I think I'm detecting a theme here:
I sort of qualify: I'm 5'4" and a size 10 (12 in teenager's shops). Although I am heavy at 10.5 stone (I think I'm just denser than the average human being)
Why?
It's partly genetic (my mum is very slim, my dad less so).
After one dreadful experience in my late teens I have never dieted. I find it distorts my relationship with food so much that all I can think about is food, all the time. Total torture and so boring.
Instead I do quite a lot of exercise (running, yoga, cycling) so I don't have to worry about food quantities. Since I know it won't be an issue, I relax and find that naturally my portion sizes have become smaller. Curiously I also seem to have an instinctive preference for veg/carb based dishes (although normally larded with a goodly amount of fat!)
Food is not a comfort for me: how much I want to eat is completely divorced from how I am emotionally. In fact if I'm upset it completely destroys my appetite
Also, there's definitely a relationship between how busy I am and eating. If I'm busy, eating is a low priority (although curiously, cooking isn't - puzzling huh?)
I don't like to think of people who hold weight as doing anything 'wrong'. It's a mindset thing, which I've been lucky to have for years, and I'm not really sure how to suggest others could go about cultivating it. My only observation is that dieting seemed to send me down totally the wrong track and definitely didn't work for me.