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Bariatric Surgery


Adrienne Youdim

, MD, David Geffen School of Medicine at UCLA

Last review/revision Aug 2021 | Modified Sep 2022
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Bariatric surgery is the surgical alteration of the stomach, intestine, or both to cause weight loss.

In the US, about 250,000 bariatric operations are done in each year. Development of safer laparoscopic approaches has made this surgery more popular.

Indications for Bariatric Surgery

To qualify for bariatric surgery, patients should

Bariatric surgery should also be considered for patients with a BMI of 30 to 34.9 with type 2 diabetes who have inadequate glycemic control despite optimal lifestyle and medical therapy (1 Indications reference Bariatric surgery is the surgical alteration of the stomach, intestine, or both to cause weight loss. In the US, about 250,000 bariatric operations are done in each year. Development of safer... read more ).

Contraindications include

  • An uncontrolled psychiatric disorder such as major depression

  • Current drug or alcohol abuse

  • Cancer that is not in remission

  • Another life-threatening disorder

  • Inability to comply with nutritional requirements, including life-long vitamin replacement (when indicated)

Indications reference

  • 1. Mechanick JI, Apovian C, Brethauer S, et al: Clinical practice guidelines for the perioperative nutrition, metabolic, and nonsurgical support of patients undergoing bariatric procedures - 2019 update: cosponsored by American Association of Clinical Endocrinologists/American College of Endocrinology, The Obesity Society, American Society for Metabolic & Bariatric Surgery, Obesity Medicine Association, and American Society of Anesthesiologists. Surg Obes Relat Dis 16(2):175-247, 2020. doi: 10.1016/j.soard.2019.10.025

Procedures for Bariatric Surgery

The most common procedures done in the US include

Most procedures are done laparoscopically, resulting in less pain and a shorter healing time than open surgery. Traditionally, bariatric surgery has been classified as restrictive and/or malabsorptive, referring to the presumptive mechanism of weight loss. However, other factors appear to contribute to weight loss; for example, RYGB (traditionally classified as malabsorptive) and sleeve gastrectomy (traditionally classified as restrictive) both result in metabolic or hormonal changes that favor satiety and weight loss and in other hormonal changes (eg, an increase in insulin release [incretin effect]) that appear to contribute to the rapid remission of diabetes Diabetes Mellitus (DM) Diabetes mellitus is impaired insulin secretion and variable degrees of peripheral insulin resistance leading to hyperglycemia. Early symptoms are related to hyperglycemia and include polydipsia... read more .

After RYGB (particularly) or sleeve gastrectomy, levels of gastrointestinal hormones, such as glucagon-like peptide-1 (GLP-1) and peptide YY (PYY), are increased, possibly contributing to satiety, weight loss, and remission of diabetes. Increased insulin sensitivity is evident immediately postoperatively, before significant weight loss occurs, suggesting that neurohormonal factors are prominent in remission of diabetes. A change in gut microbiome may also contribute to changes in weight after RYGB. Bariatric surgery reduces mortality caused by cardiovascular diseases, diabetes, and cancer.

Roux-en-Y gastric bypass (RYGB) surgery

RYGB is usually done laparoscopically. A small part of the proximal stomach is detached from the rest, creating a stomach pouch of < 30 mL. Also, food bypasses part of the stomach and small intestine, where it is normally absorbed, reducing the amount of food and calories absorbed. The pouch is connected to the proximal jejunum; the opening between them is narrow, limiting the rate of gastric emptying. The segment of small intestine connected to the bypassed stomach is attached to the distal small intestine. This arrangement allows bile acids and pancreatic enzymes to mix with gastrointestinal contents, limiting malabsorption and nutritional deficiencies.

For many patients who have had RYGB, eating high-fat and high-sugar foods can cause dumping syndrome; symptoms can include light-headedness, diaphoresis, nausea, abdominal pain, and diarrhea. Dumping syndrome may inhibit the consumption of such foods by adverse conditioning.

