Gastric bypass (RY-GBP) has a very small gastric pouch with a 1-cm diameter Roux-Y gastrojejunostomy. RY-GBP is associated with early satiety and an aversion to sweets secondary to dumping syndrome symptoms and has a significantly better weight loss than various gastroplasty procedures, including the vertical banded gastroplasty. However, it may be associated with vitamin B-12 deficiency and iron deficiency anemia in menstruating females, preventable with prophylactic oral iron and vitamin B-12. With an 80% 5 y follow-up, RY-GBP patients lose two-thirds of their excess weight within 2 y, 60% at 5 y, and greater than 50% at 9 y. The RY-GBP can be beaten by nibbling "junk foods" (potato or corn chips). Conversion to a malabsorptive procedure may cause severe malnutrition and fat-soluble vitamin deficiencies and should be used only for "superobese" patients who fail a standard RY-GBP and have severe comorbidity. RY-GBP is the most effective procedure for morbid obesity, especially in patients addicted to "sweets."