Purpose of Gastric Bypass Surgery

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The purpose of gastric bypass surgery is to limit the amount of food you can eat and the number of calories your body can absorb. Not only can this help people with obesity lose weight, but it can also improve or cure obesity-related conditions, including diabetes, high blood pressure, and sleep apnea.

This article looks closely at the purpose of gastric bypass surgery, the criteria you must meet to be eligible for it, and the tests and labs to expect.

Verywell / Laura Porter

Diagnoses Related to Gastric Bypass Surgery

The primary goal of gastric bypass surgery is to lose weight in order to improve or reverse medical conditions associated with obesity.

Examples of such obesity-related conditions include:


There are certain criteria a patient must meet in order to be considered a candidate for a weight loss surgery like gastric bypass.

These criteria include a patient with:

BMI is a dated, flawed measure. It does not take into account factors such as body composition, ethnicity, sex, race, and age. 
Even though it is a biased measure, BMI is still widely used in the medical community because it’s an inexpensive and quick way to analyze a person’s potential health status and outcomes.

Due to a higher prevalence of abdominal (truncal) obesity, weight loss surgery may also be considered for Asian patients who have uncontrolled type 2 diabetes and a BMI as low as 27.5.

That said, meeting one of the above criteria is simply the first step in determining who is an appropriate candidate for surgery. Patients must be able to prove that they have been unsuccessful in maintaining a healthy weight through non-surgical means, such as lifestyle changes and drug treatments.

Coverage for Weight Loss Surgery

If you are considering gastric bypass surgery, be sure to check in with your insurance carrier to verify that you have met the requirements needed for the operation to be covered.

Tests and Labs

To confirm candidacy and to prepare for the outcome of the surgery, patients will need to undergo several evaluations with various healthcare professionals, usually beginning several weeks to months prior to the actual procedure date.

These healthcare professionals include:

  • A bariatric (weight loss) physician
  • A bariatric surgeon
  • A nutritionist or dietician
  • A psychologist or psychiatrist

The bariatric physician will review your medical history and order tests to either newly diagnose or monitor health conditions related to your obesity. Some of these conditions may need to be optimized prior to surgery in order to reduce the risk of surgical complications.

Examples of such tests include:

Your bariatric physician will also probably start you on a medical weight loss program, as losing some weight before surgery is typically recommended.

Your bariatric surgeon will review the pros and cons of the surgery with you and enroll you in a bariatric pre-operative education program. The purpose of this program is to learn about the nuances of the surgery, including what to expect in terms of the short and long-term recovery processes, as well as, the potential risks involved.

A nutritionist will prepare you for what your diet will look like after surgery. They will also help you adhere to a low-calorie liquid diet, which is often required beginning two to four weeks before surgery.

A psychologist or psychiatrist will discuss the mental and emotional stresses associated with the surgery and its aftermath. Since mental health conditions, especially depression and eating disorders, are associated with obesity, your mental health professional may also provide therapy or recommend/prescribe medication.

Finally, consultations with different specialists may also be needed before surgery. For example, women in their childbearing years undergoing gastric bypass may need to see an obstetrician to discuss birth control options after surgery.

This is because professional societies, like the American College of Obstetricians and Gynecologists (ACOG), recommend that women not become pregnant in the first 12 to 18 months after bariatric surgery.

A Word From Verywell

The possible benefits of undergoing gastric bypass surgery are vast. Besides improving (if not reversing) serious health problems, patients feel better about their appearance and often report having improved self-esteem and quality of life.

Still, undergoing this type of surgery is an incredibly big decision, one that requires deep consideration and thought. As you continue to educate yourself about gastric bypass or other weight-loss surgeries, do not hesitate to reach out to loved ones for support.

Also, remember to be kind to yourself during this long and arduous journey. A good piece of advice is to simply take one day at a day and remain focused on your ultimate goal of achieving a healthier life—something you truly deserve.

11 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  7. Lim RB. Bariatric operations for management of obesity: Indications and preoperative preparation.

  8. University of Pittsburgh. Preparing for bariatric surgery.

  9. Edholm D, Kullberg J, Karlsson FA, Haenni A, Ahlström H, Sundbom M. Changes in liver volume and body composition during 4 weeks of low calorie diet before laparoscopic gastric bypassSurg Obes Relat Dis. 2015;11(3):602-6. doi:10.1016/j.soard.2014.07.018

  10. Luppino FS et al. Overweight, obesity, and depression: a systematic review and meta-analysis of longitudinal studies. Arch Gen Psychiatry. 2010;67(3):220-9. doi:10.1001/archgenpsychiatry.2010.2

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Additional Reading

By Colleen Doherty, MD
 Colleen Doherty, MD, is a board-certified internist living with multiple sclerosis.