Roux-en-Y gastric bypass surgery

Roux-en-Y gastric bypass surgery

Sleeve gastrectomy

In the past, sleeve gastrectomy was done only when patients are considered too high risk for procedures such as RYGB and biliopancreatic diversion (eg, patients with a BMI > 60), typically before one of these procedures or another similar procedure is done. However, because sleeve gastrectomy causes substantial and sustained weight loss, it is being used in the US as definitive treatment for severe obesity. Part of the stomach is removed, creating a tubular stomach passage. The procedure does not involve anatomic changes to the small intestine.

Mean excess weight loss tends to be higher than with that with adjustable gastric banding. Although sleeve gastrectomy is traditionally classified as a restrictive procedure, weight loss is probably also related to neurohormonal changes.

The most serious complication is gastric leak at the suture line; it occurs in 1 to 3% of patients.

Adjustable gastric banding

Use of adjustable gastric banding has dramatically decreased in the US. A band is placed around the upper part of the stomach to divide the stomach into a small upper pouch and a larger lower pouch. Typically, the band is adjusted 4 to 6 times by injecting saline into the band via a port that is placed subcutaneously. When saline is injected, the band expands, restricting the upper pouch of the stomach. As a result, the pouch can hold much less food, patients eat more slowly, and satiety occurs earlier. This procedure is usually done laparoscopically. Saline can be removed from the band if a complication occurs or if the band is overly restrictive.

Weight loss with the band varies and is related to the frequency of follow-up; more frequent follow-ups result in greater weight loss. Although postoperative morbidity and mortality are less than those with RYGB, long-term complications, including repeat operations, are more likely, possibly occurring in up to 15% of patients.

Adjustable gastric banding

Adjustable gastric banding

Biliopancreatic diversion with a duodenal switch

This procedure accounts for < 5% of bariatric procedures done in the US.

Part of the stomach is removed, causing restriction. The remaining part empties into the duodenum. The duodenum is cut and attached to the ileum, bypassing much of the small intestine, including the sphincter of Oddi (where bile acids and pancreatic enzymes enter); as a result, food absorption decreases. This procedure is technically demanding but can sometimes be done laparoscopically.

Malabsorption and nutritional deficiencies often develop.

Vertical banded gastroplasty

Vertical banded gastroplasty is no longer commonly done because complication rates are high and the resulting weight loss is insufficient. For this procedure, a stapler is used to divide the stomach into a small upper pouch and a larger lower pouch. A nonexpandable plastic band is placed around the opening where the upper pouch empties into the lower pouch.

Procedures reference

Preoperative Evaluation for Bariatric Surgery

Preoperative evaluation consists of

  • Diagnosis and correction of comorbid conditions as much as possible

  • Assessment of readiness and ability to engage in lifestyle modification

  • Exclusion of contraindications to surgery

  • Review of the postoperative diet and assessment of the patient's ability to make necessary lifestyle changes by a dietitian

  • Identification of any uncontrolled psychiatric disorder and any dependencies that would preclude surgery and identification and discussion of potential obstacles to adherence to lifestyle changes postoperatively by a psychologist or other qualified mental health care practitioner

Extensive preoperative evaluation is not routinely necessary, but preoperative testing may be necessary based on clinical findings, and measures to control certain conditions (eg, hypertension) or reduce risk may be taken.

Risks of Bariatric Surgery

Perioperative risks are lowest when bariatric surgery is done in an accredited center.

Complications include

These complications can cause significant morbidity, prolong hospitalization, and increase costs. Tachycardia may be the only early sign of anastomotic leak.

