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Bariatric Surgery

  • Author: Alan A Saber, MD, MS, FACS; Chief Editor: John Geibel, MD, DSc, MSc, MA  more...
Updated: Jun 15, 2016


Obesity is a major health problem worldwide and has reached an epidemic proportion in the Western society. Evidence continues to accumulate that obesity is a major risk factor for many diseases and is associated with significant morbidity and mortality.

The most widely accepted measure of obesity is the body mass index (BMI). This number is calculated by dividing a patient's mass (kg) by his or her height (m2). A normal BMI is considered in the range of 18.5-24.9 kg/m2. A BMI of 25-29.9 kg/m2 is considered overweight. A BMI of 30 kg/m2 or greater is classified as obese; this classification is further subdivided into class I, II, or III obesity.

Considering other factors (eg, total muscle mass, waist circumference) besides the BMI may be important. For example, an extremely muscular individual may have an elevated BMI without being considered overweight. Waist circumference has been shown to be an excellent indicator of abdominal fat mass. A circumference of greater than 88 cm (35 in.) in women or greater than 102 cm (40 in.) in men strongly correlates with an increased risk of obesity-related disease.

Bariatric surgery is currently the only modality that provides a significant, sustained weight loss for morbidly obese patients, with resultant improvement in obesity-related comorbidities. A prospective, controlled Swedish study involving 4047 obese patients, half of whom had undergone bariatric procedures, followed up over 14.7 years, found that compared to usual care, bariatric surgery was associated with a significantly reduced number of cardiovascular deaths and a lower incidence of cardiovascular events in obese adults.[1]

In 1954, Kremen and Linner introduced jejunoileal bypass, the first effective surgery for obesity in the United States. In this procedure, the proximal jejunum was connected directly to the distal ileum, bypassing 90% of the small intestine out of the intestinal stream of ingested nutrients (blind loop). The procedure induced a state of malabsorption, which led to significant weight loss.

However, many patients developed complications secondary to malabsorption (eg, steatorrhea, diarrhea, vitamin deficiencies, oxalosis) or due to the toxic overgrowth of bacteria in the bypassed intestine (eg, liver failure, severe arthritis, skin problems). Consequently, many patients have required reversal of the procedure, and the procedure has been abandoned. This led to a search for better operations.

Modifications in the original procedures and the development of new techniques led to the following three basic concepts for bariatric surgery:

  • Gastric restriction (adjustable gastric banding, sleeve gastrectomy)
  • Gastric restriction with mild malabsorption (Roux-en-Y gastric bypass)
  • Combination of mild gastric restriction and malabsorption (duodenal switch)

In recent years, the field of bariatric surgery has been enriched by data from numerous clinical investigations and experience. The direction of future clinical investigations are proceeding in a number of directions, including the following:

  • Controlled, prospective, intervention studies
  • Establishment of a major prospective database to study bariatric surgery outcomes
  • Establishment of a pediatric (adolescent) bariatric surgery registry
  • Performance of randomized clinical trials to compare the safety and efficacy of different operative procedures
  • Controlled studies of new operative modalities (eg, gastric pacing) and nonoperative modalities of treatment
  • Study by meta-analysis of outcomes of comorbid conditions of morbid obesity
  • Study of the socioeconomic outcomes of bariatric surgery
  • Study by stratified risk assessment of the risk-to-benefit ratio of treating morbid obesity with bariatric surgery and without bariatric surgery

For patient education resources, see the Healthy Living Center, as well as Obesity and Surgery in the Treatment of Obesity.



Obesity occurs as the result of an imbalance between energy expenditure and caloric intake. This imbalance has been thought to be under genetic and environmental influence. The discovery of immunologic abnormalities in obesity that are related to the leptin-proopiomelanocortin system and elevated tumor necrosis factor alpha (TNF-α) brought a new perspective to the understanding of obesity.

Leptin (from Greek leptos, "thin") is a hormone made primarily in adipocytes. The circulating leptin levels reflect the amount of stored body fat. Leptin is a negative feedback signal that acts on the hypothalamus to alter the expression of several neuroendocrine peptides that regulate energy intake and expenditure. Central resistance to leptin is a prominent feature of obesity.

Increased leptin levels in individuals who are obese are independent of the lipid profile but strongly correlate with the BMI. Leptin exhibits direct effects on monocytes that results in secretion of the interleukin (IL)-1 receptor antagonist (IL-1RA). This cytokine antagonist has anti-inflammatory properties. Although leptin treatment works very well in patients who are leptin-deficient, the use of leptin in patients who are obese and who already have high levels of leptin has shown limited efficacy.



Obesity is a complex, multifactorial chronic disease influenced by the interaction of several factors, such as genetic, endocrine, metabolic, environmental (social and cultural), behavioral, and psychological components. The basic mechanism involves energy intake that exceeds energy output.



The number of overweight individuals in the world is estimated at 1.7 billion. In the United States, the problem is at epidemic proportions. As much as two thirds of the population in the United States is overweight, and half of the people in this group can be classified as obese.



