This blog provides free general information for anyone who is seeking to understand more about Metabolic Bariatric Surgery, the advantages, side effects, mid to long term complications as well as weight gain recurrence, not intended as a medical consult. Please seek proper medical advice for individual assessment and management.

Please read the other section on Bariatric Surgery Summary and Caveats of bariatric surgery for more information.

Understanding obesity as a significant and chronic health disease Globally obesity is a major public health problem. Worldwide the prevalence of obesity has tripled from 1980 to 2015 (estimated 1.9 billion people are currently obese) and obesity accounted for over 4 million deaths. Obesity is a chronic, progressive and relapsing disease with associated medical co-morbidities. *Even after successful weight loss results (with dieting or exercise alone) or surgery there will be potential for weight regain and return of medical co-morbidities with time. Obesity increases metabolic risk factors and is linked to common chronic health conditions (especially HPT, T2DM, dyslipidaemia), obstructive sleep apnoea, ischemic heart disease, fatty liver disease (NASH), chronic renal disease, depression and many others. *With weight regain some of these medical conditions (such as HPT, T2DM) may return. Obesity is a known risk factor for many cancers due to the chronic inflammation, adipokine dysregulation, insulin resistance and alteration in the immune system.  *Obesity related cancers include breast, endometrial, ovarian, liver, pancreas, biliary, colorectal, GOJ cancers and multiple myeloma. Bariatric surgery has been reported to reduce HER-2 positive breast cancers.  Obesity is a risk factor for endometrial hyperplasia and Type 1 endometrial adenocarcinoma. *Patients who had bariatric surgery obviously have a lower BMI at the time of treatment for endometrial cancer and are more likely to have minimally invasive hysterectomy.

Metabolic Bariatric Surgery Bariatric surgery is the most effective treatment for obesity and obesity related medical co-morbidities.  *Unlike conservative non operative management, bariatric surgery is more permanent (some procedures are also irreversible)  *Bariatric surgery works as a combination of restriction, changes in gut hormones secretion, bile acid metabolism, intestinal bacteria colonization and causing epigenetic changes. By 2014 the laparoscopic sleeve gastrectomy has become the most widely performed bariatric procedure in the world.  *In 2016 LSG accounts for more than 50% of all bariatric interventions. *In 2022 the OAGB and RYGBP have become the next two most common following the LSG. Treatment of obesity and associated medical conditions have a huge impact on healthcare budget to treat all the medical co-morbidities and complications mentioned above. The return on the financial investment in laparoscopic bariatric surgery procedure is recovered in 2-3 years after surgery.  *The mid/long term cost saving is in the reduction in health care cost to treat HPT, T2DM, coronary heart disease, OSA, depression and various cancers. *Bariatric surgery also helps to reduce premature cardiovascular mortality, all cause mortality and cancer incidences.  Indirect cost of obesity includes absenteeism and presenteeism (reduce productivity at work).

