There have been no long term studies on the effects of weight loss surgery.
There can't be any because the procedures haven't been around long enough. Do the procedures really prolong life? Do they increase quality of life? I am not convinced it's worth the risk especially as other than physical restrictions I have no co-morbidities. I have no diabetes, no heart disease, no high cholesterol, etc. That's not to say they won't happen in the future, but for the moment, I am very lucky.
I've heard too many personal stories from people who have either had the surgery or knew a family member or friend who died or had severe side effects. I'm not talking about "a friend of a friend" stories. I'm talking real people who have lost friends and family to the surgery. Real people who have regained all the weight plus some - horror stories of malnutrition, vomiting, etc.
What are the true numbers of success? I doubt we'll really ever know as the medical profession likes to claim that the surgery works because it's a money maker for them.