The Swedish Obese Subjects (SOS) study is an ongoing, prospective study of 2010 obese participants who underwent bariatric surgery and 2037 obese patients who received usual care in the primary health care system. Compared to the control group, obese adults who underwent surgery experienced a reduced number of cardiovascular deaths and a lower incidence of heart attack and stroke.[2, 3]

Low back pain is a common complaint among obese patients. A retrospective study of morbidly obese patients who underwent bariatric surgery found that patients experienced a significant decrease in low back and radicular pain after surgery, which led to improvements in quality of life. Patients also experienced a marked increase in the L4-5 intervertebral disc height.[4]

An Australian study by Keating et al compared the results of weight-loss treatments in patients who had been diagnosed with type 2 diabetes mellitus in class I/II obesity, estimating the lifetime costs and quality-adjusted life-years (QALYs) for individuals who had undergone surgically induced weight loss and for patients who had utilized conventional weight loss treatment.[5]

In this study, the mean length of time for diabetes remission over a lifetime was 11.4 years in the surgical therapy group and 2.1 years in the conventional therapy group.[5] Over the remainder of their lifetime, patients in the surgical therapy group lived 15.7 discounted QALYs, compared with 14.5 discounted QALYs for patients in the conventional therapy group. For surgical and conventional therapy patients, the mean discounted lifetime costs were, respectively, Au $98,900 and Au $101,400 per patient (Au $1 = US $0.74). Compared with conventional therapy, surgically induced weight loss was associated with a mean healthcare saving of Au $2400 and with 1.2 additional QALYs per patient.

In another study, Keating et al  looked at the within-trial cost efficacy, over 2 years, of surgical treatment relative to that of conventional therapy for achieving remission in patients recently diagnosed with type 2 diabetes mellitus with class I/II obesity.[6]  Trial intervention costs included gastric banding surgery, mitigation of complications, outpatient medical consultations, medical investigations, pathology, weight-loss therapies, and medication.

An incremental cost-effectiveness analysis demonstrated that the mean 2-year intervention costs per patient were Au $13,400 for surgical therapy and Au $3400 for conventional therapy; laparoscopic adjustable gastric band (LAGB) surgery was responsible for 85% of the difference.[6] For surgical patients, outpatient medical consultation costs were threefold greater than those for conventional patients, but medication costs were 1.5 times higher for patients who underwent conventional therapy. The cost differences occurred primarily in the trial's first 6 months. In relation to conventional treatment, the incremental cost-effectiveness ratio for surgical therapy was Au $16,600 per case of diabetes remitted.

An updated Cochrane review from 2014 that included 22 trials with 1798 participants concluded that surgical treatment of obesity yielded greater improvement in weight loss and weight-associated comorbidities than nonsurgical interventions did, regardless of the type of procedure,[7]  though certain procedures were associated with greater weight loss and fewer comorbidities than others.

In this review, Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy had comparable outcomes, and both had better outcomes than adjustable gastric banding.[7]  In very-high-BMI patients, biliopancreatic diversion with duodenal switch yielded better weight loss than RYGB did. Outcomes were comparable for duodenojejunal bypass with sleeve gastrectomy and laparoscopic RYGB. Isolated sleeve gastrectomy led to better weight loss than adjustable gastric banding. Weight-related outcomes were similar for laparoscopic gastric imbrication and laparoscopic sleeve gastrectomy.

In general, with all 22 studies taken into account, rates of adverse events and reoperation were not well reported.[7]  Because the follow-up period in most of the trials reviewed was only 1 or 2 years, the long-term effects of bariatric surgery could not be definitively established.

Contributor Information and Disclosures

Alan A Saber, MD, MS, FACS FASMBS, Director of Bariatric and Metabolic Surgery, University Hospitals Case Medical Center; Surgical Director, Bariatric Surgery, Metabolic and Nutrition Center, University Hospitals Digestive Health Institute; Associate Professor of Surgery, Case Western Reserve University School of Medicine

Alan A Saber, MD, MS, FACS is a member of the following medical societies: American College of Surgeons, American Society for Metabolic and Bariatric Surgery, American Society for Gastrointestinal Endoscopy

Disclosure: Nothing to disclose.


Tarek H El-Ghazaly, MD Fellow of Minimally Invasive and Bariatric Surgery Research, Michigan State University, Kalamazoo Center for Medical Studies

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Chief Editor

John Geibel, MD, DSc, MSc, MA Vice Chair and Professor, Department of Surgery, Section of Gastrointestinal Medicine, and Department of Cellular and Molecular Physiology, Yale University School of Medicine; Director, Surgical Research, Department of Surgery, Yale-New Haven Hospital; American Gastroenterological Association Fellow

John Geibel, MD, DSc, MSc, MA is a member of the following medical societies: American Gastroenterological Association, American Physiological Society, American Society of Nephrology, Association for Academic Surgery, International Society of Nephrology, New York Academy of Sciences, Society for Surgery of the Alimentary Tract

Disclosure: Received royalty from AMGEN for consulting; Received ownership interest from Ardelyx for consulting.

Additional Contributors

Brian J Daley, MD, MBA, FACS, FCCP, CNSC Professor and Program Director, Department of Surgery, Chief, Division of Trauma and Critical Care, University of Tennessee Health Science Center College of Medicine

Brian J Daley, MD, MBA, FACS, FCCP, CNSC is a member of the following medical societies: American Association for the Surgery of Trauma, Eastern Association for the Surgery of Trauma, Southern Surgical Association, American College of Chest Physicians, American College of Surgeons, American Medical Association, Association for Academic Surgery, Association for Surgical Education, Shock Society, Society of Critical Care Medicine, Southeastern Surgical Congress, Tennessee Medical Association

Disclosure: Nothing to disclose.


We wish to thank Ollie J Jackson III, MD, Department of General Surgery, Michigan State University, Kalamazoo Center for Medical Studies, for previous contributions to this entry.

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Laparoscopic Roux-en-Y gastric bypass.
Adjustable gastric banding.
Sleeve gastrectomy.
Long Roux-en-Y gastric bypass.
Biliopancreatic diversion with duodenal switch.
Progression of surgical techniques, with open surgery in the first image and single-incision, transumbilical laparoscopic surgery in the third illustration.
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