Biliopancreatic diversion for severe obesity: long-term weight maintenance and occurrence of nutritional complications are two facets of the same coin.

BACKGROUND: Despite the widespread clinical use of hypoabsorptive metabolic bariatric surgery, very long-term outcomes are still lacking. The aim of the study was to assess the long-term safety and efficacy of biliopancreatic diversion at 30 years in patients with class 3 obesity (BMI over 40 kg/m2). METHODS: This retrospective single-centre study used data from a prospectively collected database on a sample of consecutive patients submitted to biliopancreatic diversion with a minimum follow-up of 30 years. Outcomes assessed included overall survival, long-term weight loss and weight maintenance, remission of obesity-related co-morbidities, and short- and long-term surgical and/or nutritional or metabolic complications. RESULTS: Among 199 consecutive patients (136 female, 63 male) who had surgery between November 1992 and April 1994, the mean age at operation was 38 (range 14-69) years and mean preoperative BMI was 48.7 (32.0-74.3) kg/m2. At baseline, 91 of 199 patients (45.7%) had type 2 diabetes. At 20 and 30 years, 122 (61%) and 38 (19%) of the 199 patients respectively were available for follow-up. At 30 years, the overall mortality rate was 12% (23 of 199). Surgical complications were concentrated in the short-term follow-up, whereas nutritional or metabolic complications increased progressively over time. A nutritional complication was diagnosed in 73 of 122 patients (60%) at 20 years and 28 of 38 (74%) at 30 years. Weight loss and glycaemic control were maintained throughout the follow-up; mean % total weight loss was 32.8 (range 14.1-50.0) at 1 year and 37.7 (range 16.7-64.8) at 30 years. One patient presented with recurrence of type 2 diabetes at 20 and 30 years; there were no patients with new-onset type 2 diabetes. CONCLUSION: Biliopancreatic diversion leads to good and sustained weight maintenance up to 30 years with low perioperative risk, but at the cost of a high long-term prevalence of nutritional complications.

Long-term comparative study on open versus laparoscopic biliopancreatic diversion.

BACKGROUND: To date, bariatric surgery has been proposed as the most effective treatment to resolve morbid obesity, a multifactorial chronic disease with an epidemic and increasing tendency. The purpose of this study was to determinate the impact of the laparoscopy on weight loss parameters in morbid obese patients who underwent surgery according to Scopinaro's biliopancreatic diversion (BPD) and evaluate early and late complications related to the open and laparoscopic approach of this technique. MATERIALS AND METHODS: This is a longitudinal retrospective study in consecutive patients undergoing BPD due to morbid obesity between 1999 and 2015. From 2006 the laparoscopic technique was introduced in our group for obesity surgery. In both approaches, open and laparoscopic surgery, the procedure performed consists of a proximal gastric section with a long Roux-en-Y reconstruction. The following variables were assessed in the two groups: intervention duration (min), estimated blood loss (mL), conversions to open approach (%), preoperative stay, postoperative and global stay (days). Complications were divided into early and late postoperative complications. The early surgical complications were catalogued according to the Clavien-Dindo classification. RESULTS: Two hundred seventy-seven patients were consecutively enrolled and divided in two groups: open BPD and laparoscopic BPD. There were no significant differences in the comparison of the two groups and the mean age was 43.9 years (19-60) with a mean BMI of 52.5 kg/m2. A statistically significant reduction was observed in favor of the laparoscopic group with respect to the reduction in hospital stay and in the incidence of incisional hernia as a late complication. No statistically significant difference were found with respect to early postoperative complications. CONCLUSIONS: Laparoscopic BPD is a safe technique that allows a shorter hospital stay compared to open surgery and that allows a drastic reduction in the incidence of incisional hernias.

In obesity with T2DM, biliopancreatic diversion increased T2DM remission vs. medical and lifestyle therapy at 10 y.

SOURCE CITATION: Mingrone G, Panunzi S, De Gaetano A, et al. Metabolic surgery versus conventional medical therapy in patients with type 2 diabetes: 10-year follow-up of an open-label, single-centre, randomised controlled trial. Lancet. 2021;397:293-304. 33485454.

Late complications of biliopancreatic diversion in an older patient: a case report.

