Well, true, a good percentage of gastric bypass patients get reactive hypoglycemia which means you feel really crummy after eating a plethora of foods, not just sweet stuff. (The patients refer to this type of becoming ill as "dumping")
The problem is, if you are getting sick after eating and you lose weight, that doesn't really count. Because cancer patients and terminal AIDS patients also lose weight from being sick, but it's so not worth getting sick to lose weight.
What they are hoping you don't know about is for one, the Roslin study which found that 3 months after a gastric bypass, the appetite comes back worse than before surgery in many patients.
This clinical study of 63 gastric bypass patients (that means the researcher, a gastric bypass surgeon himself, actually examined the patients), also found that many of these patients had "glucose abnormalities" which would, in part, explain their voracious appetites.
Bottom line - to lose weight by getting sick after you eat? Life is just too short for that one, you may well find. 5% of people on non surgical diet nutritional programs can keep off the weight. 7% of weight loss surgery patients (all surgeries, several studies) can keep off the weight. But that extra 2% which isn't very much of a differential, is counting those with "glucose abnormalities" and other health problems after weight loss surgery.
Dr Terry Simpson tells us that success with Weight Loss surgery (any procedure) is 10% the surgery and 90% the patient.
So after taking rather serious and sometimes life threatening risks to have one's digestive tract rearranged, you can see that it is not very much more effective in keeping off weight than is a non surgical program.
Looking at things this way, the seeker should also be aware that merely embracing a healthy lifestyle of mostly wise food choices and cardio exercise 5 days a week will keep you healthy at any weight.(Lee CD, Blair SN, Jackson AS. Cardiorespiratory fitness, body composition, and all-cause and cardiovascular disease mortality in men. American Journal of Clinical Nutrition. 1999 Mar;69(3):373-80)
Ask yourself, in view of the foregoing, is weight loss surgery really worth the risks?