Gastric bypass surgery

What is gastric bypass?

Gastric bypass is the most commonly performed type of bariatric surgery in the United States. It involves creating a small stomach pouch and attaching it to the middle of the small intestine, bypassing part of the intestine. Like other metabolic surgeries, it changes the amount of food your body can digest, and changes the signals that travel between your digestive system and your brain.

How does gastric bypass work?

  1. A small stomach pouch is created, and the rest of the stomach is removed.
  2. The small intestine is rerouted to connect to the pouch.
  3. The old stomach is connected to small intestine lower down, allowing the bile and pancreatic fluids to help fully digest food. 

The food passes through the smaller-sized pouch directly into the small intestines, but the acids and enzymes from the old stomach and upper small intestine can still aid digestion. It works in several ways:

  • Smaller pouch leads to smaller meals (fewer calories being absorbed)
  • Bypassed small intestine portion absorbs fewer calories and nutrients
  • Hormonal signals between the stomach and the brain are changed
  • Typical outcomes include weight loss, improvement in metabolic syndrome, and overall health and wellbeing

What are the health benefits of gastric bypass?

  • Clinical studies show that patients experience a variety of benefits after surgery
    • An average of 62% excess weight loss(15)
    • Significant improvements in type 2 diabetes (68%), high blood pressure (66%), sleep apnea (76%), and high cholesterol (95%)(1, 16, 17)
    • Increased physical activity, productivity, wellbeing, economic opportunities, and self-confidence(11) 
    • Significant weight loss was retained for 14 years(18)
    • Minimally invasive procedure leads to shorter hospital stays and recovery time
  • Several patients saw improved or resolved health conditions after the gastric bypass surgery:
    • Type 2 diabetes controlled (60-84%)(8,11,12,17,32,34,35)
    • High blood pressure resolved (66%)(19)
    • High cholesterol improved* (94%)(11)
    • Obstructive sleep apnea resolved (76%)(12)

*Figure is for hyperlipidemia. Hyperlipidemia is a general term used for high fats in blood, which may include cholesterol and/or triglycerides.

What are some advantages and disadvantages of gastric bypass?


  • Can cause significant long-term weight loss (average of 62% excess body weight)(15)
  • Can lead to significant improvement of obesity-related health conditions(8, 11, 12, 17, 19, 32, 34, 35)
  • Doesn’t use a foreign object (like the gastric band) 
  • Limits the amount of food that can be eaten
  • Can cause significant changes to digestive organs and hormones that result in reduced hunger and increased metabolism
  • Permanent (won’t need more surgeries or readjustments, like the gastric band) 


  • Requires lifelong dedication to specific diet and exercise routines
  • Permanent (cannot be reversed)
  • More complex procedure than the gastric band or sleeve gastrectomy
  • Possible complications may include:
    • Vitamin deficiencies
    • Dumping syndrome (nausea, vomiting, or discomfort when eating too much food)
    • Ulcers

For more information on the risks of gastric bypass surgery, click here.


Metabolic and bariatric surgery is as safe or safer than other commonly performed procedures, including gallbladder surgery.(27,54) When performed at a Bariatric and Metabolic Surgery Center of Excellence, bariatric and metabolic surgery has a mortality rate of 0.13%. This means that out of 10,000 people who have this kind of surgery, on average 9,987 will survive surgery and 13 will not.(27) Gallbladder removals have a mortality rate of 0.4%. This means of 10,000 people who have their gallbladder removed, on average 9,960 people will survive surgery and 40 will not.(54)

All surgeries present risks. These risks vary depending on weight, age, and medical history. Patients should discuss the risks with their doctor and bariatric and metabolic surgeon.