BACKGROUND: In the mid-seventies, biliopancreatic diversion became popular as weight-loss surgery procedure. This bariatric procedure combines distal gastric resection and intestinal malabsorption, leading to greater weight loss and improvement of co-morbidities than other bariatric procedures. Nowadays, biliopancreatic diversion has become obsolete due to the high risk of nutritional complications. However, current patients with biliopancreatic diversions are aging. Consequently, geriatricians and general practitioners will encounter them more often and will be faced with the consequences of late complications. CASE PRESENTATION: A 74-year old female presented with weakness, recurrent falls, confusion, episodes of irresponsiveness, anorexia and weight loss. Her medical history included osteoporosis, herpes encephalitis 8 years prior and a biliopancreatic diversion (Scopinaro surgery) at age 52. Cerebral imaging showed herpes sequelae without major atrophy. Delirium was diagnosed with underlying nutritional deficiencies. Biochemical screening indicated vitamin A deficiency, vitamin E deficiency, zinc deficiency and severe hypoalbuminemia. While thiamin level and fasting blood glucose were normal. However, postprandial hyperinsulinemic hypoglycemia was observed with concomitant signs of confusion and blurred consciousness. After initiating parenteral nutrition with additional micronutrient supplementation, a marked improvement was observed in cognitive and physical functioning. CONCLUSIONS: Long-term effects of biliopancreatic diversion remain relatively underreported in older patients. However, the anatomical and physiological changes of the gastrointestinal tract can contribute to the development of metabolic and nutritional complications that may culminate in cognitive impairment, functional decline and delirium. Therefore, it is warranted to evaluate the presence of metabolic disturbances and nutritional complications in older patients after biliopancreatic diversion.

Long-Term Follow-Up Study of Liver-Related Outcome After Bilio-Pancreatic Diversion in Patients with Initial, Significant Liver Damage.

BACKGROUND: Obesity is associated with NAFLD, and bariatric surgery has significant impact on this liver disease, with reported improvement in hepatic fibrosis. AIMS: To investigate the effects of bariatric surgery on long-term liver disease-related outcome in obese patients with nonalcoholic fatty liver disease (NAFLD) and significant liver damage. METHODS: This study included 56 NAFLD patients who underwent bilio-pancreatic diversion for morbid obesity and who had significant fibrosis at intraoperative liver biopsy. Data were analyzed at 1, 3, and 5 years of follow-up, and at the latest available visit in patients who had longer follow-up. We assessed the incidence of clinically relevant liver events (ascites, hepatic encephalopathy, portal hypertension-related bleeding, and jaundice) as well as modifications of a validated biochemical index such as the NAFLD score. RESULTS: During a median follow-up of 78 months, median weight decreased from 119 to 78 kg (P < 0.0001), and median body mass index decreased from 45.2 to 29.0 kg/m2 (P < 0.0001). None of the patients developed clinical complications of liver disease, and none died due to liver-related causes. Median NAFLD score significantly decreased (P = 0.0005) during follow-up from - 0.929 (- 1.543 to - 0.561) to - 1.609 (- 2.056 to - 1.102). The NAFLD score category was unchanged in 32 patients (57%), improved in 18 (32%), and worsened in 6 (11%). CONCLUSIONS: Patients with NAFLD and proven histological liver damage at surgery do not develop complications of liver disease in long term after bilio-pancreatic diversion. Moreover, noninvasive parameters of liver damage improve. Thus, preexisting liver damage does not seem to be a contraindication to bilio-pancreatic diversion.

Safety of supramesocolic surgery in patients with portal cavernoma without portal vein decompression. Large single centre experience.

BACKGROUND: Supra-mesocolic surgery (SMS) is complicated in patients with portal vein cavernoma (PC) and portal decompression is recommended. The aim of this study was to report a large single centre of SMS in patients with PC without portal decompression. METHODS: Between 2006 and 2013, all patients who met inclusion criteria were analyzed retrospectively. The primary endpoint was the feasibility rate, surgical and postoperative outcome. The secondary endpoints were the long-term outcome of patients who underwent biliary bypass for cholangitis. Risk factors for complications were studied. RESULTS: Thirty patients underwent 51 procedures. Pancreatitis was the main etiology of PC (19/30) and biliary obstruction was mainly related to the underlying disease and not to portal cholangiopathy (12/14). All planned procedures were successfully completed. Fourteen patients underwent biliary bypass. Median blood loss (250 ml), transfusion (n = 7), mortality (n = 0), overall morbidity (n = 12) and the median hospital stay (10 days). Good long-term control of cholangitis was achieved in the 9 patients alive with available follow-up. Significant risk factors for complications were a previous abdominal wall scar, previous intra-abdominal surgical field and liver fibrosis. CONCLUSION: SMS can be safely performed in patients with PC. In patients with risk factors for complications, portal decompression should be discussed.

