Background/Objectives: The percentage of the world’s population with Class II obesity (body mass index (BMI) ≥ 35) and above is increasing annually. Bariatric (elective weight-loss) surgery is performed for less than one percent of eligible patients. A recent Delphi was unable to reach a consensus recommendation for or against mandated weight loss targets prior to bariatric surgery. This systematic review, performed according to the PRISMA 2020 guidelines, looks at the literature to determine whether there is evidence that pre-operative weight loss affects long-term (≥5 years) outcomes of bariatric surgery (weight loss, co-morbidity resolution). Methods: MEDLINE, EMBASE, CABI Digital Library, and Cochrane Central Register of Controlled Trials (Central) were searched from 1 January 2000 to 1 March 2025. Twenty-one full papers were then assessed, and only three papers met the eligibility criteria for inclusion in this review. Results: 1072 patients were included (age range 26–73 years, sleeve: bypass 60.3%:49.7%, F:M 70.2%:29.8%). The studies differed in their pre-operative preparation and selection criteria for surgery: one paper used an intensive pre-operative information course and mandated 5% weight loss. This study reported a significant association between pre-operative weight loss and long-term outcomes. Two papers had no mandated pre-operative weight-loss target and found there was no association between pre-operative weight loss and long-term outcomes. Conclusions: There is limited and conflicting evidence that pre-operative weight loss percentage affects long-term outcomes of bariatric surgery. Further research looking at five-, ten-, and twenty-year outcomes for bariatric patients is required, particularly randomised controlled trials or tier one evidence.

Background/Objectives: Obesity is extremely common among patients with end stage renal disease (ESRD) due to shared metabolic risk factors. Renal transplantation is the gold standard treatment for ESRD, however obesity is a major barrier due to increased anaesthetic risks, surgical complications and poorer graft outcomes. The aim of this study was to assess ESRD patients referred for metabolic bariatric surgery (MBS) in Scotland. Methods: Data from all adult patients with ESRD who were referred for MBS in Scotland from January 2014 to August 2025 were obtained retrospectively. Categorical data are presented as number and percentage; non-parametric continuous data are presented as median and inter-quartile range. A focused review of comparable published cohorts was performed for context. Results: A total of 9 patients with ESRD were referred for MBS over the study period; of these, 5 patients went on to have MBS. Of the patients who underwent MBS, the median age at referral was 47 years, 3 of 5 were female and the median starting weight and body mass index (BMI) were 131 kg and 49 kg/m² respectively. Four patients underwent laparoscopic sleeve gastrectomy, and 1 patient underwent one-anastomosis gastric bypass. The median length of hospital stay was 2 days. The median total percentage weight loss was 33.5% (range 27.7% to 48.1%). Four of the five patients were able to be activated on the transplant waiting list after successfully achieving their target weight after a median of 8.4 months. Of the 4 listed patients, 3 were transplanted with no post-operative complications, and 1 remains active on the waiting list. Across seven comparable cohorts (19 to 198 operated patients), all single- or two-centre, ours had the only national coverage. Listing and transplantation outcomes (4 of 5 listed, 3 of 5 transplanted) were broadly consistent with the range reported in these cohorts, although the small sample precludes formal comparison. Conclusions: In this small case series and review, MBS appeared safe and feasible in a highly selected group of patients with obesity and ESRD. MBS facilitates access to renal transplant but is under-utilised in Scotland. We plan to formalise a national treatment pathway to streamline access to bariatric services for patients with ESRD and enable more patients to undergo renal transplantation.

Obesity is associated with breast cancer risk, and metabolic bariatric surgery (MBS) may reduce obesity-related cancer incidence. Prior reviews suggest lower breast cancer incidence after MBS, but uncertainty remains across design, menopausal status, procedure type, and confounding control. We conducted a PROSPERO-registered systematic review (CRD420261384078), meta-analysis, and network meta-analysis according to PRISMA. PubMed, Embase/MEDLINE, and Scopus were searched for comparative studies of breast cancer incidence after MBS versus control. Risk of bias was assessed using ROBINS-I and certainty using GRADE. Seventeen studies including 343,531 surgical patients and 1,587,413 controls were included. MBS was associated with lower breast cancer incidence in the primary hazard-ratio analysis (HR 0.75, 95% CI 0.70–0.81; I² = 0%) and women-only cohorts (HR 0.74, 95% CI 0.67–0.81). Propensity-score-matched analyses showed a larger but heterogeneous association (RR 0.56, 95% CI 0.31–0.99; I² = 91%). Premenopausal estimates favoured MBS (HR 0.74, 95% CI 0.60–0.91), whereas postmenopausal estimates were not significant (HR 0.73, 95% CI 0.50–1.07). Network estimates favoured sleeve gastrectomy and Roux-en-Y gastric bypass versus control, but no procedure was superior. Certainty ranged very low-to-moderate overall. MBS may be associated with lower breast cancer incidence, but evidence remains observational; future work must clarify causality, patient selection, and procedure effects.