My ex weighed 170 (she told me later and I could barely believe it but I guess she carried it pretty well and never wore revealing clothes) when I first met her in Psychology class in college. By the time we started dating she'd lost about 45 pounds (we were together for six years and are still friends in case anyone is interested

, I hate when couples end up hating each other

).
So, don't dismiss a girl just because she's fat. Have faith (reasoned expectation, whatever) in human nature. People can turn things around and if you're ever in hard times you'll be glad she can keep weight on easy (she'll be cheaper to feed and will still be able to maintain enough body fat to nurture a baby).
Look at this chick for example (no, that's not my ex). :
It's pretty amazing what people can do when motavated. A person's "template" (physical, mental and emotional) is more important than where they are now.
That and their ability to self-motivate (admittedly an issue of mine though my persistence, albeit sporadic, dashing good looks & charming nature usually make up for it, that's probably not a good thing though

).