I lost my weight the natural method. I have mainly kept if off but I have periodically put bits of it back on, but this is usually when my head hasn't been right, related to anxiety and/or depression - but when I'm right agin it usually comes off. A great book is 'The weight escape'. It is the diet book you have when you aren't having a diet book. It deals with the psychological approach to weight loss, something which is missing from pretty much any mainstream 'diet'. From the book, the main issues one can face is that they either do too much, deprive themselves, which isn't sustainable, and fail; or they won't make enough changes and the difference is indiscernible. Also, the book suggests that weight management occurs one decision at a time. If the sum of your choices are mainly pro-weight-loss, you'll lose weight and keep it off. If they are geared towards weight gain, you will gain weight. That being said there can be environment and biological factors that we have little control over. I have read a study where the glues/inks used in a takeaway coffee cup have a correlation to weight gain - it is thought that the chemicals stuff about with your weight control hormones. But obviously, further studies are needed.
GI surgery can work but it is quite major, and has a few risks of complications. Success rate I hear is 50% which on a population wide scale is the most successful form of long term weight control (weight watchers is a mere 20%). GI can work if you learn to eat intuitively - if you continue to stuff your face to the point of sickness or discomfort, it won't work, for your stomach will stretch etc.
As for eating clean - I find if I have large amounts of rubbish, next time I go running, I will get shin splints and/or runners belly. Severely. There's nothing like needing to **** your brains out when the nearest loo is still a 3km/16min run away!
ahh *sigh* those were the days.....