Bariatric surgery summary 2022

This blog provides free general information for anyone who is seeking to understand more about the weight loss surgery, not intended as a medical consult. Please seek proper medical advice for individual assessment and management.


  • Weight loss surgery (sleeve, gastric bypass and other types of bypass) mainly works by a combination of restriction, rapid gastric/intestinal transit, changes in neuroendocrine signals/gut hormones, changes in gut microbiota and hypoabsorption or malabsorption (for the more aggressive bypass procedures).
  • The primary end point is durable/maintained long term weight loss. Secondary end points are resolution of medical co-morbidities (metabolic syndrome), improvement in health related quality of life and life expectancy by a significant reduction in premature cardiovascular mortality and cancers. Please reference the Swedish Obese Subject Study with over 20 years of follow up data.
  • Successful bariatric surgery should achieve >50% EWL and achieve optimal body composition changes at 12 months, to lose the fat mass but preserve lean muscle mass and bone mineral density.
  • However this is not possible for everyone. The results are often patient dependent (due to age, genetics, metabolism, medications, post menopausal hormonal change, etc) and also depends on the type of surgical procedure. Bear in mind obesity is a chronic relapsing medical condition, meaning eventually all patients have the propensity to regain weight.
  • Revisional malabsorptive surgery are becoming more common nowadays. It can be successful to achieve long term weight loss, resolution of medical co-morbidities and is a remedy for complications such as reflux but revision surgery often has much higher post op side effects, risk and complications both in terms of morbidity and mortality. 
  • Sometimes there are major issues with patient compliance to dietary/nutritional supplements, food/alcohol addiction, binge eating, grazing or other disordered eating behaviour or complicating psychological disorders 2 years or more after surgery, resulting in weight regain. 
  • Long term follow up may be difficult as well due to patient moving to a different geographical location, dropping private insurance cover, losing the close working relationship with their dietitian, psychologist, exercise physiologist, nurse, GP and surgeon over time.
  • Revisional bariatric surgery can be expected with the passage of time and may be unavoidable due to weight regain, return of medical co-morbidities or technical/medical complications of the index procedure, especially with the ever-increasing volume of primary bariatric operations being performed every week all around the world.

Special mention about female patients

  • Morbidly obese females account for up to 80% of patients undergoing bariatric surgery and approximately 43% are in the child bearing age group.
  • Future pregnancy may affect the choices of the primary bariatric surgery. Younger females may wish to reserve the bypass procedure in the future as a revision procedure.
  • Patients are advised to avoid getting pregnant in the first 12-18months after weight loss surgery or maybe finish their family first before undergoing any bariatric surgery. Please seek advice from your GP regarding contraceptive methods, such as intra-uterine device (Mirena).
  • Maternal medical/obstetric problems may include PCOS/subfertility, anovulation, irregular menses, miscarriage, gestational DM, HPT/pre-eclampsia, DVT, dystocia, preterm delivery, higher LUSCS rate, birth trauma, anaesthetic complication, PPH, infection. 
  • Paediatric problems may include a shorter gestation period, small for gestation age, stillbirth or neonatal death or conversely macrosomia, childhood obesity, DM or cardiovascular risk.

Summary laparoscopic sleeve gastrectomy (LSG)


  • The open sleeve gastrectomy was the initial part of the BPD-DS operation, was first performed around 1988. The LSG was first performed in 1999.
  • LSG is currently the most commonly performed bariatric surgery in the world (>53%) with good weight loss result, resolution of medical co-morbidities and have good safety profile.
  • Antral resection may achieve more weight loss, maintained weight loss longer overtime, have better resolution for T2DM, more satiety from delayed gastric emptying (but others reported more rapid gastric emptying and more rapid rise in GLP-1 hormones) but maybe also a slightly increased risk for reflux.
  • Adverse events include staple line leak, bleeding, gastric stenosis, volvulus, all of which are extremely serious.
  • The long term risk of reflux and Barrett’s oesophagus are around 28-47% and 8% respectively with at least 4% LSG needed to be converted to RYGBP for severe reflux oeosphagitis.
  • LSG may have 5 times more risk for reflux compare to RYGBP. Higher risks are found in females, in the older age group, higher BMI, using a smaller bougie size resulting in a narrower gastric pouch, staple firing closer to the pylorus and those with pre-existing reflux and hiatus hernia.
  • Despite LSG being regarded as a safe procedure, nutritional deficiencies may be pre-existing before surgery or may develop after surgery. Supplementation for iron, folate, vitamin D, Zinc, Magnesium and others will be necessary.


