I'm a bit on the fluffy side, and it's rarely seemed to be a problem. I guess it helps I have a rather pretty face, I know how to dress to flatter my figure, I carry myself with confidence, take care of my hair and skin.
There are lots of guys, I found, who prefer a bigger girl, or just don't care if you're big or small or average.
One time, on OK Cupid back in the day, this local guy caught my eye. He was super gorgeous, like almost a high-quality body-builder type, really fit, a firefighter/EMS dude. Smokin.' I figured I'd never stand a chance. I don't remember how, but somehow we hooked up.

(It didn't last long; we had different life goals. He literally wanted to buy a boat and sail around the world...)
My current bf is quite objectively handsome too, muscular, tall, long dreads and a nice beard.

He definitely prefers bigger women (and older women), so lucky me. He'd even be happy if I were bigger, but I don't want to gain because of health reasons, of course!
On the other hand, lots of couples who open up, generally guys whose female partners are getting lots of dates, and they aren't, get motivated to do their best to become more fit and attractive, go to gym or start a sport, watch diet, buy some new more fashionable clothes, get a decent haircut and beard grooming, etc.