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Outcomes of bariatric surgery

Outcomes of bariatric surgery
Authors:
Dana Telem, MD
Alexander J Greenstein, MD, MPH
Bruce Wolfe, MD
Section Editor:
Daniel Jones, MD
Deputy Editor:
Wenliang Chen, MD, PhD
Literature review current through: Dec 2022. | This topic last updated: Aug 08, 2022.

INTRODUCTION — Obesity is a worldwide epidemic, affecting children, adolescents, and adults [1-4]. The 2010 National Health and Examination Survey conducted by the Centers for Disease Control and Prevention demonstrated that 33.8 percent of adults in the United States and Canada are classified as obese [5-8].

Bariatric surgery and procedures remain the most effective sustained weight loss option for patients with class II or III obesity, and the performance of bariatric surgery or procedures has significantly increased in the last 10 years [9,10]. The American Society for Metabolic and Bariatric Surgery (ASMBS) estimated that in 2017 alone, 228,000 people in the United States underwent a weight loss operation [11]. Worldwide, nearly 580,000 people undergo bariatric surgery annually [12]. In addition to achieving weight loss, bariatric operations also result in marked improvement or remission of many obesity-related health problems, such as type 2 diabetes.

This topic reviews outcomes of bariatric operations in sustained weight loss, medical comorbidities, psychosocial difficulties, and health care expenditure. Additional topics on bariatric surgery are discussed separately, including:

(See "Bariatric surgery for management of obesity: Indications and preoperative preparation".)

(See "Bariatric procedures for the management of severe obesity: Descriptions".)

(See "Late complications of bariatric surgical operations".)

(See "Bariatric surgery: Postoperative nutritional management".)

(See "Laparoscopic Roux-en-Y gastric bypass".)

(See "Laparoscopic sleeve gastrectomy".)

WEIGHT LOSS — There is now ample evidence that bariatric surgery results in greater long-term weight loss than the best available nonsurgical interventions for obesity, regardless of the bariatric procedure used [13].

The advantage of bariatric surgery over nonsurgical weight management is best illustrated by the Swedish Obese Subjects (SOS) study (n = 4047; body mass index [BMI] >34 kg/m2) [14]. At 20 years, the mean total body weight loss was 26 percent after Roux-en-Y gastric bypass (RYGB), 18 percent after vertical-banded gastroplasty (a legacy procedure), 13 percent after adjustable gastric band (AGB), and 1 percent with nonsurgical management.

Metrics — Historically, the primary endpoint of bariatric surgery has been weight loss, which has been measured in several different ways:

In the surgical literature, weight loss is most often reported as a percentage of excess body weight (calculator 1). Excess body weight is defined as the amount of weight that is in excess of the ideal body weight. Ideal body weight is conventionally determined by the Metropolitan Life Tables [15] or the method of Devine (calculator 2). This table shows the expected short-term weight loss following individual bariatric procedures as the percentage of excess weight lost for patients undergoing an RYGB, sleeve gastrectomy (SG), or AGB procedure (table 1) [16,17]. Bariatric outcomes have also been described in BMI lost and percentage BMI lost (calculator 1).

In the medical literature, weight loss is also reported as a percentage of the actual body weight (calculator 1). In a retrospective study of over 65,000 patients in the National Patient-Centered Clinical Research Network (PCORnet), one-year mean percent total weight loss was 31.2 percent (95% CI 31.1-31.3) for RYGB, 25.2 percent (95% CI 25.1-25.4) for SG, and 13.7 percent (95% CI 13.3-14.0) for AGB; five-year mean percent total weight loss was 25.5 percent (95% CI 25.1-25.9) for RYGB, 18.8 percent (95% CI 18.0-19.6) for SG, and 11.7 percent (95% CI 10.2-13.1) for AGB [18]. However, 30 day rates of major adverse events were 5.0 percent for RYGB, 2.6 percent for SG, and 2.9 percent for AGB.

While excess body weight has been used to report surgical weight loss, it has been increasingly replaced by percentage of total body weight loss. This change has been prompted by the need to stay consistent with the medical literature, which virtually never reports excess body weight, and to avoid the use of ideal body weight, which has been inconsistently defined.

Initial weight loss — Weight loss is highly variable following each bariatric surgical procedure [19]. Trials comparing procedures have generally shown that patients undergoing RYGB and SG have similar weight loss [20,21], while both of those procedures resulted in greater weight loss than AGB [22,23].

BPD — In most published series, biliopancreatic diversion (BPD) provides the most significant weight loss but also the highest complication rate. As an example, a retrospective review of the Bariatric Outcomes Longitudinal Database from 2007 to 2010 reported a greater two-year percent excess weight loss of BPD compared with RYGB (79 versus 67 percent) but also longer operative times, greater blood loss, longer hospital stay, and higher early reoperation rates [24]. (See "Bariatric procedures for the management of severe obesity: Descriptions", section on 'Biliopancreatic diversion with duodenal switch'.)

RYGB and SG — The weight loss achieved by any intervention, including surgery, is highly variable. For patients undergoing RYGB or SG, weight loss occurs rapidly over the first few months, then continues over the next year to year and a half until weight loss reaches a plateau. During the first six months after RYGB, the average weight loss is 10 to 15 pounds (4.5 to 7 kg) per month. Thus, average weight loss at six months is 60 to 80 lb (27 to 36 kg). Thereafter, the rate of weight loss tends to slow down to 5 to 7 lb (2 to 3 kg) per month, and total weight loss reaches a peak at 12 months postoperatively, averaging 100 to 120 lb (45 to 54 kg).

As the popularity of SG has increased substantially, its efficacy in promoting weight loss has been measured against RYGB in multiple randomized trials:

In a Swiss multicenter randomized trial (SM-BOSS) of 217 patients with BMI between 35 and 61 kg/m2, there was no significant difference in weight loss at one, two, or five years after RYGB compared with SG [20]. At five years, patients maintained 61.1 percent excess BMI loss with SG versus 68.3 percent excess BMI loss with RYGB. Overall, 16 of 101 patients (15.8 percent) who underwent SG required a reoperation (9 of 16 for severe gastroesophageal reflux disease [GERD]), while 23 of 104 patients (22.1 percent) who underwent RYGB required a reoperation (9 of 23 for internal hernia). There were no significant differences in major medical outcomes (eg, remission of diabetes, dyslipidemia, and hypertension), except that GERD symptoms improved significantly in patients who had undergone RYGB but worsened in patients who had undergone SG [25]. (See 'Gastroesophageal reflux disease' below.)

In a Finnish multicenter randomized trial (SLEEVEPASS) of 240 patients with severe obesity, patients who had undergone RYGB had slightly greater percent excess weight loss (EWL) than patients who had undergone sleeve gastrectomy at all points. At 10 years, percent EWL was 43.5 percent after SG versus 50.7 percent after RYGB; the difference of 8.4 percent (95% CI, 3.1-13.6) was statistically significant [26]. After SG and RYGB, there was no statistically significant difference in the remission rate of type 2 diabetes (26 versus 33 percent), dyslipidemia (19 versus 35 percent), or obstructive sleep apnea (16 versus 31). Hypertension remission was superior after RYGB (8 versus 24 percent). Esophagitis was more prevalent after SG (31 versus 7 percent) with no statistically significant difference in Barrett esophagus (4 versus 4 percent). The overall reoperation rate was 15.7 percent after SG and 18.5 percent after RYGB.

