actually i don't know why thread starter have to ask this question. it a common knowledge that slim gals are more attractive at least to majority of the people(men and women alike).
that why slim gal are covered everywhere be it magazines / movies / TV / commercial etc out there. although attractive does not mean it THE choice for sex but for most of the cases, yes. i think it true. of course, by slim i assume you do not mean those suffering from anorexic
but average proportional gals that does not carry excessive fats that should not be there.
it not an right or wrong issue. it just natrual selection. people with healthy weight be it guys or gals is just more attractive as they are being seen as a better choice for mating. it all wired in our brain.
as for most people but not all, science is telling us a bigger part of being overweight is a lifestyle choice or habit rather then genes although it does play an important part.