Gastric bypass surgery is designed to decrease the stomach’s size to make food “bypass” part(s) of the small intestine {small bowel). The stomach is made smaller so that the patient can feel full from less food. This reduces the amount of food you can consume at any one time. Part of the small bowel is bypassed to reduces the amount of nutrients that can be absorbed from the food you eat. This ultimately leads to weight loss.

There are two types of gastric bypass surgery: extensive bypass surgery and Roux-en-Y gastric bypass.

1. Extensive bypass surgery 

This is the most complicated gastric bypass. The surgeon cuts off the lower part of the stomach after which he connects the remaining small pouch directly to the end part the small intestine (the ileum), bypassing the first two sections completely. It is very effective for weight loss for the morbidly obese, but it is not widely used because it has high complication rates and can leave the patient with nutrient deficiencies as very little food gets digested and absorbed.


2. Roux-en-Y gastric bypass

This is the more common type of gastric bypass surgery. It is less complicated and patients enjoy quicker recovery times. To execute the Roux-en-Y gastric bypass, the surgeon staples part of the stomach together to leave a small pouch. The size of this pouch is often limited to being able to hold only a cup or so of food. With such a small stomach, the patient will feel full quicker. This control strategy is referred to as “restrictive” since the reduce stomach size restricts the amount of food it can hold.

The next stage of the surgery involves creating the bypass. The surgeon cuts the newly created stomach pouch from the rest of the stomach as well as the duodenum (first section of the small intestine). He then connects the pouch to the second section of the small intestine located slightly farther down (called the jejunum). The is called executing the “Roux-en-Y.”

After Roux-en-Y is performed, food passes directly from the stomach into the jejunum, thereby completely bypassing the duodenum. This effectively curbs the patient’s calories absorption abilities and is referred to as a “malabsorptive” weight control measure.


Both stomach binding and Roux-en-Y are performed during the same session and the two procedures are together referred to as “Roux-en-Y gastric bypass. In most cases, surgeons perform both laparoscopically (using surgical tools inserted through incision in the belly. When this is not possible, he procedures can be performed laparotomically (accessing the stomach and intestines via large cut in the middle of the belly).

Why it is important

Weight loss surgery is suitable for individuals who are severely overweight and have been unable to shed the extra pounds in spite of exercise, diet or other procedures recommended by medical practitioners. Doctors normally start considering surgery as a weight loss technique when the patient’s BMI (body mass index) reaches or exceeds 40. It may however, still be considered for individuals with slightly lower BMI who have a disabling or life threatening problem such as type 2 diabetes that makes it harder to control weight with diet, or exercise.