Although the two randomized trials drew different conclusions because of different study designs, it is clear from the data that the efficacies of SG and RYGB are quite similar: there was only a 1 BMI unit difference in weight loss between the two procedures at five years, which may not be clinically meaningful, and there was no significant difference in diabetes remission rates in either trial [27]. SG and RYGB, however, differ in complication profiles: most of the reoperations after SG were for severe GERD, and those after RYGB for internal hernias; GERD symptoms worsened after SG but improved after RYGB. Given the relative parity between these procedures in promoting weight loss and comorbidity remission, the choice of SG versus RYGB may depend upon which potential risk or consequence is more acceptable to the patient [28].

By contrast, RYGB patients generally achieve slightly greater weight loss than SG patients in observational studies [18,29-31]. In the PCORnet study [18], the reported five-year difference in percent total weight loss was 6.7 (5.8 to 7.7) percent, which may reflect unmeasured differences in patient and surgeon preferences; patients' attitudes, motivations, and behaviors; as well as surgical technique [13].

SG and RYGB are discussed in detail in other topics:

(See "Laparoscopic Roux-en-Y gastric bypass".)

(See "Laparoscopic sleeve gastrectomy".)

AGB — For patients who undergo an AGB procedure, weight loss is slower, with an anticipated one pound per week weight loss until stabilization is reached at approximately two years [16,17].

In the multicenter longitudinal (Longitudinal Assessment of Bariatric Surgery [LABS]) study, seven-year mean weight loss after AGB was 18.8 kg (95% CI 16.3-21.3), or 14.9 percent (95% CI 13.1 to 16.7 percent) of the baseline weight. The mean weight regain between year 3 and 7 was 1.4 percent (95% CI 0.4 to 2.4 percent) of the baseline weight [32].

Although most patients do well initially, most ultimately fail to sustain their improvement [33]. Some AGB patients may not ever achieve significant weight loss. This highlights the importance of establishing a fundamental lifestyle change during the first one to two years after surgery in order to achieve long-term success in maintaining weight loss. Because of its poor efficacy, AGB is rarely performed in contemporary bariatric practice. (See "Bariatric procedures for the management of severe obesity: Descriptions", section on 'Laparoscopic adjustable gastric banding'.)

Durable weight loss — The durability of weight loss following bariatric surgery is crucial to its acceptance by the general public. In a systematic review and meta-analysis of studies with 10 or more years of follow-up, 18 reports of RYGB showed a weighted mean of 56.7 percent of EWL, 17 reports of AGB showed 45.9 percent EWL, 9 reports of BPD showed 74.1 percent EWL, and 2 reports of SG showed 58.3 percent EWL [34].

Regardless of the procedure, most patients will regain some weight over time, usually beginning in the second postoperative year. In the first decade after surgery, patients typically regain 5 to 10 percent of their total body weight. As examples, in the Swedish Obese Subjects (SOS) study, total weight loss (TWL) decreased from 32 to 25 percent within 10 years after RYGB [35]; in the Longitudinal Assessment of Bariatric Surgery (LABS) study, TWL decreased from 35 to 28 percent within seven years after RYGB [32]; in a third large long-term study, TWL decreased from 35 to 27 percent within 12 years after RYGB [36].

Although some weight regain after bariatric surgery is common, excessive weight regain in some patients can be problematic. However, what constitutes excess or significant weight regain after bariatric surgery is not uniformly defined. In the literature, weight regain after bariatric surgery has been variably defined as [37-39]:

Any weight increase from the nadir, or weight increase in excess of a set threshold above the nadir (eg, 10 kg).

In terms of percent excess weight loss (eg, <25 or 50 percent excess weight loss, or >25 percent excess weight gain from nadir).

In terms of percent total body weight (eg, >15 percent total body weight gain from nadir).

In terms of BMI (eg, >BMI increase of 5 kg/m2 from nadir, or regain to BMI >35 kg/m2 after success loss).

Another way to compare weight regain across procedures is to consider the proportion of patients who regain weight to the point that they are within 5 percent or less of their preoperative weight. Two studies with follow-ups of four to five years estimated that risk to be 2.5 to 3.3 percent after RYGB, 12.5 to 14.5 percent after SG, and 30.5 to 36 percent after AGB [18,29].

Some definitions of weight regain have been correlated with deterioration in health-related quality of life or comorbid conditions, but only in specific patient populations [37]. In a meta-analysis of 51 studies that included inadequate weight loss or weight regain as an indication for revisional bariatric surgery, 31 studies gave no criteria, seven studies quoted <50 percent of excess weight loss at 18 months as the criteria for reoperation, and six studies used <25 percent of excess weight loss as the criteria [40].

METABOLIC EFFECTS — Besides weight loss, bariatric surgery is most studied for its metabolic effect. The metabolic syndrome is defined as the co-occurrence of metabolic risk factors for both type 2 diabetes and cardiovascular disease (ie, abdominal obesity, hyperglycemia, dyslipidemia, and hypertension). (See "Metabolic syndrome (insulin resistance syndrome or syndrome X)".)

Bariatric surgery induces significant, durable weight loss and ameliorates metabolic syndrome in all three of its components, hyperglycemia/type 2 diabetes, hypertension, and dyslipidemia, all risk factors for cardiovascular disease. Consequently, the risk of cardiovascular disease is lowered after bariatric surgery.

Diabetes mellitus — Type 2 diabetes and obesity often coexist. An estimated 85 percent of all patients with type 2 diabetes are either overweight or obese by body mass index (BMI) criteria [41]. For obese diabetic patients who fail lifestyle management and medical therapy, bariatric surgery is the most effective treatment and can achieve long-term remission in 23 to 60 percent of patients, depending on the baseline severity and duration of their diabetes [42].

Bariatric surgery has been shown to exert profound glucoregulatory effects potentially via neuroendocrine mechanisms [42]. Improvement in glycemic control is often evident within days to weeks following surgery, most likely reflecting an alteration in gastrointestinal physiology that is independent of weight loss [43]. A glucagon-like peptide-1 (GLP-1) mediated mechanism has been implicated [44,45], among others.

Prevention — In a French national survey of over 300,000 patients with obesity between 2008 and 2016, the approximately 100,000 patients who underwent bariatric surgery were far less likely to develop type 2 diabetes (2 versus 13 percent; hazard ratio [HR] 0.18, 95% CI 0.17-0.19) or develop type 2 diabetes complications than controls [46]. Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) were more protective against diabetes (1.2 versus 0.9 versus 4.5 percent), as well as diabetes-related complications, compared with adjustable gastric band (AGB).

Efficacy — During the past decade, the anti-diabetes efficacy of bariatric surgery has been compared with that of medical therapy in a dozen or more trials [47-55], in which bariatric surgical procedures were performed laparoscopically (RYGB 9 trials; AGB 5 trials; SG 2 trials; biliopancreatic diversion with duodenal switch [BPD-DS] 1 trial); medical therapy included lifestyle changes, weight management counseling, home glucose monitoring, and drug therapy as defined by the American Diabetes Association [56,57]. (See "Overview of general medical care in nonpregnant adults with diabetes mellitus".)

All but one trial found bariatric surgery superior to medical therapy in reaching the predesignated glycemic target [13,42]. Overall, surgery decreased HbA1c by 2 to 3.5 percent, compared with 1 to 1.5 percent achieved medically. Most trials also favored surgery in secondary endpoints such as weight loss and remission of metabolic syndrome. A meta-analysis of seven trials found that RYGB led to higher rates of diabetes remission than medical therapy at one, three, and five years, as well as higher rates of achieving the American Diabetes Association's (ADA's) composite goal at one, two, three, and five years [58]. Nearly all trials also included patients with BMIs between 30 and 35 kg/m2 and showed that surgery (especially RYGB and SG) was just as effective for them as for heavier patients [59].

