bariatric surgery bariatric surgery bariatric surgery (or weight loss surgery) is the medical term for a variety of procedures dealing with obesity. long term weight loss through the standard of care procedures (roux en-y bypass, sleeve gastrectomy, and biliopancreatic diversion with duodenal switch) is largely achieved by altering gut hormone levels responsible for hunger and satiety, leading to a new hormonal weight set point. bariatric surgery is the most effective treatment causing weight loss and reducing complications of obesity. bariatric surgeryother namesweight loss surgerymeshd050110 part of a series onhuman body weight general concepts obesity (epidemiology) overweight underweight body shape weight gain weight loss gestational weight gain diet (nutrition) weight management overnutrition childhood obesity (epidemiology) medical concepts adipose tissue classification of obesity genetics of obesity metabolic syndrome (epidemiology of metabolic syndrome) metabolically healthy obesity obesity paradox set point theory measurements body adiposity index body mass index body fat percentage body shape index corpulence index lean body mass relative fat mass waist–hip ratio waist-to-height ratio related conditions diabetes (type 1) eating disorder (anorexia • bulimia • binge eating disorder) food addiction hyperthyroidism malnutrition red-s starvation (starvation response) pcos obesity-associated morbidity arteriosclerosis atherosclerosis fatty liver disease gerd gynecomastia heart disease hypertension obesity and cancer osteoarthritis prediabetes sleep apnea type 2 diabetes management of obesity anti-obesity medication bariatrics bariatric surgery dieting (list of diets) caloric deficit exercise (outline) liposuction obesity medicine weight loss camp weight loss coaching yo-yo effect social aspects comfort food fast food (criticism) fat acceptance movement fat fetishism health at every size hunger obesity and the environment obesity and sexuality sedentary lifestyle social determinants of obesity social stigma of obesity weight cutting weight class as of october 2022, the american society of metabolic and bariatric surgery (asmbs) and international federation for the surgery of obesity (ifso) recommend bariatric surgery for adults with a body mass index (bmi) >35, regardless of obesity-associated conditions, and recommend considering surgery for people with bmi 30.0-34.9 who have metabolic disease. this is a recent change in guidelines (october 2022), so other guideline-producing organizations and health insurance plans may take time before their guidelines are updated. bariatric surgery can have significant health benefits in addition to weight loss, including improvement in cardiovascular risk factors, fatty liver disease, diabetes management, and reduction in mortality. long-term studies from 2009 show the procedures result in significant long-term loss of weight, recovery from diabetes, improvement in cardiovascular risk factors, and a mortality reduction from 40% to 23%. a meta-analysis in 2021 found that bariatric surgery was associated with 59% and 30% reduction in all-cause mortality among obese adults with or without type 2 diabetes, respectively. this meta-analysis also found that median life-expectancy was 9.3 years longer for obese adults with diabetes who received bariatric surgery as compared to routine (non-surgical) care, whereas the life expectancy gain was 5.1 years longer for obese adults without diabetes. a 2013 national institute of health symposium summarizing available evidence found a 29% mortality reduction, a 10-year remission rate of type 2 diabetes of 36%, fewer cardiovascular events, and a lower rate of diabetes-related complications in a long-term, non-randomized, matched intervention 15–20 year follow-up study, the swedish obese subjects study. the symposium also found similar results from a utah study using more modern gastric bypass techniques, though the follow-up periods of the utah studies are only up to seven years. while randomized controlled trials of bariatric surgery exist, they are limited by short follow-up periods. the risk of death in the period following surgery is less than 1 in 1,000. physiology each type of procedure exerts its effects through at least one of three mechanisms: restricting food intake, decreasing nutrient absorption, or affecting the body's cell signaling pathways. often, procedures affect several of these mechanisms; restricting food intake this is accomplished by reducing the size of the stomach that is available to hold a meal, (for example, gastric sleeve or stomach folding, see below). filling the stomach faster enables an individual to feel more full after a smaller meal. decreasing nutrient absorption