[Incretin secretion and glucose metabolism in morbidly obese patients in the early and late periods after biliopancreatic diversion]. / Produktsiya inkretinov i obmen glyukozy u bol'nykh patologicheskim ozhireniem v rannem i otdalennom periode posle biliopankreaticheskogo shuntirovaniya.

AIM: To estimate the parameters of glucose metabolism and to assess the secretion of incretins in patients after biliopancreatic diversion (BPD) for morbid obesity (MO) in the early and late postoperative periods. SUBJECTS AND METHODS: The prospective part of the investigation included 22 patients with a body mass index of 35.8 to 68.4 kg/m2 and type 2 diabetes mellitus (T2DM). All the patients were examined before, 3 weeks and 3 months after BPD. The retrospective part covered 23 patients who were examined after BPD for MO; the postoperative period was 4.7 [2.3; 7.2] years. A control group consisted of 22 healthy, normal weight volunteers. A 75-g oral glucose tolerance test was carried out in all the groups to study the levels of glucose, immunoreactive insulin (IRI), glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP) and glucagon at 0, 30, 60, and 120 min. RESULTS: T2DM patients showed improvement in glucose metabolism just 3 weeks after BPD; following 3 months, they had normalized fasting blood glucose levels (5.6 [5.0; 6.0] mmol/l). During 3 months, glycated hemoglobin decreased from 7.5 [6.6; 8.5] to 5.7 [5.3; 5.9]%. In the early period following BPD, there was an increase in basal and postprandial GLP-1 levels associated with the peak IRI concentration. In the late period after BPD, the enhanced secretion of IRI and GLP-1 persisted, which was followed by a reduction in postprandial glucose levels in 4 of the 23 patients. CONCLUSION: T2DM remission does not depend on weight loss in the early period after BPD. In this period, the significant improvement of glucose metabolic parameters in patients with obesity and T2DM is associated with elevated GLP-1 levels. The altered incretin response is a stable effect of BPD and remains in its late period.

Totally robot-assisted biliary pancreatic diversion with duodenal switch: single dock technique and technical outcomes.

BACKGROUND: The biliopancreatic diversion with duodenal switch (BPD/DS) requires operating in three different abdominal quadrants. Previous techniques have used either two docks or a hybrid technique in which the robot is used only to suture the duodeno-ileal anastomosis, while the rest of the operation was performed laparoscopically. Recently, a modification in technique has allowed all operative steps to be completed robotically with a single dock. The operative technique and its technical results are described. METHODS: Operative technique is described. Baseline demographics, operative duration, length of stay, and adverse events (intraoperative, 30-days, and 1-year) of all primary totally robot BPD/DS cases are reported. RESULTS: From Nov. 2011 to Jan. 2014, 59 totally robotic BPD/DS operations were attempted. One was completed hybrid, and the rest were totally robotic. No robotic operation was converted to an open operation. Five trocars were placed, the small bowel was anchored to the anterior abdominal wall, and the robot was docked. Mean age was 44 ± 10 years with a mean preoperative BMI of 56 ± 9 kg/m(2). 69 % was female, and 71 % was Caucasian. Mean operative duration was 306 ± 80 min (60 min less than the hybrid technique). There were no mortality, leaks, venous thromboembolism, or bleeding requiring transfusion. Mean length of stay was 4.6 ± 4.3 days. Three patients were readmitted for nausea and vomiting. There was one superficial wound infection, and three patients needed reoperations in the first year, two for strictures, and one for debriding a suture abscess. CONCLUSIONS: All key technical components of the BPD/DS were performed with low morbidity and mortality with a single dock. Since the surgeon performed all key parts of the operation from the console, the need for experienced bedside assistance was minimized, resulting in shorter operative duration compared to the hybrid technique.

Biliopancreatic diversion: when a cure becomes a disease.

