Bariatric Surgery


Bariatric surgery is a surgical weight-loss procedure that reduces or bypasses the stomach or small intestine so that severely overweight people can achieve significant and permanent weight loss.


Bariatric surgery is performed only on teens and adults who are severely obese with a body mass index (BMI) above 40 and those with a BMI between 35 and 40 who have health problems related to obesity such as type 2 diabetes, sleep apnea, high blood pressure, or heart disease. This level of obesity can result in many serious and potentially deadly health problems. Surgery is performed on people whose risk of surgery complications is outweighed by the need to lose weight to prevent health complications and for whom supervised weight-loss and exercise programs have repeatedly failed. Obesity surgery, however, does not make people thin. Most people lose about 60% of their excess weight through gastric bypass surgery and 40% with sleeve gastrectomy. Changes in diet and exercise are required to maintain a normal weight.

The theory behind obesity surgery is that if the volume the stomach holds is reduced and the entrance into the intestine is made smaller to slow stomach emptying, or part of the small intestine is bypassed or shortened, people will not be able to consume and/or absorb as many calories. With obesity surgery the volume of food the stomach can hold is reduced from about four cups to about a half cup.

Insurers may consider obesity surgery elective surgery and not cover it under their policies. Documentation of the necessity for surgery and approval from the insurer should be sought before this operation is performed.


Many people lose about 60% of the weight they need to reach their ideal weight through obesity surgery. However, surgery is not a magic weight-loss operation, and success also depends on the patient's willingness to exercise and eat low-calorie foods. A 2014 report showed that gastric bypass and sleeve gastrectomy had similar weight loss results and that both procedures had better outcomes than adjustable gastric banding. A 2015 study found bariatric surgeries were associated with dramatic weight loss that was sustained for at least four years after surgery. Along with weight loss, patients experienced substantial improvement in pre-existing type 2 diabetes and high blood pressure as well as reduced risks of subsequent type 2 diabetes, high blood pressure, heart attack, and obstructive sleep apnea.

Obesity surgery is usually performed in a hospital by a surgeon who has experience with obesity surgery or at a center that specializes in the procedure. Most are performed laparoscopically, require general anesthesia, and may take several hours.

Three procedures are typically used for obesity surgery:

In this Roux-en-Y gastric bypass, the stomach is separated into two sections. Food is bypassed from the larger stomach to the smaller stomach.

In this Roux-en-Y gastric bypass, the stomach is separated into two sections. Food is bypassed from the larger stomach to the smaller stomach.
(Illustration by PreMediaGlobal. Cengage Learning.)


Obesity surgery is not appropriate for people who have substance addictions or who have psychological disorders. Other considerations in choosing candidates for obesity surgery include the general health of the person and willingness to comply with follow-up treatment.


After patients are carefully selected as appropriate for obesity surgery, they receive standard preoperative blood and urine tests and meet with an anesthesiologist to discuss how their health may affect the administration of anesthesia. Pre-surgery counseling is done to help patients anticipate what to expect after the operation. Before surgery, patients may be told to start a program of physical activity and to stop any tobacco use. It is also recommended that patients follow a very low-calorie diet before the procedure to reduce surgical risks. Interestingly, patients who consumed a very low-calorie liquid diet lost significantly more weight and visceral body fat than those who ate the same calories with normal foods, according to one study published in 2015.


After the operation, patients cannot eat for one to two days. Then they follow a twelve-week diet beginning with liquids only, then ground-up or soft foods, and then regular foods. Patients are expected to work on changing their eating and exercise habits to assist in weight loss. Most people eat three to four small meals a day once they return to solid food. Bariatric surgery changes how the body handles food, and it becomes more difficult to absorb certain nutrients including iron, vitamin B12, folate, calcium, and vitamin D.

Body mass index (BMI)—
A scale that expresses a person's weight in relation to height.
High blood pressure—
A blood pressure reading of 140/90 or higher.
Abnormally high levels of lipids (fats) in the blood.
Having a body mass index (BMI) of 30 or more, meaning one has too much body fat.
Obstructive sleep apnea—
A potentially serious sleep disorder that causes breathing to stop and start repeatedly during sleep.
Type 2 diabetes—
Formerly called adult-onset diabetes. In this form of diabetes, the pancreas either does not make enough insulin or cells become insulin resistant and do not use insulin efficiently.

Eating too quickly or too much after obesity surgery can cause nausea and vomiting as well as intestinal “dumping,” a condition in which undigested food is shunted too quickly into the small intestine, causing pain, diarrhea, weakness, and dizziness.


