Gastric Bypass Surgery for Weight Loss

Dr. Donn Spight smiling and standing in an interesting building interior

Dr. Donn Spight is an expert in minimally invasive laparoscopic surgeries, including gastric bypass. He is also a co-author of a 2018 textbook for laparoscopic surgeons.

At OHSU, you’ll receive care from a team that does dozens of gastric bypass surgeries each year. You’ll also find:

  • Surgeons with advanced training in minimally invasive gastric bypass surgery.
  • A full team of experts, including dietitians and psychologists, to help you reach your goals.
  • High rates of success in losing weight and improving health. 

What is gastric bypass surgery?

Your surgeon separates the top part of your stomach to create a pouch about the size of a small egg. The surgeon attaches the pouch to your small intestine. This bypasses most of your stomach and upper intestine. 

The procedure, also known as a Roux-en-Y gastric bypass, is almost always done with a minimally invasive laparoscope. This fiber-optic instrument requires only small incisions.

Gastric Bypass Surgery

roux en y picture

How does gastric bypass work?

Your appetite will fall because the smaller pouch means you feel full after small meals. Your body will absorb fewer calories and nutrients. Your stomach will also send different signals to the brain and gastrointestinal system, leading to metabolism changes that can reduce appetite.

Gastric bypass generally results in higher weight loss than other treatments, though gastric sleeve results are close.

What to expect

This information is for the vast majority of patients who have laparoscopic surgery. About 99 percent are done this way at OHSU.

Hospital stay: You will probably spend one or two nights in the hospital.


  • Most patients can walk three to four hours after surgery.
  • Most can resume daily tasks such as showering almost immediately.
  • You should be able to fix meals and do other small tasks as soon as you get home. Then you can slowly ramp up activity over the next few weeks. Learn more about Life After Surgery.

Diet: You will have liquids for the first two weeks before slowly adding solid foods in stages. It may be two months before you settle into a long-term diet.

Weight loss: More than 85 percent of patients lose at least half their excess weight and keep it off for years, according to an expansive National Institutes of Health report. OHSU produces similar results.


  • Gastric bypass can be slightly more effective than gastric sleeve in achieving weight loss.
  • It does not require a foreign object in the body, as gastric banding does.
  • It can be an effective long-term treatment for Type 2 diabetes and acid reflux disease.
  • Patients who have bariatric surgery, including gastric bypass, have higher life expectancy, better health and higher quality of life than similar people who don’t.

Risks and potential side effects

At OHSU, only about one in 200 gastric bypass patients is readmitted for treatment of a major complication. Still, every surgery carries some risk.

  • Gastric bypass is more complex than other bariatric surgeries, so more short-term complications are possible. These include leaking from intestinal connections, blood clots, bleeding, pneumonia and infections.
  • A few patients develop dumping syndrome, when food moves too quickly through the digestive system. This can lead to nausea, vomiting and diarrhea but usually goes away within a few months. This condition is also less common than many patients fear.
  • Long-term complications may include hernias, ulcers and narrowing of the intestinal connections.
  • Gastric bypass can cause vitamin and mineral deficiencies. Patients must take supplements and follow dietary recommendations for the rest of their lives.
  • The surgery typically is not reversible.
  • You can't use nonsteroidal anti-inflammatory drugs (NSAIDs) or nicotine products after this surgery because they raise the risk of ulcers.

Is gastric bypass right for me?

See our Considering Bariatric Surgery page to learn more about how patients are assessed.

Gastric bypass may be recommended if:

  • You have a high weight-loss goal. Gastric bypass typically results in slightly more weight loss than gastric sleeve.
  • You have Type 2 diabetes or acid reflux disease. Gastric bypass has proved effective in improving these conditions in many patients.