At my old job, my manager and I would eat lunch together nearly every day. I would bring low-calorie, low-fat food I cooked at home or a Lean Cuisine/Weight Watchers frozen dinner and she would go to a fast food place and bring something back to eat. She never brought her lunch from home. She ate things daily like 2 chili cheese dogs with chili cheese fries and a coke or even if she got a salad, she'd order the kind with fried chicken strips on it and an extra full fat salad dressing. She hated exercise and refused to join a gym. She rarely cooked at home and ate most meals out. Yet she was a size 2. I went to the gym 5-6 days a week and counted calories and could never get below a size 14-16.
I went through a depression and ended up gaining back what I had lost. Of course this led to more depression which didn't help things. I ended up having lap-band surgery. Don't get me wrong...I'm happy to have done it and wouldn't change a thing...but 17 months later I'm a size 14-16. My 15 year old son, who barely weighs 100 lbs, eats at least double what I do at each meal (I can only eat about 2 cups of food max in an entire day) and I still am not losing weight. My body has apparently decided it likes being a size 14-16 and doesn't want to budge. Due to recent health problems, I haven't been able to go to the gym for a few months, but as soon as the doctor releases me I'm going back and I'm hoping it helps me to get a bit more weight off.
I hate when people who have never had a REAL weight problem in their entire life tell me it's all down to eating less and exercising more. Yes, it is but just how much less food and how much more exercise? 99% of the people spouting this wouldn't have to work out every single day and eat fewer than 1000 calories a day just to maintain their weight. So, if my body decides it likes being a size 14-16 and I stop losing weight, do I go down to 750 calories a day and work out for 2 hours a day? Would a naturally thin person do that and be able to keep it up? I doubt most would. Thin doesn't automatically equal disciplined any more than overweight equals lazy.
I love food and I don't always make the best choices but I would bet that a lot of the judgemental people don't either. They've just been lucky enough to inherit genes that they don't have to exercise constantly and feel like they're starving all the time just to maintain a healthy weight. And I have known several naturally thin people who just plain didn't care about food and would even forget to eat.

That would never happen to me.

But it wasn't because they were so incredibly disciplined. It was because, for whatever reason, their bodies didn't demand more food. Lucky them.