Pretty much agreed with the posts above, except that I think the gorean slave would be a little more in accordance to the 'fit-look' than some of you think. A little bit, at least. After all, it is clear that they aren't allowed to be fat (generally speaking) and they do get training that can be straining. They aren't sitting on their asses all day. Plus, they may dance, as well. As for Shakira... ýes, she has a bit of arm-muscle. Maybe her build would be rather close to what I imagine a panther girl's to be (more that than Boris Vanlo's heavily muscled female Arnolds on the book cover).
And I agree... there is mention of that 'belly' thing. So, I guess not the 'ideal' belly that renders the belly into little more than a slight tube around the spine. Yet, at the same time, how large does a belly have to be to be called a belly? I don't think Norman was typically thinking about anything that we (except maybe people working in the modelling/fashion industry) would consider 'fat'.
All in all, though... even though it is clear that there is a difference between the most notable 'beauty ideal' and Gor's/Norman's, I still feel that the 'beauty' described in the books is more 20th century west than anything else (which is only to be expected, of course).