Background: One anastomosis (mini) gastric bypass (OAGB) is believed to be more malabsorptive than Roux-en-Y gastric bypass. A number of patients undergoing this procedure suffer from severe protein–calorie malnutrition requiring revisional surgery. The purpose of this study was to find the magnitude of severe protein–calorie malnutrition requiring revisional surgery after OAGB and any potential relationship with biliopancreatic limb (BPL) length. Methods: A questionnaire-based survey was carried out on the surgeons performing OAGB. Data were further corroborated with the published scientific literature. Results: A total of 118 surgeons from thirty countries reported experience with 47,364 OAGB procedures. Overall, 0.37% (138/36,952) of patients needed revisional surgery for malnutrition. The highest percentage of 0.51% (120/23,277) was recorded with formulae using >200 cm of BPL for some patients, and lowest rate of 0% was seen with 150 cm BPL. These data were corroborated by published scientific literature, which has a record of 50 (0.56%) patients needing surgical revision for severe malnutrition after OAGB. Conclusions: A very small number of OAGB patients need surgical correction for severe protein–calorie malnutrition. Highest rates of 0.6% were seen in the hands of surgeons using BPL length of >250 cm for some of their patients, and the lowest rate of 0% was seen with BPL of 150 cm. Future studies are needed to examine the efficacy of a standardised BPL length of 150 cm with OAGB.

One Anastomosis/Mini Gastric Bypass (OAGB-MGB) is rapidly gaining popularity and is now the third common bariatric procedure performed in the world. The aim of this review is to look at the role of this operation as a revisional bariatric surgery (RBS). Literature review was performed following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) and the AMSTAR (Assessing the methodological quality of systematic reviews) guidelines. Total 17 studies were eligible. This review reports cumulative results of 1075 revisional OAGB-MGB procedures. Primary procedures included gastric banding (LAGB), Sleeve gastrectomy (SG), vertical banded gastroplasty (VBG) and gastric plication. The mean age was 43.1 years and female to male ratio was 3.04: 1. The body mass index (BMI) at primary procedure was 47.05 kg/m². The mean BMI at revisional surgery was 41.6 kg/m² (range 28-70.8). The mean time between the primary and the secondary operation was 46.5 months (3-264). The mean follow-up was 2.44 years (6-60 months). The mean operative time was 119.3 min. The mean length of hospital stay was 4.01 days (2-28). The median limb length was 200 cm (range 150-250 cm). Leak rate was 1.54%. Marginal ulcer rate was 2.44%. Anemia rate was 1.9%. Mortality was 0.3%. The excess weight loss (%EWL) at 1 year and 2 years was 65.2% and 68.5% respectively. We conclude that there is evidence to consider OAGB-MGB as a safe and effective choice for RBS. Randomised studies with long term follow-up are suggested for the future.