Metabolic bariatric surgery risks Despite the disadvantages, risk, complications and relapse after bariatric surgery it is emphasized that the benefits far outweight the risks in well selected patients. However the risk benefit ratio for each patient needs to be assessed carefully and the surgery needs to be worthwhile in terms of achieving the goals set out, especially in terms of realistic weight loss, resolution of medical co-morbidities, health/functional improvement in quality of life and extending life expectancy. For example bariatric surgery is not recommended for advanced age patient with non reversible end stage medical co-morbidities and already well established complications of obesity. For example with the chronicity of T2DM (over 5 years) and being on insulin for years or a decade, the diabetes will not be reversible. Bariatric surgery has 5- 10% serious post operative complication and 0.5% mortality rate *Revision bariatric surgery in particular have a much higher risk especially for leaks, bleeding and post op mortality Surgical complications Marginal ulcers have been reported in up to 5% after RYGBP and OAGB.  Risk for marginal ulcers include cigarette/alcohol consumption, NSAIDs or steroid use and Helicobacter pylori. *Some patients need prophylactic PPI medications for 6 months or longer to prevent marginal ulcers. *After the development of ulcers, follow up surveillance gastroscopy and PPI medications may be required for life. *Some patients may need post op gastroscopy 1 to 3 years (after sleeve or bypass) to check for ulcers, erosive oesophagitis, Barrett’s oesophagus or other pathology. Gastro-gastric fistula have been reported after RYGBP.  *This may result in marginal ulcers, abdominal pain, reflux and weight recidivism. After RYGBP internal hernia can occur in the inter-mesenteric small bowel defect and Petersen’s space, reported to occur in up to 12% of cases.  *This may lead to small bowel obstruction, ischemia, necrosis and perforation in severe cases or chronic pain, nausea/vomiting or other gut issues.  *Internal hernia in a pregnant lady may require emergency surgery and can result in maternal or fetal deaths. Internal hernia is less common after OAGB but may still occur in up to 2.8%. Rapid weight loss may lead to gallstone formation.  *It is uncertain whether ursodeoxycholic acid prophylaxis is necessary for the 6 months after surgery. Hospital re-admissions in the short and long term After RYGBP there is up to 11% representation to the emergency department. And 6% hospital re-admission rates mostly occur in the first 30 days after surgery.  *Commonly this is due to vomiting, dehydration and abdominal pain. Others report that after bariatric surgery up to 1/3 of patients represent to the emergency department and 1/5 was re-admitted in the first 90 days after surgery. After the LSG there can be intra thoracic migration of the sleeve.  *This is a unique problem with the sleeve. *The patient may require surgery to repair the hiatus hernia. Hospital emergency department presentations may also increase with time from surgery  *Maybe up to 30% within the first 3 years and for some patients ended up with multiple re-admissions to hospital.  *Commonly this is due to abdominal pain, causes may include internal hernia, small bowel obstruction, marginal ulcers at the GOJ and gall stones. *Marginal ulcers have been reported to occur from 0.5 to 16% after RYGBP. In the long term other problems such as diarrhoea, anaemia, hypoglycaemia, dumping, fatigue may be present as well.

