Typically, a gastric bypass surgery involves a 4- to 6-day hospital stay and 2 to 3 days for a laparoscopic approach. Most people can return to their normal activities within 3 to 5 weeks. Gastric bypass surgeries may cause dumping syndrome. Dumping syndrome occurs when the small intestine fills too quickly with undigested food from the stomach, as can happen following gastric bypass surgery. This occurs when food moves too quickly through the stomach and intestines. It causes nausea, weakness, sweating, faintness, and possibly diarrhea soon after eating. These symptoms are made worse by eating highly refined, high-calorie foods (like sweets). In some cases you may become so weak that you have to lie down until the symptoms pass. After gastric bypass surgery, you will need to train yourself to chew your food thoroughly, eat slowly and not overeat. Talk to your doctor about the exact level of risk gastric bypass surgery may pose for you. As with any major surgery, gastric bypass carries risks such as bleeding, infection and an adverse reaction to the anesthesia. A risk of death has been associated with gastric bypass surgery. It's important to follow your doctor's directions in preparing for gastric bypass surgery. Bypass surgery in unresectable distal gastric cancer. However, it does not have any of the risks of nutritional deficits associated with gastric bypass surgery. Risks common to all surgeries for weight loss include an infection in the incision, a leak from the stomach into the abdominal cavity or where the intestine is connected (resulting in an infection called peritonitis), and a blood clot in the lung (pulmonary embolism). About one-third of all people having surgery for obesity develop gallstones or a nutritional deficiency condition such as anemia or osteoporosis. Most people who have gastric bypass surgery quickly begin to lose weight and continue to lose weight for up to 12 months. One study noted that people lost about one-third of their excess weight (the weight above what is considered healthy) in 1 to 4 years.1 Although some of the lost weight may be regained in time. The laparoscopic approach showed similar results, with 69% to 82% of excess weight lost over 12 to 54 months.