  • Compared to the RYGBP, LSG has lower remission rate for T2DM and hyperlipidaemia and has a higher risk for weight regain after 3 to 5 years. 
  • Some patients (28%) patients have inadequate weight loss (<50% EWL) and some patients have weight regain after successful result, which is termed “recidivism or relapse”. In the literature “failure” includes inadequate weight loss and relapse. 
  • A bigger remnant sleeve fundus has a higher risk for weight regain. Possibly up to 13% or more of the patients require resection of the fundus and/or conversion to another bariatric procedure.
  • Banded sleeve gastrectomy (with adjustable or non-adjustable ring) was introduced over 13 years but this is not recognized as a standard bariatric procedure. There may be better weight loss outcome after 3 to 5 years with the banded sleeve. 
    • Some studies showed that the banded sleeve is better for weight loss but other studies showed no advantage in terms of improvement of medical co-morbidities. 
    • The ring may increase the risk for dysphagia, regurgitation, vomiting or food intolerance and some need to be removed (maybe up to 7%). In the long term there may be a risk for migration, erosion and perforation.
  • A re-sleeve gastrectomy is generally not very successful with only about 28% mange to maintain sufficient long term weight loss result.
  • RYGBP is the revision procedure of choice for reflux and weight regain. Without reflux the option can include OAGB or SADI-S. In Australia the number of patients undergoing revision surgery to SADI-S is actually very low.

Summary laparoscopic one anastomosis gastric bypass (OAGB)


  • Currently OAGB is the 3rd most common bariatric/metabolic procedure performed in the world (since 2018).
  • OAGB is suitable for first time bariatric procedure or as a revisional surgery for non responders after a failed LSG.
  • First IFSO and now ASMBS had endorsed the OAGB but a lot of debate still exist in USA whether the OAGB should be recommended for majority or any of their patients.
  • OAGB was first performed/described in 2001 as the MGB. The surgery was modified and the name of the procedure was changed to OAGB in 2005.


Comparing OAGB with RYGBP

  • The YOmega trial in 2019 concluded that OAGB was not inferior to RYGBP regarding weight loss and metabolic improvements (control of DM) but have a higher incidence of diarrhoea, steatorrhoea and nutritional deficiencies (these trials performed a 200cm BP limb which may explain the higher rate of nutritional complications 7.7%). 
  • Another trial similarly showed OAGB has a higher risk for anaemia (44%), hypoalbuminaemia (32%) and hypocalcemia (19%) compared to the RYGBP risk for anaemia (17%), hypoalbuminaemia (15%) and hypocalcemia (8%) over 5 years.
  • Improved HbA1c control and better 5 years resolution rate for T2DM is seen with OAGB (70.5%), better than RYGBP (39%).
  • Meta-analysis (in 2019 and 2022) showed that there was better weight loss results and DM remission result for OAGB than RYGBP up to 5 years post op but no difference in remission of HPT and dyslipidaemia between the 2 surgeries. 
    • The incidence of for leaks, marginal ulcer, dumping and revision surgery were  similar between the 2 groups but there is a higher risk for internal hernia and small bowel obstruction in the RYGBP group as expected.
  • There are concerns with OAGB regarding bile reflux (up to 10% of cases), oesophageal and gastric cancers and malabsorption/malnutrition following a longer BP limb (>230-250cm). 
    • May have a long term risk of anaemia (up to 12-20%), low albumin (up to 8-60%) and low calcium (>20%) ?
  • New onset of reflux rate may be around 11% after 8 years and some patients need to have a revision to a RYGBP.
  • The internal hernia risk after OAGB has also been reported up to 2.8% of cases.