A 2009 meta-analysis of 19 mostly observational studies with one to three years of follow-up reported a remission rate of 78 percent and an improvement rate of 87 percent for type 2 diabetes with one- to three-year follow-up [60]. Remission is defined as reaching an HbA1c target at or below 6 to 6.5 percent without the help of diabetes medications. Surgery was also significantly more effective than medical therapy in preventing de novo type 2 diabetes (relative risk reduction of 78 percent).

In a 2011 prospective, longitudinal study that included bariatric-specific data from more than 100 participating institutions and 28,616 obese diabetic patients, remission or improvement in diabetes at 12 months was achieved in 83 percent of patients undergoing RYGB, 55 percent undergoing SG, and 44 percent undergoing an AGB [61].

In a database study of 8546 Swedish patients with type 2 diabetes who underwent bariatric surgery between 2007 and 2015, 58 and 47 percent achieved complete diabetes remission after two and five years, respectively. Remission rate was inversely related to the duration of diabetes and was highest among those with recent onset and non-insulin-dependent diseases [62].

In most contemporary series, the efficacies of RYGB and SG are regarded as comparable [63], whereas metabolic control following AGB is less effective and occurs later in the postoperative period. Two trials mentioned above reported no significant difference in weight loss or diabetes remission between RYGB and SG at five years [20,21], while most but not all observational studies found higher rates of type 2 diabetes remission with RYGB than SG [64,65]. (See 'RYGB and SG' above.)

Durability — The durability of glycemic control after bariatric procedures has been another subject of intense interest. In a multicenter longitudinal study (Longitudinal Assessment of Bariatric Surgery [LABS]), among patients with diabetes at baseline, the remission rates at one, three, five, and seven years were 71.2, 69.4, 64.6, and 60.2 percent, respectively, after RYGB and 30.7, 29.3, 29.2, and 20.3 percent, respectively, after AGB [32]. The rate of new-onset diabetes at all follow-up assessments was <1.5 percent after RYGB.

In a French population-based case-control study that included over 30,000 patients, at six years, those who underwent bariatric surgery (AGB, SG, or RYGB) were more likely to discontinue (-50 versus -9 percent) and less likely to initiate antidiabetes medications (1.4 versus 12 percent) compared with matched patients who did not have bariatric surgery [66]. Patients who underwent RYGB were more likely to discontinue antidiabetes medications than patients who underwent SG and AGB.

Two of the trials that compared surgical with medical therapy have reported five-year data:

Patients with BMIs of 27 to 43 and uncontrolled type 2 diabetes undergoing an RYGB (n = 50) or an SG (n = 49) plus medical therapy were significantly more likely to achieve the main outcome of a glycated hemoglobin level of 6.0 percent or less at 12 months compared with patients managed by intensive medical therapy alone (n = 41) (42 versus 37 versus 12 percent, respectively) [48]. Data at three and five years are consistent with these one-year results [49,50]. The pre-trial mean glycated hemoglobin level was 9.2±1.5 percent.

A randomized trial of 60 patients, using different entry criteria and surgical procedures, also found that obese diabetic patients undergoing a bariatric operation had better control than medical management alone. Patients with BMI ≥35, a history of diabetes for five or more years, and a glycated hemoglobin level ≥7.0 percent undergoing an RYGB or BPD were more likely to achieve the study endpoint of remission of diabetes at two years compared with patients managed by medical therapy alone (75 versus 95 versus 0 percent, respectively) [51]. At five years, however, 8 of 15 patients in the RYGB group and 7 of 19 patients in the BPD group developed recurrent diabetes after initially achieving remission [52]. Nevertheless, the proportion of patients who were diabetes free at five years was still higher with bariatric surgery than with medical management (50 versus 0 percent). Although surgical (RYGB and BPD) patients lost more weight than medically treated patients, weight loss did not predict diabetes remission or relapse in that study.

Finally, 10 year follow-up results have been reported after 60 patients with advanced type 2 diabetes and obesity underwent medical therapy, RYGB, or BPD in a trial [51]. At 10 years, the remission rate of diabetes was 5.5 percent with medical therapy, 25 percent with RYGB, and 50 percent with BPD. Compared with medical therapy, surgery was associated with fewer diabetes-related complications (relative risk 0.07, 95% CI 0.01-0.48), but BPD (odds ratio 2.7, 95% CI 1.3-5.6), though not RYGB, was associated with more serious adverse events [67].

Diabetic complications — Macrovascular disease, such as coronary artery disease and cerebral vascular events, is a leading cause of morbidity and mortality for patients with type 2 diabetes. The beneficial effect of metabolic surgery on diabetic macrovascular complications has been documented in several large retrospective studies but not randomized trials.

In a retrospective study comparing bariatric procedures (76 percent RYGB, 17 percent SG, and 7 percent AGB) against medical treatment for diabetes in over 20,000 matched obese adults, bariatric surgery was associated with a lower composite incidence of macrovascular events at five years (2.1 percent in the surgical group versus 4.3 percent in the nonsurgical group), as well as a lower incidence of coronary artery disease (1.6 percent in the surgical group versus 2.8 percent in the nonsurgical group) [68]. The incidence of cerebrovascular disease was not significantly different (0.7 percent in the surgical group versus 1.7 percent in the nonsurgical group).

In a retrospective study comparing 2287 diabetic patients who underwent metabolic surgery (63 percent RYGB, 32 percent SG) with 11 ,435 matched obese diabetic controls, metabolic surgery was associated with a lower risk of major adverse cardiovascular events (MACE), including mortality (cumulative incidence at 8 years 10 versus 17.8 percent; odds ratio [OR] 0.59, 95% CI 0.48-0.72), heart failure (6.8 versus 18.9 percent; OR 0.38, 95% CI 0.30-0.49), coronary artery disease (7.9 versus 11.6 percent; OR 0.68, 95% CI 0.54-0.87), cerebrovascular disease (4.1 versus 5.6 percent; OR 0.67, 95% CI 0.48-0.94), nephropathy (6.3 versus 16.3 percent; OR 0.41, 95% CI 0.31-0.52), and atrial fibrillation (7.9 versus 13.6 percent; OR 0.78, 95% CI 0.62-0.97) [69].

In a meta-analysis of 6 trials and 13 nonrandomized studies, bariatric surgery was associated with reduced mortality (OR 0.34, 95% CI 0.25-0.46) and macrovascular complication rates (OR 0.38, 95% CI 0.22-0.67) compared with medical therapy for type 2 diabetes [70].

Diabetes is also one of the most important causes of end-stage kidney disease (nephropathy), adult blindness (retinopathy), and peripheral neuropathy, referred to collectively as microvascular diseases.

In a retrospective case-control study of over 15,000 obese adults with type 2 diabetes, bariatric surgery (76 percent RYGB, 17 percent SG, 7 percent AGB) was associated with half the incidence of microvascular disease at five years compared with usual medical care (17 versus 35 percent) [71]. The reduction is primarily driven by a lower rate of neuropathy (7 versus 21 percent), but the incidences of nephropathy (5 versus 10 percent) and retinopathy (7 versus 11 percent) were also reduced with bariatric surgery.

