 - NTR7191 - https://www.trialregister.nl/trial/7191 (protocol version 5.0 - February 3th 2020).

5-year mental health and eating pattern outcomes following bariatric surgery in adolescents: a prospective cohort study.

BACKGROUND: Mental health problems are prevalent among adolescents with severe obesity, but long-term mental health outcomes after adolescent bariatric surgery are not well known. We aimed to assess mental health outcomes over 5 years of follow-up after Roux-en-Y gastric bypass surgery in adolescents who participated in the Adolescent Morbid Obesity Surgery (AMOS) study. METHODS: This was a non-randomised matched-control study in adolescents aged 13-18 years who had a BMI of 40 kg/m2 or higher, or 35 kg/m2 or higher in addition to obesity-related comorbidity; who had previously undergone failed comprehensive conservative treatment; and were of pubertal Tanner stage III or higher, with height growth velocity beyond peak. A contemporary control group, matched for BMI, age, and sex, who underwent conventional obesity treatment, was obtained from the Swedish Childhood Obesity Treatment Register. Data on dispensed psychiatric drugs and specialist treatment for mental disorders were retrieved from national registers with complete coverage. In the surgical group only, questionnaires were used to assess self-esteem (Rosenberg Self-Esteem [RSE] score), mood (Mood Adjective Checklist [MACL]), and eating patterns (Binge Eating Scale [BES] and Three-Factor Eating Questionnaire-R21 [TFEQ]). This study is registered with ClinicalTrials.gov (NCT00289705). FINDINGS: Between April 10, 2006, and May 20, 2009, 81 adolescents (53 [65%] female) underwent Roux-en-Y gastric bypass surgery, and 80 control participants received conventional treatment. The proportion of participants prescribed psychiatric drugs did not differ between groups in the years before study inclusion (pre-baseline; absolute risk difference 5% [95% CI -7 to 16], p=0·4263) or after intervention (10% [-6 to 24], p=0·2175). Treatment for mental and behavioural disorders did not differ between groups before baseline (2% [-10 to 14], p=0·7135); however, adolescents in the surgical group had more specialised psychiatric treatment in the 5 years after obesity treatment than did the control group (15% [1 to 28], p=0·0410). There were few patients who discontinued psychiatric treatment post-surgery (three [4%] receiving psychiatric drug treatment and six [7%] receiving specialised care for a mental disorder before surgery). In the surgical group, self-esteem (RSE score) was improved after 5 years (mixed model mean 21·6 [95% CI 19·9 to 23·4]) relative to baseline (18·9 [17·4 to 20·4], p=0·0059), but overall mood (MACL score) was not (2·8 [2·7 to 2·9] at 5 years vs 2·7 [2·6 to 2·8] at baseline, p=0·0737). Binge eating was improved at 5 years (9·3 [7·4 to 11·2]) relative to baseline (15·0 [13·5 to 16·5], p<0·0001). Relative changes in BMI were not associated with the presence or absence of binge eating at baseline. INTERPRETATION: Mental health problems persist in adolescents 5 years after bariatric surgery despite substantial weight loss. Although bariatric surgery can improve many aspects of health, alleviation of mental health problems should not be expected, and a multidisciplinary bariatric team should offer long-term mental health support after surgery. FUNDING: Swedish Research Council, VINNOVA, Västra Götalandsregionen, ALF VG-region, Region Stockholm, Swedish Child Diabetes Foundation, Swedish Heart and Lung Foundation, Tore Nilsson's Foundation, SUS Foundations and Donations, Capio Research Foundation, and Mary von Sydow's Foundation.

Closure of mesenteric defects during Roux-en-Y gastric bypass for obesity: A systematic review and meta-analysis protocol.

INTRODUCTION: Closure of mesenteric defects during laparoscopic Roux-en-Y gastric bypass surgery (RYGB) has not been fully established as standard operative practice. However, in recent years a body of evidence has emerged suggesting that non-closure of defects leads to increased rates of internal herniation and its potential consequences, including the need for reoperation, along with an associated morbidity and mortality risk. Within the emerging literature there has also been some evidence of a greater risk of 30-day complications in closure groups. This systematic review and meta-analysis aims to look at the existing evidence and provide guidance on whether closure of mesenteric defects should be standard operative practice. METHODS: The systematic review and meta-analysis has been registered a priori. A literature search will be performed interrogating the Medline and Embase databases via Ovid, and also the Cochrane Controlled Register of Trials (CENTRAL), to identify randomised and non-randomised studies reporting comparative outcomes following closure vs. non-closure of mesenteric defects during RYGB. The primary outcome will be reoperation for small bowel obstruction, and secondary outcomes will include internal herniation, jejuno-jejunal anastomosis narrowing or kinking, adhesions, complications (<30 days and >30 days after surgery), 30-day mortality, reoperation, and any other outcome deemed relevant and reported in more than one study.