Graphic of a gastric bypass using a Roux-en-Y anastomosis. The transverse colon is not shown so that the Roux-en-Y can be clearly seen. The variant seen in this image is retrocolic, retrogastric, because the distal small bowel that joins the proximal segment of stomach is behind the transverse colon and stomach

This variant is the most commonly employed gastric bypass technique, and is by far the most commonly performed bariatric procedure in the United States. The small intestine is divided approximately 45 cm (18 in) below the lower stomach outlet and is re-arranged into a Y-configuration, enabling outflow of food from the small upper stomach pouch via a "Roux limb". In the proximal version, the Y-intersection is formed near the upper (proximal) end of the small intestine. The Roux limb is constructed using 80–150 cm (31–59 in) of the small intestine, preserving the rest (and the majority) of it for absorbing nutrients. The patient will experience very rapid onset of the stomach feeling full, followed by a growing satiety (or "indifference" to food) shortly after the start of a meal.