In a trial of 100 patients with type 2 diabetes, obesity (BMIs of 30 to 35 kg/m2), and stage G1 to G3 and A2 to A3 chronic kidney disease (urinary albumin-creatinine ratio [uACR] >30 mg/g and estimated glomerular filtration rate >30 mL/min), RYGB resulted in greater rate of remission of both albuminuria (82 versus 55 percent) and chronic kidney disease (82 versus 48 percent) compared with best medical management at two years [72].

In a meta-analysis of 12 studies involving more than 32,000 patients with obesity and type 2 diabetes, those who underwent metabolic surgery had a lower incidence rate of microvascular diseases (OR 0.34, 95% CI 0.30-0.39) than those treated medically. Specifically, metabolic surgery reduced the incidence of diabetic nephropathy (OR 0.39, 95% CI 0.30-0.50), diabetic retinopathy (OR 0.52, 95% CI 0.42-0.65), and diabetic neuropathy (OR 0.27, 95% CI 0.22-0.34) [73].

Diabetic patients who do not need insulin, or with shorter-duration type 2 diabetes or lower HbA1c, appear to have better outcomes after bariatric surgery than those with more advanced-stage diabetes [74-76]. These studies suggest that bariatric surgery should not be delayed until type 2 diabetes is poorly controlled on multiple medications. However, more trials are needed to establish the long-term benefits and safety of early intervention.

There is evidence that even if adults with diabetes relapse, transient periods of improved control may confer benefits for long-term microvascular complications. Such beneficial effects of improved glycemic control have been termed the "legacy effect" or "metabolic memory" [77]. In a retrospective study, patients who achieved diabetes remission after bariatric surgery had a 29 percent lower risk of developing microvascular complications, and for every additional year of time in remission prior to relapse, the risk of microvascular disease was reduced by 19 percent compared with those who never remitted, thereby supporting the legacy effect of bariatric surgery [78].

Further discussion on complications of diabetes is reviewed separately. (See "Epidemiology and classification of diabetic neuropathy" and "Screening for diabetic polyneuropathy" and "Management of diabetic neuropathy".)

Candidates for "metabolic surgery" — For two decades, bariatric surgery was only performed for indications specified by the 1991 National Health Institute (NIH) consensus conference [79]. The goal of surgery was weight loss, and patients must have a BMI greater than 40 kg/m2, or greater than 35 kg/m2 and significant comorbidities, to qualify. (See "Bariatric surgery for management of obesity: Indications and preoperative preparation", section on 'Indications'.)

The 2013 guidelines published by the American Heart Association (AHA), American College of Cardiology (ACC), and The Obesity Society (TOS) were largely unchanged, stating that there was insufficient evidence to recommend bariatric or metabolic surgical procedures as primary treatment for type 2 diabetes independent of BMI criteria [80,81].

In 2015, the second Diabetes Surgery Summit (DSS-II) Consensus Conference published guidelines that have been endorsed by more than 50 diabetes and medical organizations [82]. These guidelines support the use of metabolic surgery and further expanded its indications to that of a treatment for type 2 diabetes in patients with a BMI between 30 and 34.9 kg/m2 (27.5 to 32.4 kg/m2 for the Asian population), if hyperglycemia is inadequately controlled by oral or injectable medications (algorithm 1). The 2018 Standards of Care for Diabetes from the American Diabetes Association included this in the recommendations [83]. Bariatric surgery used with the primary intent to treat diabetes or metabolic syndrome is referred to as "metabolic surgery."

Hypertension — The association between obesity and the development of hypertension is well established. Sixty-four percent of adults with severe obesity seeking bariatric surgery have hypertension [32]. (See "Overweight, obesity, and weight reduction in hypertension".)

Weight loss, whether by an intensive lifestyle-medical modification program or a bariatric operation, improves obesity-linked hypertension or contributes to its remission.

The benefit of bariatric surgery is best illustrated by a trial (GATEWAY) of 100 patients with hypertension (using ≥2 antihypertensive medications) and obesity (BMI 30.0 to 39.9 kg/m2), in which blood pressure was the primary endpoint [84]. RYGB plus medical therapy reduced antihypertensive drug use by ≥30 percent in more patients compared with medical therapy alone at one year (84 versus 13 percent) and three years (73 versus 11 percent), and a greater number of surgical patients achieved remission of hypertension at one year (46 to 51 versus 0 percent) and three years (31 to 35 versus 0 to 2 percent) [84,85]. Whereas weight decreased gradually after RYGB, its effect on hypertension was fully achieved in the first month. In addition, surgical patients had less daily ambulatory blood pressure variability and a lower prevalence of resistant hypertension (0 versus 15 percent) [86].

In a single-center registry-based cohort study from Norway, hypertension was the primary outcome compared among 932 patients with obesity undergoing bariatric surgery (92 percent RYGB; 8 percent SG) and 956 control patients treated medically. At a median follow-up of 6.5 years, surgically treated patients had a greater likelihood of remission (31.9 versus 12.4 percent) and lesser likelihood for new onset of hypertension (3.5 versus 12.2 percent) [87].

In another Swedish national registry-based study of 15,984 patients with hypertension who underwent bariatric surgery, 39.2 percent were in remission at two years; greater weight loss and male sex were associated with greater chance of remission [88]. The 10 year cumulative probability of major adverse cardiovascular event and all-cause mortality were both lower after achieving remission at two years, despite a substantial relapse rate.

Several other trials also found a reduction in antihypertensive medication use and improved blood pressure control after bariatric surgery, but the primary endpoint of those trials was diabetes rather than blood pressure control [48,51,53].

Data are mixed as to whether or not RYGB offers the greatest remission or reduction of hypertension of bariatric operations [61,89]. In a meta-analysis of 32 studies (including 6 trials), patients who underwent RYGB were more likely to have remission of hypertension at both one year (relative risk [RR] 1.14, 95% CI 1.06-1.21) and five years (RR 1.26, 95% CI 1.07-1.48) compared with those who underwent SG [90].

Dyslipidemia — Sixty-four percent of adults with severe obesity seeking bariatric surgery have dyslipidemia, including hypertriglyceridemia, decreased high-density lipoprotein cholesterol values, and/or increased low-density lipoprotein cholesterol particles [32]. Dyslipidemia is a well-established risk factor for cardiovascular disease [91]. (See "Obesity: Association with cardiovascular disease".)

Observational studies have demonstrated improved lipid profiles following bariatric procedures [53,61,92-95]. As an example, in the LABS study, the prevalence of dyslipidemia remains lower at seven years post-RYGB compared with baseline (14 versus 33 percent for high low-density lipoprotein cholesterol; 5 versus 24 percent for high triglycerides; 6 versus 35 percent for low high-density lipoprotein cholesterol) [32].

Two meta-analyses associated RYGB with greater improvement in lipid profile than SG at one to three years [96,97], although longer follow-up is required to evaluate procedure-specific differences in dyslipidemia outcomes.

Cardiovascular risk — As a result of resolved or improved cardiovascular risk factors such as diabetes, hypertension, and dyslipidemia, bariatric surgery is associated with reduced number of cardiovascular deaths and lower incidence of cardiovascular events in individuals with obesity [14,69,98]. This is based on observational data, as a 2022 systematic analysis did not identify any randomized trials; the meta-analysis of 39 prospective and retrospective cohort studies reported that [99]:

Bariatric surgery was associated with a beneficial effect on all-cause mortality (pooled HR 0.55, 95% CI 0.49-0.62) and cardiovascular mortality (HR 0.59, 95% CI 0.47-0.73).

