From Anne G Mirer, MPH:
Even with outcomes for which weight loss could be beneficial, the benefit will be temporary if and when the weight comes back. Quickly or slowly it will come back for all but a very few. The best most people can expect for their pain and suffering is to be about five to ten pounds lighter, and those are the minority for whom the treatment succeeds. It doesn’t matter how big a problem you think obesity is, and it doesn’t matter whether or not you’re right about it, because we do not have any tool that will make obesity go away.
Read the whole post – it might be eye-opening.