some procedures work by reducing the amount of intestine that food passes through. for example, a roux-en-y gastric bypass connects the stomach to a more distal part of the intestine, which reduces the ability of the intestines to absorb nutrients from the food. affecting cell signaling pathways while bariatric procedures may have initially been targeted at reducing intake and absorption, studies have shown additional affects on the hormones that dictate hunger (e.g. ghrelin) and satiety (leptin). this is especially important when considering the durability of weight loss compared to lifestyle changes. while diet and exercise are essential for maintaining a healthy weight and physical fitness, metabolism typically slows as the individual loses weight, a process known as metabolic adaptation. thus, efforts for obese individuals to lose weight often stall, or result in weight re-gain. bariatric surgery is thought to affect the weight "set point," leading to a more durable weight loss. this is not completely understood, but may involve the cell-signaling pathways and hunger/satiety hormones. medical uses bariatric surgery has proven to be the most effective obesity treatment option for durable weight loss. along with this weight reduction, the procedure has significant health benefits ranging from reduced cardiovascular risk factors, remission of type 2 diabetes, reduced fatty liver disease, lower incidence and severity of depression syndromes, among others. while often effective, numerous barriers to shared decision making between the medical provider and patient include lack of insurance coverage or understanding how it functions, a lack of knowledge about procedures, conflicts with organizational priorities and clarity with care coordination, and medical training and support with using patient tools. indications historically, eligibility for bariatric surgery was defined as a bmi >40, or a bmi >35 with an obesity associated comorbidity—based on the 1991 nih consensus statement. in the three decades that followed, obesity rates have continued to rise, laparoscopic surgical techniques have made the procedure more safe, and high-quality research studies have shown the procedure's effectiveness at improving health across a variety of conditions. thus, in october 2022, asmbs/ifso put forward a revised eligibility criteria, which now includes all adult patients with bmi>35, and those with bmi >30 with metabolic disease. as of 2019, the american academy of pediatrics has recommended bariatric surgery without age-based eligibility limits under the following indications: bmi >35 with severe comorbidity, such as obstructive sleep apnea (apnea-hypopnea index >.5), type 2 diabetes mellitus, idiopathic intracranial hypertension, nonalcoholic steatohepatitis, blount disease, slipped capital femoral epiphysis, gastroesophageal reflux disease, and idiopathic hypertension or a bmi >40 kg/m2 without comorbidities. surgery is contraindicated with a medically correctable cause of obesity, substance abuse, concurrent or planned pregnancy, eating disorder, or inability to adhere to postoperative recommendations and mandatory lifestyle changes. when counseling a patient on bariatric procedures, providers should take an interdisciplinary approach. psychiatric screening is also critical for determining postoperative success. patients with a body-mass index of 40 kg/m2 or greater have a 5-fold risk of depression, and half of bariatric surgery candidates are depressed. some people with disordered eating may not be able to follow post-operative dietary guidelines. weight loss in adults, the malabsorptive procedures lead to more weight loss than the restrictive procedures; however, they have a higher risk profile. a 2005 meta-analysis from university of california, los angeles, reported the following weight loss at 36 months: biliopancreatic diversion — 53.1 kg (117 lb), roux-en-y gastric bypass (rygb) — 41.46 kg (91.4 lb), open — 41.58 kg (91.7 lb), laparoscopic — 38.32 kg (84.5 lb), vertical banded gastroplasty — 32.03 kg (70.6 lb). in children and teens, evidence for the effectiveness of bariatric surgery is more context-specific. a 2017 meta-analysis found bariatric surgery to be effective for weight loss in adolescents 36 months after the intervention and that additional data was needed to determine whether it is also effective for long-term weight loss in adolescents. according to the canadian agency for drugs and technologies in health, the comparative evidence base for bariatric surgery in adolescents and young adults was as of 2016 "...limited to a few studies that were narrow in scope and with relatively small sample sizes." type 2 diabetes mellitus type 2 diabetes is characterized by