Bariatric surgery was also associated with a reduced incidence of heart failure (HR 0.50, 95% CI 0.38-0.66), myocardial infarction (HR 0.58, 95% CI 0.43-0.76), stroke (HR 0.64, 95% CI 0.53-0.77), and atrial fibrillation (not statistically significant; HR 0.82, 95% CI 0.64-1.06, P = 0.12).

CANCER RISK AND MORTALITY — The association between obesity and certain cancers has been well established [100-104]. According to the International Agency for Research on Cancer Handbook Working Group, the 13 types of obesity-associated cancer include esophageal cancer, renal cell cancer, breast cancer (in postmenopausal or oophorectomized younger patients), gastric cardia cancer, colon cancer, rectal cancer, liver cancer, gallbladder cancer, pancreatic cancer, ovarian cancer, uterine cancer, thyroid cancer, and multiple myeloma [105]. Obesity also increases the likelihood of worse oncologic outcomes [102]. (See "Overweight and obesity in adults: Health consequences", section on 'Cancer'.)

The relationship between obesity and risk of breast, endometrial, colon, and prostate cancer is reviewed separately. (See "Factors that modify breast cancer risk in women" and "Endometrial carcinoma: Epidemiology, risk factors, and prevention", section on 'Obesity' and "Risk factors for prostate cancer", section on 'Obesity' and "Colorectal cancer: Epidemiology, risk factors, and protective factors", section on 'Obesity'.)

In a database study of over 16,000 patients, patients who underwent bariatric surgery had a decreased risk of hormone-related cancers (odds ratio [OR] 0.23, 95% CI 0.18-0.30), including breast (OR 0.25, 95% CI 0.19-0.33), endometrium (OR 0.21, 95% CI 0.13-0.35), and prostate cancer (OR 0.37, 95% CI 0.17-0.76), compared with matched patients who did not have surgery [106]. Roux-en-Y gastric bypass (RYGB) resulted in the largest risk reduction for hormone-related cancers (OR 0.16, 95% CI 0.11-0.24) but was associated with an increased risk for colorectal cancer (OR 2.63, 95% CI 1.17-5.95). Adjustable gastric band (AGB) and sleeve gastrectomy (SG) were not associated with any increased risk of colorectal cancer.

In another multisite database study, 22,000 patients who underwent bariatric surgery (61 percent RYGB and 27 percent SG) had a 33 percent lower hazard of developing any cancer during the mean follow-up period of 3.5 years compared with over 66,000 matched patients who did not undergo surgery (hazard ratio [HR] 0.67, 95% CI 0.60-0.74) [107]. Bariatric surgery was associated with a lower risk of developing postmenopausal breast cancer (HR 0.58, 95% CI 0.44-0.77), endometrial (HR 0.5, 95% CI 0.37-0.67), pancreatic (HR 0.46, 95% CI 0.22-0.97), and colon cancer (HR 0.59, 95% CI 0.36-0.97). No reduction in rectal cancer was found, which may explain the discrepancy with the study above. A French database study of over one million patients suggested that, following bariatric surgery (RYGB, SG, or AGB), patients with obesity shared the same risk of colorectal cancer as the general population, whereas for patients with obesity who did not undergo bariatric surgery, the risk is 34 percent above that of the general population [108].

In another multi-database study of 28,000 bariatric surgery-eligible patients, postoperative rates of any cancer type and lung, ovarian, and uterine cancer were significantly lower in patients undergoing either vertical sleeve gastrectomy (VSG) or RYGB compared with nonsurgical control patients [109].

In another retrospective study of 5053 patients who underwent bariatric surgery (RYGB or SG) and 25,265 matched patients in the nonsurgical control group, bariatric surgery was associated with a lower risk of obesity-associated cancer (10 year cumulative incidence 2.9 versus 4.9 percent, hazard ratio 0.68) and cancer-related mortality (10 year cumulative incidence 0.8 versus 1.4 percent, hazard ratio 0.52) [110].

Studies using the Swedish Obese Subjects (SOS) Database associated bariatric surgery with a reduction of cancer risk over 20 years from 6 to 3.9 percent, and the effect was more pronounced in women [111]. A study using the Utah Cancer Registry showed that cancer mortality was reduced by 46 percent in patients who underwent bariatric surgery [112].

Bariatric surgery has also been associated with a reduced risk of all skin cancers (adjusted sub-hazard ratio 0.59, 95% CI 0.35-0.99), including melanoma (adjusted sub-hazard ratio 0.43, 95% CI 0.21-0.87) [113].

LONG-TERM SURVIVAL — The overall all-cause mortality appeared to be reduced after bariatric surgery compared with nonsurgical management of obesity but may still be higher than that of the general population.

In a study that followed the Swedish Obese Subjects (SOS) study participants and a random sample of the general population for over 20 years, the adjusted median life expectancy of obese individuals who underwent bariatric surgery was 3.0 years (95% CI 1.8-4.2) longer than that of those who received usual obesity care but 5.5 years shorter than that in the general population [114]. Fewer patients in the surgery group died (hazard ratio [HR] 0.77, 95% CI 0.68-0.87), died from cardiovascular disease (HR 0.70, 95% CI 0.57-0.85), or died from cancer (HR 0.77, 95% CI 0.61-0.96) compared with those who received usual obesity care.

In a meta-analysis of 16 matched cohort studies and one trial totaling 174,772 participants, metabolic surgery was associated with a reduced risk of death (HR 0.492, 95% CI 0.463-0.519) and a prolongation of median life expectancy of 6.1 years (95% CI 5.2-6.9) compared with usual care [115]. Patients with diabetes benefited more from metabolic surgery than those without diabetes (9.3 versus 5.1 years gained in median life expectancy). It is estimated that every 1 percent increase in metabolic surgery utilization rate among patients with and without diabetes could yield 5.1 million and 6.6 million potential life-years saved, respectively. Treatment effects did not differ among gastric bypass, banding, and sleeve gastrectomy.

A Canadian population-based study matched 13,679 patients who underwent bariatric surgery with the same number of nonsurgical patients according to age, sex, body mass index, and diabetes duration [116]. At 4.9 years, the all-cause mortality rate (1.4 versus 2.5 percent; HR 0.68, 95% CI 0.57-0.81), cardiovascular mortality rate (HR 0.53, 95% CI 0.34-0.84), and cancer mortality rate (HR 0.54, 95% CI 0.36-0.80) were all lower in the surgery than in the nonsurgery group.

In an Israeli retrospective cohort study of over 8000 patients who underwent Roux-en-Y gastric bypass (RYGB), sleeve gastrectomy (SG), and adjustable gastric band (AGB) compared with over 25,000 matched obese but nonsurgical patients, the all-cause mortality was lower with bariatric surgery at a median follow-up of 4.3 years (1.3 versus 2.3 percent). The absolute difference was 2.51 (95% CI 1.86-3.15) fewer deaths per 1000 person-years in the surgical versus nonsurgical group. Adjusted hazard ratios for mortality among nonsurgical versus surgical patients were 2.02 (95% CI 1.63-2.52) for all procedures, 2.01 (95% CI 1.50-2.69) for AGB, 2.65 (95% CI 1.55-4.52) for RYGB, and 1.60 (95% CI 1.02-2.51) for SG [117].