Patient selection

  • OAGB is a good option as a stand alone or 2 stage bariatric procedure for those with a BMI over 50, 60 or 70.
  • OAGB may be indicated for patients with T2DM, fatty liver disease, vegetarian, CRF (not on dialysis) and severe arthritis.
  • This is an appropriate revision surgery for insufficient weight loss or relapse (weight regain) after LSG.
  • Relative contraindication may include Helicobacter pylori resistant patients, those with severe reflux, Barrett’s oesophagus, gastric or duodenal ulcers ?
  • OAGB is probably not appropriate for weight regain after RYGBP.

Summary laparoscopic single anastomosis sleeve jejunal or ileal (SASJ and SASI)


  • This procedure combines the LSG with OAGB.
  • Single anastomosis sleeve ileal and sleeve jejunal procedures are the newer more experimental surgery in an attempt to achieve more weight loss and greater resolution of medical problems such as DM, HPT, hyperlipidaemia, fatty liver disease and OSA.
  • The disadvantage is that some patients may lose too much weight and this surgery may need to be reversed.


  • The Santoro procedure is a sleeve gastrectomy with transit bipartisan and have 2 anastomoses. The newer operations below are a variation of the Santoro but only have 1 anastomosis.
  • SASI is done with an anastomosis 1/3 of the length from the ileo-caecal junction. 
  • SASJ is done with an anastomosis 1/3 of the length from the ligament of Treitz. This has a shorter BP length than the SASI, thus may have less long term nutritional complications and a lower reversal rate.
  • SASI will have to be reversed for those with excessive weight loss and hypoalbuminaemia.


  • More information about the SASJ and SASI will be available in the next few years.

Summary laparoscopic Roux Y gastric bypass (RYGBP)


  • The Roux reconstruction was introduced in 1977 for bile reflux, with time this was adopted into bariatric surgery. Currently RYGBP is the second most common weight loss surgery in the world (38%).
  • RYGBP has been performed for over 40 years in the USA. The criticism of the RYGBP is that there is no standardization of the procedure in terms of the size/length of the proximal gastric pouch, the alimentary limb or BP limb length.
  • Despite variations in surgical technique some surgeons still regard RYGBP as the gold standard weight loss procedure, as an index or salvage procedure. 


  • It has been reported that patients lose up to 35% total body weight in the first 2 years after RYGBP with good resolution rate for T2DM (84%), HPT (68%) and hyperlipidaemia (97%). 
  • In the long term up to 30% patients will regain weight. The late weight regain after RYGBP may be due to gastric pouch and outlet dilatation resulting in less restriction.
  • RYGBP is technically harder to do and may have more complications than the LSG and OAGB.

Comparing RYGBP vs LSG

  • A systematic review and meta-analysis (in 2020) reported good results for LSG and RYGBP in terms of sustained weight loss and control of co-morbidities at 5 years. In the long term the RYGBP resulted in a greater percentage excess weight loss (65% vs 57%). However although this may be statistically significant it may not be clinically significant. 
  • There are also improved dyslipidaemia outcomes (68% vs 55%) and less reflux in the RYGBP group as expected. 
  • Both groups RYGBP vs LSG produced improvements in diabetes control (in 2/3 of the cases), control for HPT (86% vs 76%) and improvements in quality of life but there were no statistically significant differences between these 2 groups.
  • RYGBP is a great salvage procedure for reflux after LSG. It is also a good salvage operation after OAGB for intractable bile reflux, neuroglycopenia, malnutrition or technical complications such as afferent loop syndrome or gastro-gastric fistula/ulcer (by reducing the BP limb back to around 70cm and 150cm alimentary limb).

Summary laparoscopic single anastomosis duodenal ileal bypass with sleeve gastrectomy or stomach intestinal pylorus preserving surgery (SADI-S or SIPS)


  • This was initially described in 2007, which incorporate a LSG combined with a modified one anastomosis loop DS. SADIS-S is now recognized by IFSO as a bariatric/metabolic procedure but more research onto long term results and nutritional deficiencies and complications are needed.


