Sorry, just a correction to something Weeble said - the Gastric bypass is NOT new, it's one of the oldest weight loss surgeries there is. It was first performed in 1954, and there is LOTS of research on the effects of it long-term.
It is precisely because doctors have seen the after effects of it long term, that they take so many precautions with patients now and make sure to follow up their progress. They've also significantly reformed the way that the procedure is carried out, to make it less dangerous and to avoid some of the issues with the earlier procedures.
Weeble actually said the bypass as we know it now is still relatively new, which ties in with your post.
"They've also significantly reformed the way that the procedure is carried out"