In an earlier American (Utah) case-control study, the adjusted all-cause mortality of 7925 patients who underwent RYGB was 40 percent lower than that of the control group (37.6 versus 57.1 deaths per 10,000 person-years, p <0.001) at seven years; cause-specific mortality in the surgery group decreased by 56 percent for coronary artery disease (2.6 versus 5.9 per 10,000 person-years, p = 0.006), by 92 percent for diabetes (0.4 versus 3.4 per 10,000 person-years, p = 0.005), and by 60 percent for cancer (5.5 versus 13.3 per 10,000 person-years, p <0.001). However, rates of death not caused by disease, such as accidents and suicide, were 58 percent higher in the surgery group than in the control group (11.1 versus 6.4 per 10,000 person-years, p = 0.04) [98]. The impact of bariatric surgery on self-injurious behavior is discussed in another section. (See 'Suicide' below.)

Other studies associated bariatric surgery with similar survival benefit [118,119].

FUNCTIONAL OUTCOMES — Besides weight loss and metabolic effects, bariatric surgery also improves functionality and quality of life of those who suffer from obesity-related comorbid conditions. The effect size, however, varies depending on the individual condition and the bariatric procedure performed.

Obstructive sleep apnea — Obesity is a known risk factor for obstructive sleep apnea (OSA). An increased prevalence of obstructive sleep apnea in patients with obesity is well established [120,121]. (See "Clinical presentation and diagnosis of obstructive sleep apnea in adults".)

Weight loss via behavioral modification improves overall health and decreases apnea hypopnea index (AHI; the number of apneas and hypopneas per hour of sleep). In addition, weight loss achieved from bariatric operations also reduces AHI and appears to be greater or similar to the efficacy of behavioral modification weight loss [122]. (See "Management of obstructive sleep apnea in adults", section on 'Weight loss and exercise'.)

As an example, a three-year follow-up study of the GATEWAY trial reported that RYGB resulted in greater weight loss (-10.6 versus +1.7 kg/m2 ) and greater reduction in AHI (-13.2 versus +5) compared with usual care [123]. Compared with the baseline, patients after RYGB were more likely to achieve remission of OSA (from 4.2 to 70.8 percent) and less likely to have persistent moderate (from 41.7 to 8.3 percent) or severe OSA (from 20.8 to 0 percent).

A meta-analysis of 69 studies performed in 2013 identified a high rate of remission or improvement in OSA following bariatric procedures. The meta-analysis included 3 randomized control trials, 11 prospective studies, and 55 case series containing 13,900 patients and found a comparable rate of remission or improvement of OSA for patients undergoing either Roux-en-Y gastric bypass (RYGB; n = 5340), adjustable gastric band (AGB; n = 4095), or sleeve gastrectomy (SG; n = 543) (79 versus 77 versus 86 percent, respectively) [124].

However, there are conflicting results on the benefits of bariatric surgery on OSA, in part because of varying selection criteria and lack of formal polysomnography outcome data in many of the studies [16,124-127]. A 2018 meta-analysis of randomized trials and nonrandomized before-and-after studies demonstrated that despite a reduction in AHI after bariatric surgery, OSA persisted at follow-up in the majority of patients [128]. The discrepancy was attributed to the non-uniform respiratory events scoring criteria used to derive the AHI by various studies.

Therefore, we suggest that patients undergoing bariatric surgery should be monitored long-term for possible residual OSA and treated accordingly, and that remission of OSA should be documented by a repeat sleep study prior to discontinuing continuous positive airway pressure (CPAP) in this patient population. (See "Management of obstructive sleep apnea in adults".)

Gastroesophageal reflux disease — Obesity is a well-established risk factor for the development of gastroesophageal reflux disease (GERD) [124,129-132]. (See "Pathophysiology of reflux esophagitis", section on 'Obesity'.)

The impact of bariatric surgery on development, remission, or exacerbation of GERD is an evolving topic of debate and is dependent upon the type of bariatric procedure performed:

RYGB — In general, RYGB is considered an effective antireflux procedure in patients with obesity. According to the American College of Surgeons Bariatric Surgery Center Network (ACS-BSCN) data, 70 percent of patients achieve symptom improvement or remission at one year following RYGB [61].

In a prospective study of 86 patients with body mass index (BMI) of 35 to 68 kg/m2 undergoing RYGB, fewer patients had GERD at six months after surgery than before surgery (33 versus 64 percent) [133]. In addition, there was also significant improvement in esophagitis, presence of extraesophageal syndromes, use of proton pump inhibitors, and decreased total acid exposure. Ten percent of patients developed de novo reflux symptoms postoperatively.

SG — The effect of SG on GERD is less clear, given that GERD improvement is less predictable and GERD may worsen or develop de novo [134-143]. Consequently, preoperative evaluation and counseling specific to GERD-related outcomes is recommended for all patients undergoing SG. For patients with Barrett's esophagus and uncontrolled severe GERD who require bariatric surgery, RYGB is a better surgical option than SG. (See "Laparoscopic sleeve gastrectomy".)

A retrospective review of the Bariatric Outcomes Longitudinal Database (BOLD) that included 4832 patients who had undergone SG found that most (84 percent) patients with preoperative GERD (n = 2150) continued to have postoperative symptoms [143]. Of the patients without preoperative GERD, 8.6 percent developed symptoms following an SG. The ACS-BSCN study found that 50 percent of patients with preoperative GERD undergoing an SG had remission or reduction of symptoms [61].

In a systematic review of 11 prospective and retrospective studies of SG that included 1058 patients, seven studies identified a decrease in GERD prevalence and four studies found an increase in GERD prevalence [140]. The 2011 International Sleeve Gastrectomy Expert Panel failed to reach a consensus regarding performance of SG in patients with gastric reflux [141]. The American Society for Metabolic and Bariatric Surgery position statement acknowledges the controversy but does not find GERD or Barrett's esophagus to be a contraindication to SG [144].

AGB — There are conflicting and inconclusive data on the association between AGB and postoperative GERD [61,142]. It appears that AGB may have antireflux properties for some patients, but the procedure may also be associated with the development or worsening of reflux symptoms in others.

A systematic review that included 20 studies and 3307 patients with obesity undergoing AGB found a decrease in prevalence of postoperative GERD compared with the prevalence of preoperative GERD (7.7 versus 32.9 percent) [142]. In addition, the rate of use of antireflux medications decreased in the AGB postoperative period (9.5 versus 27.5 percent), the prevalence of pathologic reflux also decreased in the postoperative period (29.4 versus 55.8 percent), and the lower esophageal pressures improved after AGB (16.9 versus 12.9 mmHg).

However, de novo reflux symptoms developed in the postoperative period in 15 percent of patients who were asymptomatic preoperatively, and the rate of esophageal dysmotility increased following AGB (12.6 versus 3.5 percent). The ACS-BSCN study found that 64 percent of patients with preoperative GERD undergoing an AGB had remission or reduction of symptoms [61].

Joint pain and physical activities — Severe obesity is associated with significant joint pain and limitation of physical function. Bariatric surgery is effective at achieving and maintaining weight loss, which may help reduce pain and improve physical function of the joints.

In an observational study, over 2000 participants were followed for three years after bariatric surgery (70 percent RYGB, 25 percent AGB, 5 percent other) [145]. At one year, between one-half and three-quarters of all participants reported significant improvements in body, hip, and knee pain as well as physical function, compared with their presurgical conditions. Between years 1 and 3, improvements were sustained in knee and hip pain but declined in body pain and physical function.

In retrospective and small prospective studies, musculoskeletal pain from osteoarthritis on weight-bearing joints improved in 73 percent of patients after successful bariatric surgery [146]. Bariatric surgery improves gait biomechanics and, in patients with severe obesity and osteoarthritis, improves pain and joint function [147].