the body's resistance to the hormone insulin, which results in high blood sugars and a range of complications including increased risk of heart attack, retinopathy, kidney failure, and peripheral neuropathy. recent studies have shown that patients who have undergone bariatric surgery can often maintain their blood sugars within acceptable levels while discontinuing their diabetes medications. this may essentially amount to a 'cure' for diabetes. prior to the updated guidelines asmbs/ifso, international diabetes organizations had recommended considering bariatric surgery in people with a bmi over 30 who have type 2 diabetes and poorly controlled hyperglycemia. reduced mortality and morbidity a meta-analysis of 174,772 participants published in the lancet in 2021 found that bariatric surgery was associated with 59% and 30% reduction in all-cause mortality among obese adults with or without type 2 diabetes respectively. this meta-analysis also found that median life-expectancy was 9.3 years longer for obese adults with diabetes who received bariatric surgery as compared to routine (non-surgical) care, whereas the life expectancy gain was 5.1 years longer for obese adults without diabetes. bariatric surgery in older patients has also been a topic of debate, centered on concerns for safety in this population; the relative benefits and risks in this population is not known. fertility and pregnancy the position of the american society for metabolic and bariatric surgery as of 2017 was that it was not clearly understood whether medical weight-loss treatments or bariatric surgery had an effect responsiveness to subsequent treatments for infertility in both men and women. bariatric surgery reduces the risk of gestational diabetes and hypertensive disorders of pregnancy in women who later become pregnant but increases the risk of preterm birth. mental health among the patients who seek bariatric surgery, pre-operative mental health struggles are common. some studies have suggested that psychological health can improve after bariatric surgery, due in part to improved body image, self-esteem, and change in self-concept—these findings were also present in pediatric populations. bariatric surgery has consistently been associated with postoperative decreases in depressive symptoms and reduced severity of symptoms. importantly, the surgery may not affect everyone the same way, and there are potential adverse effects outlined in the next section. adverse effects weight loss surgery in adults is associated with relatively large risks and complications, compared to other treatments for obesity. the likelihood of major complications from weight-loss surgery is 4%. "sleeve gastrectomy had the lowest complication and reoperation rates of the three (main weight-loss surgery) procedures.....the percentage of procedures requiring reoperations due to complications was 15.3 percent for the gastric band, 7.7 percent for gastric bypass and 1.5 percent for sleeve gastrectomy," according to a 2012 study by the american society for metabolic and bariatric surgery. over a 10-year study while using a common data model to allow for comparisons, 8.94% of patients who received a sleeve gastrectomy required some form of reoperation within 5 years compared to 12.27% of patients who received a roux-en-y gastric bypass. both of the effects were fewer than those reported with adjustable gastric banding. as the rate of complications appears to be reduced when the procedure is performed by an experienced surgeon, guidelines recommend that surgery be performed in dedicated or experienced units. it has been observed that the rate of leaks was greater in low volume centres whereas high volume centres showed a lesser leak rate. leak rates have now globally decreased to a mean of 1-5%. postoperative complications laparoscopic bariatric surgery requires a hospital stay of only one or two days. short-term complications from laparoscopic adjustable gastric banding are reported to be lower than laparoscopic roux-en-y surgery, and complications from laparoscopic roux-en-y surgery are lower than conventional (open) roux-en-y surgery. risks of roux-en-y gastric bypass include anastomotic stenosis (narrowing of the intestine where the two segments are rejoined), marginal ulcers (ulcers near the rejoined segment), internal hernia, small bowel obstruction, kidney stones, and gall stones. sleeve gastrectomy also carries a small risk of stenosis, staple line leak, and gastro-esophageal reflux disease (also known as gerd, or heartburn). in addition to procedure-specific risks, patients also face risks to surgery in general. pulmonary embolism is another common adverse complication of bariatric surgery. pulmonary embolism occurs due