  • Some have reported 80-100% EWL after SADI-S at 2-5 years, results depending on the length of the common channel.
  • A systemic review and meta-analysis (2022) for SADI-S when compared to RYGBP and OAGB showed better outcomes for total body weight loss and remission of T2DM. 
  • SADI-S has better weight loss than DS but the T2DM remission and correction for dyslipidaemia is better with DS. 

Patient selection

  • SADI-S are usually selected for patients with the most severe obesity that have the most metabolic dysfunction. 
  • It may be an option for revisional surgery after a failed LSG or RYGBP within the first year.
  • SADI-S has been reported to have more post op complications (up to 6%) and re-operation rate (up to 3%) compared to the LSG, OAGB and RYGBP. 
  • SADI-S has a better QOL than the BPD in terms of diarrhoea/steatorrhoea.
  • The main concern is the malabsorption complications and the need for revision surgery because of under nutrition and protein deficiency in the long term but the risk can be reduced when the common channel is increased to more than 250-300cm. Very strict follow up guidelines are needed after this operation.
  • More information about the SADI-S will be available in the next few years.

Summary for weight regain operations

Before proceeding to revision surgery, many other factors such as the dietary compliance, addiction to alcohol, relapse of bad eating habits, negative changes to lifestyle behaviours, psycho-social issues (eg. divorce, anxiety/depression), etc need to be addressed first.

After a sleeve gastrectomy there may be inadequate weight loss, weight regain, return of medical co-morbidities, reflux or other issues which require revision/conversion surgery. There may be up to 37% of patients who require revision surgery. For some patients this is deliberate/planned as part of a 2 stage procedure.

A re-sleeve gastrectomy is only beneficial for an enlarged remnant fundus (primary dilatation), retained enlarged antrum or (secondary) pouch dilatation for patients who have lost the restriction (? more than 250mls gastric sleeve volume). A re-LSG may result in reduction of 10 BMI points after 2 years.

RYGBP is a good revision surgery option for weight regain and acid or alkaline/bile reflux after LSG or OAGB. There may be a 14 BMI points reduction after 2 years. 

  • Complications may include leaks, anastomotic stricture (requiring gastroscopy/dilatation), marginal ulcers and/or long term nutritional deficiencies.

OAGB is a good revision surgery option for weight regain in patients without acid/alkaline reflux. This is probably the revision surgery of choice after a LSG with good weight loss result. There may be a 14 BMI points reduction after 2 years. 

  • Similarly complications may include leaks, anastomotic stricture (requiring gastroscopy/dilatation), alkaline/bile reflux, marginal ulcers or long term nutritional deficiencies.

SADI-S and DS has been described as well. DS has the best weight loss after a failed sleeve. 

  • However the more technically complex the operation, the higher the post op complications (for leaks, sepsis, fistula, bleeding, etc) and the higher risk for malabsorption/malnutrition.


Obes Surg 2002; 12 (5): 705-717. Buchwald H, Buchwald J. Evolution of operative procedures for the management of morbid obesity 1950-2000.

Obes Surg 2020; 30: 664-672. Sharples A, Mahawar K. Systematic review and meta-analysis of randomised controlled trials comparing long term outcomes of Roux-en-Y gastric bypass and sleeve gastrectomy.

Obes Surg 2021; 31 (4): 1411-1421. Haddad A, Bashir A, Fobi M, et al. The IFSO worldwide one anastomosis gastric bypass survery: technique and outcomes ?

Obes Surg 2022; 32: 2512-2524. Patient selection in one anastomosis/minigastric bypass an Expert Modified Delphi consensus.

Obes Surg 2019; 29: 2721-2730. Dimitrios M, Vasiliki S, Tasiopoulou, et al. One anastomosis gastric bypass versus Roux-en-Y gastric bypass for morbid obesity: an updated Meta-analysis.

Obes Surg 2022; 32: 1-9. Yichen L, Yijie G, Yulia J, et al. What is the efficacy of short length of biliopancreatic limb in one anastomosis gastric bypass? A systematic  review and meta analysis of short term results.