As in any abdominal surgery, there is always a risk of excessive bleeding, infection, and allergic reaction to anesthesia. Specific risks associated with obesity surgery include leaking or stretching of the pouch and loosening of the gastric staples. About 10% of people experience minor complications including constipation, dumping syndrome (nausea, vomiting, and weakness caused by eating high-sugar meals), gallstones, and wound infections. Less than 5% have serious complications such as bleeding in the stool, blood clots to the lungs, abdominal pain, and weakness from leaks. Although the average death rate associated with this procedure is less than 1%, the rate varies from center to center, ranging from 0.2%–0.5%. Long-term failure rates can reach 50%, sometimes making additional surgery necessary.

Parental concerns

Bariatric surgery may be performed on adolescents with type 2 diabetes because type 2 diabetes is associated with an increased risk of hypertension, abnormal amount of lipids in the blood, and nonalcoholic fatty liver disease. Studies indicate that diabetes in teens can go into complete remission after Roux-en-Y gastric bypass (RYGB). The other type of surgery done on adolescents is adjustable gastric band (AGB). Surgery may also help the adolescent's emotional and social health.


See also Body mass index ; Diabetes mellitus ; Fats ; Hyperlipidemia ; Hypertension ; Liquid diets ; Obesity ; Optifast .



Cook, Colleen. The Success Habits of Weight-Loss Surgery Patients. 3rd ed. Salt Lake City, UT: Bariatric Support Centers International, 2012.

Levine, Patt, and Michele Bontempo-Saray. Eating Well After Weight Loss Surgery: Over 140 Delicious Low-Fat High-Protein Recipes to Enjoy the Weeks, Months, and Years after Surgery. New York: Marlowe & Co., 2004.

Radcliffe, Jennifer. Cut Down to Size: Achieving Success with Weight Loss Surgery. 3rd ed. New York: Routledge, 2013.


Campos, G. M., C. Rabl, G. R. Roll, et al. “Better Weight Loss, Resolution of Diabetes, and Quality of Life for Laparoscopic Gastric Bypass vs Banding: Results of a 2-Cohort Pair-Matched Study.” Archives of Surgery 146, no. 2 (February 2011): 149–55.

Colquitt, Jill L., Karen Pickett, Emma Loveman, et al. “Surgery for Weight Loss in Adults.” Cochrane Database of Systematic Reviews 8 (August 8, 2014). (accessed April 12, 2018).

Douglas, Ian J., Krishnan Bhaskaran, Rachel L. Batterham, et al. “Bariatric Surgery in the United Kingdom: A Cohort Study of Weight Loss and Clinical Outcomes in Routine Clinical Care.” PLoS Medicine 12, no. 12 (December 22, 2015). (accessed April 12, 2018).

Faria, Silvia Leite, Orlando Pereira Faria, Mariane de Almeida Cardeal, et al. “Effects of a Very Low Calorie Diet in the Preoperative Stage of Bariatric Surgery: A Randomized Trial” Surgery for Obesity and Related Diseases 11, no.1 (January/February 2015): 230–7.

Gerber, P., C. Anderin, and A. Thorell. “Weight Loss Prior to Bariatric Surgery: An Updated Review of the Literature” Scandinavian Journal of Surgery 104, no. 1 (March 2014): 33–9.

Laurenius, A., I. Larsson, M. Bueter, et al. “Changes in Eating Behaviour and Meal Pattern Following Roux-en-Y Gastric Bypass.” International Journal of Obesity 36, no. 3 (March 2012): 348–55.

Thakkar, R. K., and M. P. Michalsky. “Update on Bariatric Surgery in Adolescence.” Current Opinion in Pediatrics 27, no. 3 (June 2015): 370–6.


Consumer Guide to Bariatric Surgery. “What You Need to Know about Weight Loss Surgery.” Ceatus Media Group. (accessed April 12, 2018).

Mayo Clinic staff. “Bariatric Surgery.” Mayo Clinic. (accessed April 12, 2018).

National Institute of Diabetes, Digestive and Kidney Diseases. “Bariatric Surgery.” National Institutes of Health. (accessed April 12, 2018).

WebMD. “Gastric Bypass Surgery Directory.” . (accessed April 12, 2018).

Saber, Alan A. “Bariatric Surgery.” Medscape. (accessed April 12, 2018).


American Society for Metabolic and Bariatric Surgery, 100 SW 75th St., Ste. 201, Gainesville, FL, 32607, (352) 331-4900, Fax: (352) 331-4975,, .

Obesity Medicine Association, 101 University Blvd., Ste. 330, Denver, CO, 80206, (303) 770-2526, Fax: (303) 779-4834,, .

Tish Davidson, AM
Revised by Jeanie Simoncic

  This information is not a tool for self-diagnosis or a substitute for professional care.