Acid and alkaline/bile reflux After LSG the risk for denovo reflux has been reported in 20-26% and maybe up to 1/3 of cases *Risk factors include older patients, smokers, higher BMI Some of the patients may already have reflux before the sleeve  *After weight loss the reflux symptoms improved in maybe up to 1/5 of the patients *After LSG conversion to RYGBP there may be up to 75% resolution of reflux symptoms  After OAGB there may be more issues with micronutrient deficiencies and bile reflux compare to the sleeve and RYGBP *GOR have been reported in up to 30% after OAGB *Bile reflux resistant to medical treatment may need correctional surgery to a RYGBP with or without pouch resizing/shortening, Braun’s jejuno-jenunostomy or conversion to a proper Roux Y reconstruction. Reflux has also been reported after primary RYGBP in the long term as well *Some report 50% of patients may have recurrent GERD at 10 years follow up after RYGBP *Often patients need a CT scan to check for hiatus hernia, small bowel obstruction and internal hernia as well as a gastroscopy to check for marginal ulcers or anastomotic strictures Macro and micronutrient deficiencies after bariatric surgery Some report up to 1/3 bariatric surgery (bypass or malabsorptive procedures) patients may develop post prandial hyperinsulinaemic hypoglycemia and severe cases in up to 12% of patients.  *Hypoglycemia may contribute to weight regain with time due to cravings and the need to eat frequently  *This is more likely to occur in the younger female population group, greater amount of post op weight loss and those with higher insulin sensitivity.  *Diagnosis is difficult requiring a mixed meal provocation test and patients meeting the Whipple’s triad. Micronutrient deficiencies are often reported with RYGBP and OAGB, mainly for iron, ferritin, B12, D and iPTH.  *Worst with OAGB (see below) OAGB has been reported to have more diarrhoea, steatorrhoea, nutritional deficiencies and bile reflux oesophagitis (especially after 1 year) and revisional surgery is required in severe cases. Recent multicentre trial reported non inferiority weight loss results with OAGB (YOMEGA) compared to RYGBP, with comparable resolution of metabolic disorders.  *But the prevalence of nutritional disorders is higher in OAGB (21% of cases).  *Other reports more anaemia (44% vs 17%), hypoalbuminaemia (32% vs 15%) and hypocalcemia (19% vs 8%) comparing OAGB to RYGBP. *Protein energy malnutrition have been reported in the OAGB with a longer BP length limb over 150-200cm.  Hair loss in younger women may be associated with low levels of Zinc, folic acid and ferritin +/- iron.  *Hair loss may occur in up to 40-60% of post op patients after massive rapid weight loss in the first 6 months after LSG and gastric bypass.  *Hair loss may decrease with time. Micronutrient deficiencies can also occur after LSG not just for the bypass patients. *After LSG it has been reported that there may be deficiencies in vitamin D (up to 89%), B12 (up to 26%0, iron (up to 43%) and PTH elevation (up to 39%) in the first year post op. After LSG the causes of nutritional deficiencies are not related to the bypassed intestinal segments. *The causes are multifactorial, which include reduced dietary intake, decreased gastric acid and intrinsic factor secretion, poor food choices and food intolerances. *The micronutrient are more easily corrected. Malnutrition Protein calorie malnutrition after gastric bypass or some malabsorptive operations are rare (less than 2%) but they are extremely serious.  *Liver failure and death may result in some cases. Patients with severe refractory hypoalbuminaemia may need complete reversal of the bariatric procedure. After gastric bypass multiple blood tests are required to check for macronutrient and micronutrient deficiency.  *Often blood tests (albumin, LFT) are done 3 monthly for the 1st year, 6 monthly for the 2nd year and yearly after that for life. *Patients need a great general practitioner and dietitian to care for them in the long term as a shared care model with the surgeon or hospital. The minimal requirement for micronutrient supplements includes iron, B12, folate, calcium, vitamin D, Zinc and copper for life.

Inadequate weight loss Definitions: *Insufficient weight loss refers to <50% EWL after 2 years *Weight regain refers to a regain >25% EWL from the lowest point (nadir) after surgery and this may be an indication for revision surgery The results for revision surgery for inadequate weight loss are often disappointing *Inadequate weight loss may be due to other biological/physiological factors not related to the technical aspects of the surgery The results for revision surgery for weight regain years later on the other hand may achieve better or moderate results but the weight loss result often will not be as good as the primary weight loss procedure. Also please note revision bariatric surgery have more risk and complications, especially for leaks, fistula, abscess, bleeding, etc.  *It is not to be taken lightly.  Weight regain Weight regain of 10% of maximum weight loss may not lead to worsening of diabetes, hypertension or dyslipidaemia. Weight regain >20% of maximum weight loss may lead to worsening of hypertension Weight regain >25% of maximum weight loss may lead to worsening of of diabetes and dyslipidaemia.