Phrynoderma is a type of follicular hyperkeratosis located primarily on the extensor surfaces of the extremities. It is most commonly seen in Africa and Southeast Asia, where it is correlated with malnutrition; however, it is rare in developed countries, where it is often the result of malabsorption secondary to pancreatic insufficiency, colectomy, chronic giardiasis, and bariatric surgery. Here, we report a case of a 51-year-old white male patient, who presented to our Institute with a 1-year history of diffuse, reddish-brown asymptomatic papules associated with follicular nodules. In association with cutaneous symptomatology, the patient complained of also having night blindness. The patient, 4 years before, underwent a bariatric surgical treatment, which included a biliopancreatic diversion. Histologic examination of skin biopsy revealed hyperkeratosis and irregular acanthosis of the epidermis in association with dilated follicular infundibulum filled with keratinous material, whereas the laboratory investigations showed hypovitaminosis A. Based on the patient's history and cutaneous biopsy, a final diagnosis of phrynoderma was made. The steady increase of obesity in developed countries results in a relative increase in bariatric surgery. This must involve a multidisciplinary team to manage nutrition deficiencies and prevent possibly important complications, as mentioned in this report.

Management of Malnutrition and Hepatic Impairment After Duodenal Switch.

BACKGROUND: Malnutrition and liver impairment after duodenal switch (DS) are possible and undesired complications, often conservatively treated. However, in specific cases, surgical revision may be necessary. This study aims to describe outcomes achieved by two bariatric surgery centers and address effectiveness and safety of revisional surgical procedures to resolve these complications. METHODS: A retrospective chart review was performed in two bariatric surgery centers from 2008 to 2022. Patients who required revisional surgery to treat malnutrition and/or liver impairment refractory to nutritional and total parenteral nutrition intervention (TPN) after duodenal switch were included. No comparisons were performed due to the descriptive nature of this study. RESULTS: Thirteen patients underwent revisional surgery, the mean age was 44.7, the 53.8% were females, and the mean preoperative BMI was 54.7 kg/m2; the mean time between DS and revisional procedure was 26.5 months, and 69.1% of patients were placed on TPN. One patient developed hepatic encephalopathy; one patient presented with ascites, pleural effusion, and renal insufficiency, undergoing reoperation after revisional procedure due to a perforated ileal loop. Mortality rate was 0%; all patients regained weight after the revisional procedure, and the mean total protein and albumin blood levels 12 months after surgery were 6.3 and 3.6 g/dl, respectively. CONCLUSIONS: While refractory malnutrition and/or liver failure are rare among patients post-DS, if underdiagnosed and untreated, this can lead to irreversible outcomes and death. All revisional procedures included in this study resulted in improvement of the nutritional status and reversal of liver impairment, with low complication rates.

Long-term effects of gastric bypass and duodenal switch on systemic exposure of atorvastatin.

BACKGROUND: A previous study of 22 patients undergoing either gastric bypass or duodenal switch showed increased systemic exposure of atorvastatin acid 3-8 weeks after surgery in the majority of patients. This study aimed to investigate the long-term effects on systemic exposure of atorvastatin acid in the same group of patients. METHODS: An 8-h pharmacokinetic investigation was performed a median of 27 months (range 21-45 months) after surgery. Systemic exposure was measured as the area under the plasma concentration versus the time curve from 0 to 8 h postdose (AUC0-8). Linear mixed models with AUC0-8 as the dependent variable were implemented to assess the effect of time, surgical procedure, and body mass index (BMI) as explanatory variables. RESULTS: The study enrolled 20 patients. The systemic exposure of atorvastatin acid changed significantly over time (p = 0.001), albeit there was substantial variation between subjects. The effect of time was attenuated but remained significant after adjustment for surgical procedure and BMI (p = 0.048). The initial AUC0-8 increase seen in the majority of patients 3-8 weeks after surgery was normalized long term, with 7 of the 12 gastric bypass patients and 6 of the 8 duodenal switch patients showing decreased AUC0-8 compared with preoperative values. CONCLUSIONS: The systemic exposure of atorvastatin showed a significant change over time after bariatric surgery, albeit with large inter- and intraindividual variations. The findings indicate that patients using atorvastatin or drugs with similar pharmacokinetic properties should be monitored closely for both therapeutic effects and adverse events the first years after gastric bypass and duodenal switch.

Totally changed, yet still the same: patients' lived experiences 5 years beyond bariatric surgery.