Nutritional deficiencies (eg, protein-energy undernutrition Protein-Energy Undernutrition (PEU) Protein-energy undernutrition (PEU), previously called protein-energy malnutrition, is an energy deficit due to deficiency of all macronutrients. It commonly includes deficiencies of many micronutrients... read more , vitamin B12 deficiency Vitamin B12 Deficiency Dietary vitamin B12 deficiency usually results from inadequate absorption, but deficiency can develop in vegans who do not take vitamin supplements. Deficiency causes megaloblastic anemia, damage... read more , iron deficiency Iron Deficiency Iron (Fe) is a component of hemoglobin, myoglobin, and many enzymes in the body. Heme iron is contained mainly in animal products. It is absorbed much better than nonheme iron (eg, in plants... read more ) may result from inadequate intake, inadequate supplementation, or malabsorption. Malodorous flatulence, diarrhea, or both may develop, particularly after malabsorptive procedures. Calcium and vitamin D absorption may be impaired, causing deficiencies and sometimes hypocalcemia Hypercalcemia Hypercalcemia is a total serum calcium concentration > 10.4 mg/dL (> 2.60 mmol/L) or ionized serum calcium > 5.2 mg/dL (> 1.30 mmol/L). Principal causes include hyperparathyroidism... read more and secondary hyperparathyroidism. With prolonged vomiting, thiamin deficiency Thiamin Deficiency Thiamin deficiency (causing beriberi) is most common among people subsisting on white rice or highly refined carbohydrates in countries with high rates of food insecurity and among people with... read more may occur.

Incidence of psychologic disorders such as depression Depressive Disorders Depressive disorders are characterized by sadness severe enough or persistent enough to interfere with function and often by decreased interest or pleasure in activities. Exact cause is unknown... read more is increased in patients having bariatric surgery. A 2016 meta-analysis confirmed this increase in preoperative depression and reported a postoperative decrease in the prevalence and severity of depression (1 Risks references Bariatric surgery is the surgical alteration of the stomach, intestine, or both to cause weight loss. In the US, about 250,000 bariatric operations are done in each year. Development of safer... read more ). One large study suggested that the risk of suicide in patients who had bariatric surgery was increased compared with that in controls (2.7 versus 1.2 per 10,000 person-year; hazard ratio 1.71 [0.69 to 4.25]; P value = 0.25 [ 2 Risks references Bariatric surgery is the surgical alteration of the stomach, intestine, or both to cause weight loss. In the US, about 250,000 bariatric operations are done in each year. Development of safer... read more ]). Incidence of alcohol use disorder Alcohol Use Disorder and Rehabilitation Alcohol use disorder involves a pattern of alcohol use that typically includes craving and manifestations of tolerance and/or withdrawal along with adverse psychosocial consequences. Alcoholism... read more also appears to be increased after bariatric surgery (3 Risks references Bariatric surgery is the surgical alteration of the stomach, intestine, or both to cause weight loss. In the US, about 250,000 bariatric operations are done in each year. Development of safer... read more ).

Eating habits may be disordered. Adjusting to new eating habits can be difficult.

Risks references

Prognosis for Bariatric Surgery

In hospitals accredited by the American Society of Bariatric Surgery as centers of excellence (COE), overall 30-day mortality is 0.2 to 0.3%. However, some data indicate that lower rates of serious complications are predicted more accurately by the number of procedures done in the hospital and by the surgeon than by COE status.

Average excess weight loss depends on the procedure.

For laparoscopic adjustable gastric banding, weight loss is

  • 45 to 72% at 3 to 6 years

  • 14 to 60% at 7 to 10 years

  • About 47% at 15 years

Percentage of weight loss is related to the frequency of follow-ups and number of band adjustments. Patients with a lower BMI tend to lose more excess weight than those with a higher BMI.

For sleeve gastrectomy, weight loss is

  • 33 to 58% at 2 years

  • 58 to 72% at 3 to 6 years

Longer-term data are not available.

For Roux-en-Y gastric bypass, weight loss is

  • 50 to 65% after 2 years

Weight loss after RYGB is maintained for up to 10 years.

Follow-up after Bariatric Surgery

Regular, long-term follow-up after bariatric surgery helps ensure adequate weight loss and prevent complications. After Roux-en-Y gastric bypass or sleeve gastrectomy, patients should be monitored every 4 to 12 weeks during the period of rapid weight loss (usually about the first 6 months after surgery), then every 6 to 12 months thereafter. With laparoscopic adjustable gastric banding, results appear to be optimal when patients are monitored and the band is adjusted at least 6 times during the first year after surgery.