Lancet 2019; 393 (10178): 1299-1309. Robert M, Espalieu P, Pelascini E, et al. Efficacy and safety of one anastomosis gastric bypass versus Roux-en-Y gastric bypass for obesity (YOMEGA): a multicentre, randomised, open-label, non-inferiority trial.

Ann Surg 2005; 242 (1): 20-28. Lee W, Yu P, Wang W, et al. Laparoscopic Roux-en-Y versus mini-gastric bypass for the treatment of morbid obesity.

Surg Obes Relat Dis 2019; 15 (12): 2038-2044. Bhandari M, Nautiyal H, Kosta S, et al. Comparison of one anastomosis gastric bypass and Roux-en-Y gastric bypass for treatment of obesity; 15 year study.

Surg Obes Relat Dis 2021; S1550-7289 (21): 00186-6. Zerrweck C, Herrera A, Sepulveda E, et al. Long versus short biliopancreatic limb in Roux-en-Y gastric bypass: short term results of a randomised clinical trial.

Surg Obes 2022; 32: 2582-2590. Seyed H, Nader M, Pourya M, et al. Optimal length of biliopancreatic limb is single anastomosis sleeve gastrointestinal bypass for treatment of severe obesity: efficacy and concerns.

N Engl J Med 2004; 351 (26): 2683-93. Sjostrom L, Lindroos AK, Peltonen M, et al. Lifestyle, Dibetes and Cardiovascular Risk Factors 10 years after bariatric surgery.

J Intern Med 2013; 273: 219-234. Sjostrom L. Review of the key results from the Swedish Obese Subjects (SOS) trial – a prospective controlled intervention study of bariatric surgery. 

N Engl J Med 2020; 383: 1535-1543. Carlsson L, Sjoholm K, Jacobson P, et al. Life expectancy after bariatric surgery in the Swedish Obese Subject Study.

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Aust Prescr 2022; 45: 38-40. Proietto J. Medicines for long term obesity management


ASMBS             American Society for Metabolic and Bariatric Surgery

BMI                 Body mass index

BPD-DS            Biliopancreatic diversion with duodenal switch

CRF                  Chronic renal failure

DM                  Type 2 diabetes mellitus

DVT                 Deep venous thrombosis

EWL                 Excess weight loss

HPT                 Hypertension

IFSO                 International Federation for the Surgery of Obesity and Metabolic disorders

LUSCS              Lower uterine Caesarean section

MGB                Mini gastric bypass

OSA                 Obstructive sleep apnoea

PCOS               Polycystic ovarian syndrome

PPH                 Post partum haemorrhage

Medications for weight loss

Please visit the webpage above about information regarding medication used for weight loss. Especially information on the weight loss results, indications, contraindications and side effects of these medications.

Anti-obesity medications available in Australia in 2022 include:

  • Phentermine (Duromine)
  • Orlistat (Xenical)
  • Liraglutide (Saxendra)
  • Semaglutide (Ozempic)
  • Bupropion and Naltrexone (Contrave)
  • Topiramate (Topomax)

Other GLP-1 injections available for T2DM and weight loss include:

  • Dulaglutide (Trulicity)
  • Exanatide (Byetta, Bydureon)
  • Liraglutide (Victoza)

Healthy eating

Mediterranean diet consist of:

  • Fresh fruits and vegetables
  • Whole grains
  • Nuts and seeds
  • Lean protein
  • Legumes
  • Dairy (small amounts)
  • Healthy fast (olive oil)
  • Avoiding processed foods, sugar, excessive red meat

DASH (Dietary approaches to stop HPT and maintain weight loss):

  • Low sodium foods (<1 teaspoon salt or <2.3g a day)
  • Higher potassium, calcium and magnesium foods
  • High fiber foods (whole grains, vegetable, fruits)

Whole food diet

  • Avoid processed/refined/bleached/hydrogenated foods
  • Less preservatives/chemicals (benzoates/sorbates), artificial food dyes

Plant based or raw diet

  • Include vegetarian, pescatarian, flexitarian and vegan diet