Bariatric surgery provides sustainable weight loss and increased quality of life for most, but not all patients. To increase the knowledge of this complex patient group and their needs during follow-up, we aimed to describe the essential meaning of bariatric surgery patients' long-term experiences by using a phenomenological lifeworld approach. Eight patients were interviewed between 5 and 7 years after bariatric surgery. Life after bariatric surgery was described as living with tension, ambivalence, and reinforced attention toward one's own body. The tension was related to embodied change and altered relations to the social world. The patients express an ongoing demand for control of health-related habits and practices, and to not lose control over the body again. Surgical weight loss and improved physical function do not necessarily mean changed health-related habits and practices in the long term. Experiencing weight regain is connected with emotional stress, shame, and self-contempt.

Optimal Small Bowel Limb Lengths of Roux-en-Y Gastric Bypass.

PURPOSE OF REVIEW: Gastric bypass and biliopancreatic diversion (BPD) have come full circle, from a loop configuration to a Roux-en-Y and finally back to a loop configuration as one anastomosis gastric bypass and single-anastomosis duodenal switch. Most surgeons performing Roux-en-Y gastric bypass (RYGB) do not measure the common channel (CC) length and most surgeons performing BPD do not measure the biliopancreatic limb length (BPL). RECENT FINDINGS: The small bowel length in humans is variable from as short as < 400 cm to as long as > 1000 cm. The combination of these two facts means that even if surgeons keep the limb lengths constant, surgeons will get variable limb length due to the variability of small bowel length in patients. Hence, outcomes of weight loss, resolution of medical problems, or developing nutritional deficiencies which are related to limb length are variable. In this article, we evaluate the published literature related to the effect of varying the Roux limb, BPL, CC, and total alimentary limb lengths on the outcomes of RYGB. We have focused on historical and current randomized controlled trials as well as systematic reviews and meta-analysis to outline the current literature and our interpretation of this literature.

Analysis of the Impact of the Learning Curve on the Safety Outcome of the Totally Robotic-Assisted Biliopancreatic Diversion with Duodenal Switch: a Single-Institution Observational Study.

INTRODUCTION: Totally robotic-assisted biliopancreatic diversion with duodenal switch (BPD/DS) learning curve has been described to be longer at approximately 50 cases, at which point operative time and complications rate decrease and tend to stabilize. This study aimed to form an analysis of the impact of the learning curve on the safety outcomes of the totally robotic-assisted BPD/DS. METHODS: A retrospective review of patients who underwent primary totally robotic-assisted BPD/DS by one of our certified bariatric and metabolic surgeon member of our institution was performed. The patients were classified into two groups, the learning stage group (first 50 cases) and the mastery stage group. Differences in operative time in minutes and postoperative outcomes were analyzed. RESULTS: Two hundred seventy-six patients were included. The operative time and the postoperative length of stay were significantly higher in the learning stage group (173.8 ± 35.8 min vs. 139.2 ± 30.2 min, p= 0.0001; 3.4 ± 1.4 days vs. 2.6 ± 0.9 days, p= 0.0002). The overall leakage rate was significantly higher in the learning stage group (8% vs. 0.4%, p= 0.0001). The global rate of complications for the learning stage group was 14%, and for the mastery stage group was 6.6% (p= 0.08). CONCLUSIONS: After the first 50 cases, the operative time, the length of stay, and the overall rate of complications decreased, being especially significant the decrease in the duodeno-ileal anastomosis leakage rate after reaching the learning curve.

Conversion of gastric sleeve to Roux-en-Y gastric bypass and biliopancreatic diversion/duodenal switch: safe and viable options.

BACKGROUND: Sleeve gastrectomy (SG) remains the most performed bariatric surgery. As numbers of SG increase, so do the numbers of patients requiring conversion for insufficient weight loss or weight regain. However, the literature has cited complication rates as high as 30% for reoperative bariatric surgery. OBJECTIVE: With the recent inclusion of conversion surgery variables in the Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program (MBSAQIP) database, we compared the safety and efficacy of SG conversion to Roux-en-Y gastric bypass (RYGB) versus biliopancreatic diversion and duodenal switch (BPD/DS). SETTING: MBSAQIP database. METHODS: Analysis of the 2020 MBSAQIP Participant Use Files revealed 6020 patients who underwent SG conversion to RYGB (5348) and BPD/DS (672). We examined 30-day outcomes including death, anastomotic leak, readmission, any complication, dehydration, and weight loss. RESULTS: There was no statistically significant difference in mortality (.12% versus 0%) or; complication rate (6.5% versus 5.1%) with SG conversion to RYGB or BPD/DS. There was a statistically significant difference in anastomotic leak (.5% versus 1.2%, P = .024). Interestingly, BPD/DS was less likely to require dehydration treatments (4.2% versus 2.2%, P = .009) and had fewer readmissions within 30 days (7.3% versus 5.4%, P = .043). CONCLUSIONS: Complication rates after conversion of SG to RYGB or BPD/DS may be significantly lower than previously reported and only slightly higher than after primary weight loss surgery. SG conversion to either RYGB or BPD/DS remain safe, viable options for patients who had insufficient weight loss or regain, and BPD/DS may be the better option in the appropriate patient.