On magnetic resonance (MR) imaging, the intravertebral disc height increased by almost 2 mm after surgery, indicating an improvement in inflammatory arthritis [148]. Additionally, proinflammatory cytokines such as interleukin-6 (IL-6) and C-reactive protein levels also decreased after bariatric surgery, indicating reprieve from a proinflammatory state due to the control of obesity [149]. As such, patients with obesity also noted decreased arthritis symptoms in non-weight-bearing joints such as wrists and fingers.

With reduced arthritis symptoms, Short Form-36 (SF-36) and other quality-of-life questionnaires noted significant improvement in patients' ability to move and exercise without pain after bariatric surgery [148,150,151]. A meta-analysis of 20 studies found self-reported physical activity began to improve within six months, and objectively measured physical activity improved after six months, and continued to for up to three years after bariatric surgery [152]. When measured objectively by accelerometry, however, a study found only a modest decrease in sedentary activity (5 percent) and a greater increase in moderate to vigorous intensity physical activity (38 percent) at one year after bariatric surgery [153]. There were no further improvement between years 1 and 3. The post-bariatric surgery level of physical activity still falls short of that recommended for general health and weight control.

Polycystic ovary syndrome — Polycystic ovarian syndrome (PCOS) is found in 30 to 70 percent of obese women of reproductive age and is associated with a high risk of infertility [154,155]. Weight reduction through diet and exercise and lifestyle modification can improve the hyperandrogenemic symptoms and insulin resistance associated with PCOS [156]. (See "Clinical manifestations of polycystic ovary syndrome in adults" and "Treatment of polycystic ovary syndrome in adults", section on 'Obesity'.)

Bariatric surgery is an alternative strategy for weight loss in women with PCOS. Based upon several small observational studies, obese women who effectively achieved weight loss following RYGB had restored menstrual cycles at approximately three to four months following the operation, marked lessening of hirsutism and hyperandrogenemia at eight months, and an increased ability to conceive within two years of surgery [157-159]. Insulin resistance was also ameliorated following RYGB. However, another study found that RYGB shortened the follicular phase and improved female sexual function without changing ovulation or clinical hyperandrogenism [160]. Only abstracts of case reports have been published for AGB and SG.

Obesity is a risk factor for infertility or subfertility in women in particular. The effect of bariatric surgery on female fertility and pregnancy is reviewed separately in a dedicated topic. (See "Fertility and pregnancy after bariatric surgery".)

Renal disorders — Chronic renal dysfunction in patients with obesity is usually secondary to the other comorbidities of obesity such as diabetes and hypertension. As those conditions improve after bariatric surgery, so does renal dysfunction [161]. In nonrandomized prospective studies, creatinine normalized within two years after RYGB in 76 percent of patients with abnormal preoperative levels [162]. Glomerular filtration rate (GFR) also improved within one year after bariatric surgery in each of the chronic kidney disease classes [163].

Urinary incontinence — Obesity is a strong, independent risk factor for urinary incontinence [164]. Obese persons may develop urinary incontinence from both increased intra-abdominal pressure [165] and weakened pelvic floor muscles [166].

In a large prospective cohort study, 1987 patients with obesity who underwent bariatric surgery were assessed preoperatively and at one and three years postoperatively for urinary incontinence [167]. Compared with preoperative baseline values, the prevalence of urinary incontinence decreased significantly at one and three years (from 49 to 18 and 25 percent in women, and from 22 to 10 and 12 percent in men). Weight loss, younger age, and the ability to ambulate were independently associated with remission of urinary incontinence. Thus, bariatric surgery may reduce urinary incontinence in patients with obesity.

Sexual health — In an observational cohort study (the Longitudinal Assessment of Bariatric Surgery [LABS]-2), approximately half of individuals who were not satisfied with their sexual life prior to bariatric surgery experienced improvements in satisfaction in five years of follow-up [168].

Nonalcoholic fatty liver disease — Nonalcoholic fatty liver disease (NAFLD) is one of the most common causes of chronic liver disease worldwide, and obesity is strongly associated with its development [169]. NAFLD is subdivided into nonalcoholic fatty liver (NAFL), hepatic steatosis without inflammation, and nonalcoholic steatohepatitis (NASH), which is associated with inflammation and can be indistinguishable histologically from alcoholic steatohepatitis. (See "Pathogenesis of nonalcoholic fatty liver disease" and "Epidemiology, clinical features, and diagnosis of nonalcoholic fatty liver disease in adults" and "Management of nonalcoholic fatty liver disease in adults", section on 'Weight loss'.)

The general approach to NAFLD or NASH in patients with obesity is lifestyle modification and weight loss [170]. If that fails, bariatric surgery is the best alternative option for weight reduction [171].

Bariatric surgery has been associated with decreased grade of hepatic steatosis and inflammation in patients with obesity and NAFLD [169,171-188]. The effect of bariatric surgery on hepatic fibrosis has been less consistently reported [169,171,188-192]. In the SPLENDOR study of 1158 patients with histologically confirmed NASH and obesity, bariatric surgery (gastric bypass or sleeve gastrectomy) was associated with a much lower 10 year cumulative incidence of major adverse liver outcomes (2.3 versus 9.6 percent) and major cardiovascular events (8.5 versus 15.7 percent) compared with nonsurgical management [193]. In a case-control study of close to 3000 patients with baseline NAFLD, bariatric surgery was associated with a decreased risk of developing cirrhosis at two years (hazard ratio 0.31, 95% CI 0.19-0.52) [187].

Although liver functional tests, specifically alanine aminotransferase (ALT), are widely used to screen for liver disease, they did not reliably exclude obesity-related liver disease (eg, NASH) in patients undergoing bariatric surgery, according to the LABS-1 and -2 studies [194]. Patients may benefit from needle biopsy of the liver at the time of bariatric surgery due to the inability of the preoperative liver function tests as well as surgeon inspection by laparoscopy to determine the extent of obesity-related hepatic histopathology [171].

Following bariatric surgery, patients should continue to have liver function tests monitored closely, given the potential for worsening liver fibrosis in some patients.

PSYCHOSOCIAL IMPACT — Obesity has been associated with psychological impairment [195]. Among patients seeking or undergoing bariatric surgery, the most common mental health conditions are depression (prevalence 19 percent) and binge eating disorder (17 percent); both estimates are higher than published rates for the general United States population [196].

Prospective studies and reviews report a general tendency for patients with psychopathologic disorders to improve or normalize after bariatric surgery [197-201]. This may occur because patients take an active role in changing their lives, even while they are still overweight [202,203]. However, there have been reports of an increase in mental health service presentations after bariatric surgery, particularly among those who had prior psychiatric illnesses or developed surgical complications requiring further surgery [204]. Additionally, increased incidences of self-injurious behaviors following bariatric surgery have also been reported [98,205].

Depression — Bariatric surgery has been associated with improvement in depression. This is best illustrated by a systematic review of 27 studies including over 50,000 patients [196]. Compared with before surgery, the prevalence and severity of depression were reduced by 8 to 74 percent (seven studies) and 40 to 70 percent (six studies), respectively, after surgery [196].

