I found this at another site...
Dumping syndrome is one of the most common conditions that occur after gastric bypass surgery. Dumping syndrome is characterized by nausea and vomiting, weakness, fatigue, sweating, diarrhea (sometimes severe and right after eating), and feeling faint. Food nutrients and calories are absorbed in the small intestine. As the top portion (duodenum) of the intestine is bypassed in the surgery, there may not be time to absorb the food, making it pass right through, causing diarrhea. Many of the other symptoms, such as sweatiness, weakness and fatigue, are direct results of the body not absorbing the nutrients it needs. Proper diet and the daily intake of a multivitamin will help with these symptoms. Hopes this helps, Nancy