Yes, I agree with this to a certain extent. Until I fell pregnant with my daughter, I was slim - never skinny, but a size 12. I always had men interested in me, and never struggled to 'pull', as it were. I had my daughter at aged 22, and had gained five stone.

I spent almost the whole of my twenties overweight, and although I was still fairly confident, I certainly didn't get much male attention. I was married though, so it wasn't a 'problem' as such. I split with my hubby and got down to a size 16 - I actually looked okay at this size, as i've always carried my weight well. Again I began to get more male attention, and began seeing my current partner. I went back up to a size 22, but thankfully, my OH didn't even seem to notice - I guess that's love's rose-tinted glasses though! I know I got treated differently elsewhere though.
Anyhow, in July 2005 I reached my goal with CD, and have been a size 10-12 ever since. Again, I now get lots of male attention, which is always an ego-boost, even if I don't want to do anything about it! I work in an environment where no-one has ever known me at a larger weight, but i'm sure I would be treated a little differently if I was bigger. Funnily enough, my OH's affection has never changed with my weight loss, but that pleases me as I know he loves me for 'me'... if that makes sense.
Ironically, my ex-husband who also always struggled with his weight has gained loads since we split - probably around the 5 1/2 - 6 stone that I lost. It actually saddens me a bit to see him like that, as he's the father of my children at the end of the day, and i'd prefer to see him fit and healthy for them.
I can understand the 'attractiveness' issue, because, if i'm honest, I think most men and women look more attractive at a slimmer weight - not a size 0, or even a size 8, but once people get to 3 tone overweight or more, it does tend to have an affect on their attractiveness... IMO.
It's a shame that our character's are judged by our weight though, as that's just ridiculous. I guess just it's another stereotype though, and they're hard to combat.
Jo x