LETTER TO THE EDITOR Biliopancreatic Limb Lengths Affects Weight Loss in Roux-en-Y Gastric Bypass: Are We Close to the Truth? Ashish Dey 1 & Tarun Mittal 1 & Anmol Ahuja 1 & Vinod K. Malik 1 & Parmeshwar Bambrule 1 Received: 27 September 2020 /Revised: 1 October 2020 /Accepted: 6 October 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020 Dear Editor, This is in context to the randomized controlled trial by Jamie Ruizz et al., published in Obesity Surgery in 2019 [1]. It brings forth the idea that limb lengths in RYGB do not impact either the weight loss or the comorbidity resolution in RYGB, even in long term. Traditional teaching in bariatric surgery suggests three im- portant factors governing weight loss in Roux-en-Y gastric bypass (RYGB): (1) gastric pouch size, (2) gastrojejunal anas- tomosis size, and (3) biliopancreatic (BP) limb length, the last one having been generally accepted as the most important criteria affecting weight loss. The first 2 factors, gastric pouch size and gastrojejunal (GJ) anastomosis size, are limited by incidence of marginal ulcers on one side if too large and anas- tomotic stenosis on the other, the long-term weight loss, how- ever, being same in almost all studies. However, as far as BP limb lengths are concerned, results are far from conclusive. This is understandable because RCTs, systematic reviews, and meta-analysis focusing on these factors are not easy to perform in heterogenous groups of patients with a lot of con- founding bias, which brings us to a very pertinent question: What actually works towards weight loss? BP limb lengths in most studies are being correlated with weight loss, comorbidity resolution (most importantly diabe- tes resolution/control), and third being complications. Protein malnutrition due to malabsorption and resultant metabolic dis- orders appears to be the most important reasons in the long term to tailor limb lengths. BP limbs have been studied from 50 up to 250 cm. For obvious reasons of severe protein mal- nutrition, BP limb lengths longer than 250 cm have not been studied. Also the concept then changes from “long limb” RYGB to “distal” RYGB, where the remnant common chan- nel starts getting measured. This is where all similarities cease to exist and diversity in results starts appearing. There is one school of thought that BP limbs do not affect weight loss at all. In a series of recent RCTs that compared BP limb lengths, the results showed that “long limb” RYGB as compared with “standard” RYGB achieved similar results in percentage of total weight loss even in the long term [1, 2]. Even in separate cohorts of superobese people, standard and 250 cm long biliopancreatic limb did not show any difference in weight loss [3]. Another group of studies claims significant correlation of weight loss with BP limb lengths. In these studies, patients with longer BP limb lengths showed significantly higher %EWL in comparison with the patients with shorter BPL in the long term. These outcomes seem to hold true even in the concept of revisional surgeries, where increasing the BP limb lengths re- sults in greater weight loss and shows significant effect on resolution in diabetes in those select group of patients with weight regain and recurrence of diabetes [4, 5]. Systematic reviews in a select class of Superobese patients also showed, albeit considering considerable heterogenicity in all groups, that tailoring of a longer roux limb (alimentary limb) is beneficial even in the long term. The reason for superior weight loss and diabetes resolution in longer limbs have been credited to release of enterohormones in response to a food load in the distal small bowel. RYGB with a longer BP limb appeared to improve glycemic control and better remission in diabetics and also reduce diabetes relapse rates over time. Although ideal bowel * Ashish Dey ashishdey_78@rediffmail.com Tarun Mittal tarunmittalmas@gmail.com Anmol Ahuja dr.anmol14@gmail.com Vinod K. Malik vinod.k.malik@gmail.com Parmeshwar Bambrule pbbambrule@gmail.com 1 Department of General and Laparoscopic Surgery, Sir Ganga Ram Hospital, Old Rajinder Nagar, New Delhi 110060, India Obesity Surgery https://doi.org/10.1007/s11695-020-05033-x