Not to get too technical about it, but there is an actual measurement which is considered attractive by men of diverse cultures and socioeconomic backgrounds. It's a ratio, so theoretically holds for both the Twiggies of the world, as well as the more Rubenesque. It is the waist to hip ratio (circumference at the narrowest point of the waist divided by circumference at the hip), and the "sweet spot" is .7.
The Rubenesque, in the flesh, as I have had the chance to examine through my life as a plastic surgeon is more ummm...., errr..., able to elicit automatic discrete changes in topical blood flow dynamics than one would guess from a painting or a picture.
Slimming down is not always the answer. Who in good conscience would slim down Christina Hendricks of Mad Men fame?

http://crookedtimber.org/2012/06/13/body-monoculture/

Some comment

I think all types can look good.

i do like slender women, but my niche has always been fit women.

It depends on the lady, what kind of presence she gives off. I've seen larger buxom ladies radiate sex appeal, where waif like cat walk models have none. 

Christina Hendricks oozes sex appeal and I find that type extremely attractive, then I married one.

Albert Vargos had pretty much the ideal woman defined in his pinups:

http://www.thepinupfiles.com/vargas1.html

Shame she didn't actually exist, except in his imagination and artwork.

I always said, before I got married, the ideal female body was the one in bed next to me.  Then 4F Hepcat then I saw the lady of my dreams I married her.