I've been overweight my whole life up until now. My HW was 185, and though it doesn't sound very high, I was around 5'1 when I weighed that much. It didn't sit well on me I guess, and the rest of my appearance was kind of neglected because I was fat and figured no one would even notice the other flaws, because being fat was bad enough already.
I'm only 16, so it's not like I've had a lot of opportunity to date, but I've yet to have a boyfriend/first kiss/whatever. At my HW, a boy would see me for a second and I could just feel the friend-zone coming in all around me. Dating, it seemed to me, wasn't a thing normal people did, but a thing movie-star-good-looking people did and them only. I obviously didn't fall into that category and I didn't even think I'd get a boyfriend ever in my entire life.
Then I met a guy who seemed to show interest in me, but I couldn't bring myself to show too much interest back because I knew I didn't have the confidence for a relationship. So I decided to lose weight, because I wanted to like myself enough for others to like me. He and I drifted apart (sad thing, actually) but I'm infinitely more confident and people show interest in me, they smile at me, they casually flirt with me... it's almost surreal. I don't think I'll ever be a 'casual dater' but I sure am not objecting to casual attention.
I guess my point is like what everyone else said, no one will date a fat girl who spends all of her time wallowing in self-pity. No one is really inclined to date a thin girl who wallows in self-pity either. I knew I could never be confident with all my extra weight, so I've worked to get rid of it. Now I'm gaining confidence. A fat girl can definitely score if she is confident and makes an effort to look presentable (make-up if it makes you look better, combing hair, showering, etc.).