Weight and blood pressure are checked, and eating habits are reviewed. Blood tests (usually complete blood count, electrolytes, glucose, blood urea nitrogen, creatinine, albumin, and protein and liver tests) are done at regular intervals. Glycosylated Hb (HbA1c) and fasting lipid levels should be monitored if they were abnormal before surgery. Depending on the type of procedure, vitamin and mineral levels, including calcium, vitamin D, vitamin B12, folate, iron, and thiamin (vitamin B1), may need to be monitored. Because secondary hyperparathyroidism is a risk, parathyroid hormone levels should also be monitored. Bone density should be measured after sleeve gastrectomy or Roux-en-Y gastric bypass.

Clinicians should check for any changes in response to antihypertensives, insulin, oral hypoglycemics, or lipid-lowering drugs during the period of rapid weight loss after surgery.

To minimize risk of hypoglycemia Hypoglycemia Hypoglycemia, or low plasma glucose level can result in sympathetic nervous system stimulation, and central nervous system dysfunction. In patients with diabetes who take insulin or antihyperglycemic... read more (due to increased insulin sensitivity after bariatric surgery) in patients with diabetes, clinicians should adjust the dose of insulin and decrease the dose of oral hypoglycemics (particularly sulfonylureas) or stop them after Roux-en-Y gastric bypass or sleeve gastrectomy.

Key Points

  • Consider weight loss surgery if patients are motivated, have not succeeded using nonsurgical treatments, and have a BMI of > 40 kg/m2 or a BMI of > 35 kg/m2 plus a serious complication (eg, diabetes, hypertension, obstructive sleep apnea, high-risk lipid profile) or a BMI of 30 to 34.9 with type 2 diabetes and inadequate glycemic control despite optimal lifestyle and medical therapy.

  • Weight loss surgery is contraindicated if patients have an uncontrolled psychiatric disorder (eg, major depression), drug or alcohol abuse, cancer that is not in remission, or another life-threatening disorder or if they cannot comply with nutritional requirements (including life-long vitamin replacement when indicated).

  • The most common procedures are sleeve gastrectomy and Roux-en-Y gastric bypass; use of adjustable gastric banding has decreased dramatically in the US.

  • Monitor patients regularly after surgery for maintenance of weight loss, resolution of weight-related comorbid disorders, and complications of surgery (eg, nutritional deficiencies, metabolic bone disease, gout, cholelithiasis, nephrolithiasis, depression, alcohol abuse).

Drugs Mentioned In This Article

Drug Name Select Trade
Calcidol, Calciferol, D3 Vitamin, DECARA, Deltalin, Dialyvite Vitamin D, Dialyvite Vitamin D3, Drisdol, D-Vita, Enfamil D-Vi-Sol, Ergo D, Fiber with Vitamin D3 Gummies Gluten-Free, Happy Sunshine Vitamin D3, MAXIMUM D3, PureMark Naturals Vitamin D, Replesta, Replesta Children's, Super Happy SUNSHINE Vitamin D3, Thera-D 2000, Thera-D 4000, Thera-D Rapid Repletion, THERA-D SPORT, UpSpring Baby Vitamin D, UpSpring Baby Vitamin D3
Aluvea , BP-50% Urea , BP-K50, Carmol, CEM-Urea, Cerovel, DermacinRx Urea, Epimide-50, Gord Urea, Gordons Urea, Hydro 35 , Hydro 40, Kerafoam, Kerafoam 42, Keralac, Keralac Nailstik, Keratol, Keratol Plus, Kerol, Kerol AD, Kerol ZX, Latrix, Mectalyte, Nutraplus, RE Urea 40, RE Urea 50 , Rea Lo, Remeven, RE-U40, RYNODERM , U40, U-Kera, Ultra Mide 25, Ultralytic-2, Umecta, Umecta Nail Film, URALISS, Uramaxin , Uramaxin GT, Urea, Ureacin-10, Ureacin-20, Urealac , Ureaphil, Uredeb, URE-K , Uremez-40, Ure-Na, Uresol, Utopic, Vanamide, Xurea, X-VIATE
Albuked , Albumarc, Albuminar, Albuminex, AlbuRx , Albutein, Buminate, Flexbumin, Kedbumin, Macrotec, Plasbumin, Plasbumin-20
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