Wernicke Encephalopathy After Bariatric Surgery: a Literature Review.

Wernicke encephalopathy (WE) is an acute neurological disorder classically characterized by ataxia, ophthalmoplegia, and altered mental status. This is caused by thiamine deficiency and is usually seen in malnourished populations. However, with the advent and rise of bariatric surgery in the last 50 years, WE has become an increasingly recognized and potentially deadly complication. Here, we review the populations at risk, clinical presentation, and the incidence of WE in the bariatric surgery population from 1985 to 2023. While the predominant procedure shifts throughout the years, the overall incidence of WE per 100,000 cases for the following procedures are sleeve gastrectomy (1.06), gastric band (1.16), RYGB (4.29), and biliopancreatic diversion with duodenal switch (8.92). Thus, early intervention and post-operative supplementation is recommended to prevent WE.

Short-Term (30-Day) Morbidity of Biliopancreatic Diversion Compared to Roux-en-Y Gastric Bypass as Revisional Procedures for Failed Vertical Banded Gastroplasty.

BACKGROUND: Silastic ring vertical gastroplasty (SRVG) and vertical banded gastroplasty (VBG) are associated with a high failure rate due to weight regain and complications at long-term follow-up. Consequently, surgical correction for such procedures is warranted. Controversy exists as to which surgical procedure is the ideal choice for such correction. Our aim is to compare short-term outcome of Roux-en-Y gastric bypass (RYGB) and biliopancreatic diversion (BPD) repair for failed VBG/SRVG bariatric procedures. METHODS: The medical records of patients with failed SRVG who underwent corrective procedures at our institute between 2004 and 2018 were retrospectively reviewed. Patients characteristics, surgical approaches, and intraoperative and post-operative complications were examined and compared. RESULTS: Sixty patients in total underwent a surgical corrective procedure for failed SRVG. Thirty-one patients underwent RYGB, and 29 patients underwent BPD. Major complications were seen more in the RYGB group (35% = 11) compared to the BPD (6.9% = 2). Even though anastomotic leak rates were not statistically significant (p = 0.053), an apparent tendency for such a complication was noted in the RYGB group. RYGB procedure had an increased 30-day complication rate (p = 0.055) compared to RYGB. Laparoscopic approach had statistically fewer complications than open approach. No mortality was observed in either group. CONCLUSION: Our study showed that BPD is a safe option with less complication rates than RYGB in the short-term period for surgical correction of failed VBG/SRVG procedures.

Bariatric surgery and bone disease: from clinical perspective to molecular insights.

The use of bariatric surgery for the treatment of morbid obesity has increased annually for the last decade. Although many studies have demonstrated the efficacy and durability of bariatric surgery for weight loss, there are limited data regarding long-term side effects of these procedures. Recently, there has been an increased focus on the impact of bariatric surgery on bone metabolism. Bariatric surgery utilizes one or more of three mechanisms of action resulting in sustained weight loss. These include restriction (gastric banding, vertical banded gastroplasty and sleeve gastrectomy), malabsorption surgery with or without associated restriction (Roux en Y gastric bypass, duodenal switch, biliopancreatic diversion and jejunoileal bypass) and changes in gut-derived hormones that control energy metabolism also referred to as neuro-hormonal control of energy metabolism (Roux en Y gastric bypass, duodenal switch, biliopancreatic diversion, jejunoileal bypass, surgical procedures as above and gastric sleeve). Weight reduction has been associated with increased bone resorption but the mechanisms behind this have not yet been fully elucidated. Each of the mechanisms of action of bariatric surgery (restriction, malabsorption, neuro-hormonal control of energy metabolism) may uniquely affect bone resorption. In this paper we will review the current state of knowledge regarding the relationship between bariatric surgery and bone metabolism with emphasis on possible mechanisms of action such as malnutrition, hormonal interactions and mechanical unloading of the skeleton. Further, we suggest a future research agenda.