Eating disorders — In some studies, the prevalence and severity of eating disorders decreased after bariatric surgery [206-208]. As an example, in one retrospective study, the prevalence of picking/nibbling was lower following Roux-en-Y gastric bypass (RYGB) and laparoscopic adjustable gastric banding (LAGB), and the improvement was sustained across seven years of follow-up; the prevalence of loss-of-control eating and cravings also declined post-RYGB and remained lower through seven years [209]. However, in another study, following an initial decrease in the rate of binge eating disorder at two years (from 6.1 percent presurgery to 1.3 percent), there was an increase to 3.1 percent at three years [208]. In both studies, postsurgical loss of control/binge eating was associated with suboptimal weight loss.

Quality of life and body image — Several studies have shown postsurgical improvement in other aspects of psychosocial functioning, including a higher quality of life and more satisfaction with patients' own body image and appearance [210-212].

Suicide — Some patients experience psychosocial impairment following bariatric surgery [213]. Psychosocial impairment may lead to self-injurious behaviors. Two studies independently demonstrated an approximately 50 percent increase in the incidence of suicide after bariatric surgery. In one study, rates of suicide were higher in the surgery group than in the control group (2.7 versus 1.2 per 10,000 person-years) [98]. In another study, self-harm emergencies in 8815 patients who underwent bariatric surgery (mostly gastric bypass) increased from 2.33 to 3.63 per 1000 patient-years in a three-year period after surgery compared with before surgery [205].

The root cause for the increase in suicide incidence was not apparent from the studies. However, impaired psychosocial function may accompany lack of postoperative weight loss, and others may initially improve but later experience declines of function even with maintenance of weight loss [197,200,202,214]. Regardless, the results are consistent and call for enhanced screening of patients for self-harm behaviors after bariatric surgery.

Alcohol and other substance abuses — Increasing prevalence of alcohol and other substance abuses has been reported after bariatric surgery.

In the Longitudinal Assessment of Bariatric Surgery (LABS) study, the year 5 cumulative incidences of alcohol use disorder (AUD) symptoms, illicit drug use, and substance use disorder treatment were 20.8, 7.5, and 3.5 percent after RYGB and 11.3, 4.9 , and 0.9 percent after AGB [215].

In another multi-institutional study of AUD after bariatric surgery, the preoperative, one-year, and two-year postoperative prevalences of AUD were 7.6, 6.3, and 11.9 percent for RYGB, and 10.1, 9.0, and 14.4 percent for SG [216]. Most patients developed AUD following their second postoperative year.

HEALTH CARE FINANCIAL IMPACT — Financial impact of medical care is measured as cost effectiveness and cost savings [217]. While bariatric surgery may be more efficacious than medical or lifestyle intervention for long-term weight loss and remission of diabetes [48,51,53,56,57,218,219], short-term cost savings have been reported in some [220-222], but not all [223,224], studies, and long-term cost saving and cost effectiveness is strongly debated [217]. Bariatric operations in general are expensive, and the cost of inpatient care and complications may not be offset long term by the savings of improved health. Additionally, no one operation has been shown to be more cost effective than another.

A new economic model was developed to correct for methodology shortcomings in medical economic evaluations. For patients with moderate-to-severe obesity, this model identified surgical management as initially more costly than nonsurgical management but yielded improved outcomes based upon incremental cost-effectiveness ratios (ICER) [220].

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Bariatric surgery".)

SUMMARY AND RECOMMENDATIONS

Weight loss – All modern bariatric surgical procedures consistently achieve significant, sustained weight loss that is highly variable following each procedure. In general, biliopancreatic diversion (BPD) provides the most significant weight loss but also the most complications, sleeve gastrectomy (SG) and Roux-n-Y gastric bypass (RYGB) are quite similar in the amount of weight loss they induce, and adjustable gastric banding (AGB) produces slower and less predictable weight loss, because of which it is rarely performed. (See 'Weight loss' above.)

Type 2 diabetes – There is high-quality evidence that bariatric surgical procedures, including RYGB, SG, and BPD, plus medical therapy, are more effective against type 2 diabetes mellitus than medical therapy alone. Although there is some relapse with long-term follow-up, glycemic control achieved with bariatric surgery is generally durable. There is also evidence that bariatric surgery can reduce macro- and microvascular complications of diabetes. (See 'Efficacy' above and 'Durability' above and 'Diabetic complications' above.)

Metabolic syndrome – Metabolic syndrome is defined as the co-occurrence of metabolic risk factors for both type 2 diabetes and cardiovascular disease (abdominal obesity, hyperglycemia, dyslipidemia, and hypertension). The benefit of bariatric surgery on blood pressure control has been demonstrated in randomized trials and observational studies. Clinical studies also have demonstrated improved lipid profiles following bariatric procedures. As a result of resolved or improved cardiovascular risk factors such as diabetes, hypertension, and dyslipidemia, bariatric surgery is associated with reduced number of cardiovascular deaths and lower incidence of cardiovascular events in obese adults. (See 'Hypertension' above and 'Dyslipidemia' above and 'Cardiovascular risk' above.)

Cancer – In several large database studies, bariatric surgery has been associated with lower risks of developing postmenopausal breast cancer and endometrial, prostate, pancreatic, and colon cancer. The cancer mortality rate is also lower after bariatric surgery. The overall all-cause mortality appeared to be reduced after bariatric surgery compared with nonsurgical management of obesity but remains elevated compared with the general population. (See 'Cancer risk and mortality' above and 'Long-term survival' above.)

Functional outcomes – Although bariatric surgery also improves the functional outcomes and quality of life of those who suffer from obesity-related comorbid conditions, the data are less homogeneous, and the effect size varies depending on the individual condition and the bariatric procedure performed (see 'Functional outcomes' above):

Sleep apnea – Despite the fact that bariatric surgery decreases apnea hypopnea index (the number of apneas and hypopneas per hour of sleep) by inducing weight loss, some studies show that obstructive sleep apnea (OSA) persists. Thus, the remission of OSA should be documented by a repeat sleep study prior to discontinuing continuous positive airway pressure (CPAP) in this patient population. (See 'Obstructive sleep apnea' above.)

Gastroesophageal reflux disease – For patients with obesity and Barrett's esophagus or severe uncontrolled gastroesophageal reflux disease (GERD), RYGB is an effective antireflux procedure, whereas the effects AGB and SG have on existing and de novo GERD are less predictable. (See 'Gastroesophageal reflux disease' above.)

Arthritis – Weight loss achieved and maintained with bariatric surgery may help reduce pain and improve physical function of the joints. Both osteo- and some inflammatory arthritis appear to benefit. (See 'Joint pain and physical activities' above.)

Fatty liver disease - Bariatric surgery has been associated with decreased grade of steatosis, hepatic inflammation, and fibrosis in patients with obesity and nonalcoholic fatty liver disease (NAFLD). (See 'Nonalcoholic fatty liver disease' above.)

Psychologic illnesses – Bariatric surgery has been associated with improvement in depression, eating disorders, patient-perceived body image, and quality of life. However, the incidence of suicide as well as alcohol and other substance use have also been reported after bariatric surgery. (See 'Psychosocial impact' above.)

Variations between bariatric procedures – In most contemporary series, the efficacies of RYGB and SG are regarded as comparable, BPD is a complex procedure that requires specialized expertise, and AGB is less effective. We agree with the American Society for Metabolic and Bariatric Surgery (ASMBS) that the optimal choice of bariatric procedure (eg, RYGB, SG) is dependent upon individualized goals (eg, weight loss, glycemic control), available expertise (ie, surgeon, institution), patient preferences, and personalized risk assessment. (See 'RYGB and SG' above and 'Efficacy' above and 'Gastroesophageal reflux disease' above.)

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Topic 90469 Version 40.0

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