Inadequate/suboptimal clinical response and weight gain recurrence   Metabolic bariatric surgery is very effective for treating severe obesity and its associated medical co-morbidities   However 10-20% patients experience suboptimal clinical response and 20-35% experience weight gain recurrence   This is often multifactorial which include medical conditions, dietary non-adherence, maladaptive eating behaviour, physical inactivity, mental health issues and surgical/technical factors   Factors to consider include: *Homeostatic hunger is triggered by food deprivation (mediated by the vagus nerve and gut hormones) and microbiota driven hunger (modulated by alterations in gut hormones) *Hedonic hunger is driven by the pleasure of eating rather than metabolic need, over riding the hypothalamic control of energy balance, resulting in consumption of high fat, high sugar foods *Psychological factors such as anxiety, depressionand maladaptive eating behaviours are significant contributors to suboptimal clinical response or recurrent weight gain after surgery *Emotional eating, lack of mindful eating, poor sleep and psychiatric disorders (binge eating, bulimia, impulsive eating) are strongly associated with weight regain   Inadequate weight loss or weight regain should not be interpreted as surgical failure but points to the fact that surgical therapy alone is not the solution and additional management strategies are needed, especially lifestyle modification and obesity management medications (OMM) as well as the input psychiatric treatment are necessary   Growing evidence suggest that OMM can increase the weight loss outcomes after metabolic bariatric surgery within the first year of surgery *OMM include liraglutide, semaglutide, phentermine, topiramate, lorcaserin or naltrexone/bupropion slow release (Contrave)   Contrave is beneficial with stress induced or craving triggered eating patterns GLP-1 RA agonist is beneficial especially for patients who need additional metabolic benefits, eg. patients with T2DM     Patients with obesity are also a metabolically heterogenous group *Metabolic bariatric surgery produces the visible weight/BMI/waist circumference decrease (anthropometric measures), improvements in metabolic parameters and body composition studies *Metabolic bariatric surgery reduces systemic inflammation *Research studies reported significant improvements in composite inflammatory markers (SII, PIV, LMR) as well as traditional haematological parameters although at this stage there are no statistically significant relationship has been observed between weight loss, anthropometric measurements and inflammatory markers   Obesity related inflammation is not only dependent on adipose tissue but also other variables such as immune system activity, microbiota composition, hormonal balance, insulin sensitivity, individual genetic differences   Also dependent on dietary pattern changes, various level of physical activity and nutritional deficiency

Weight gain recurrence   Sleeve gastrectomy remains the most popular primary metabolic and bariatric procedure worldwide in 2025 *The widespread adoption is due to the favourable safety profile, technical simplicity and effectiveness in promoting weight loss and resolution of medical co-morbidities *As a primary procedure it can achieve up to 29.5% TWL after the first year   But there is also a higher rate for revisional surgery after a sleeve gastrectomy for 2 main reasons: *Inadequate weight loss or weight regain *Hiatus hernia and gastro-oesophageal reflux   Other factors (described above) should be addressed before rushing into revisional or conversion surgery   Revision surgery rates after LSG have been reported up to 20% maybe more in the future with longer follow up data. *It is estimated that more than 80% of revision bariatric surgery is for inadequate weight loss and weight regain. *Sleeve gastrectomy conversion to Roux Y gastric bypass is the standard recommendation for reflux and may offer limited or modest additional weight loss   Revision surgery is usually performed on average after 5.6 years (range 1-17 years).   Revision/conversion OAGB or RYGBP procedures almost always result in less weight loss than the primary weight loss procedure   After LSG and sometimes gastric bypass procedures for patients with a loss of restriction, the gastric pouch can be assessed with a CT fizzogram *If it is dilated (width is >4cm) the patient may request for gastric pouch resizing   Conversion LSG to OAGB is more common in some centres for weight regain. *Conversion LSG to OAGB for reflux is controversial especially because of the incidence of bile reflux, erosive oesophagitis and GOJ adenocarcinoma     Conversion LSG to RYGBP is more common for weight regain and reflux. *The risk for denovo reflux after LSG has been reported up to 20-26% *Some of the patients did have reflux before the sleeve as well *There is up to 75% resolution of reflux symptoms after LSG to RYGBP One study compared OAGB to SADI-S after LSG for weight regain (in those BMI>50) Found 80% EWL (40% TWL) with better results in the SADI group but there were no statistical differences between the two.   LSG conversion to OAGB has better weight loss (%TWL) result than RYGBP. *Most of the OAGB are planned if there are inadequate weight loss within/after the first year   Once again revision bariatric procedures are not to be taken lightly, it has less than optimal weight loss results *The risk and complications go up significantly compared to the primary procedure *The long term gut and nutritional side effects increases with time and may persist for life