I've read that the average American woman is 5'4" and weighs 140 pounds and the average model is 5'11" and weighs 117 pounds.
Just thought I'd throw that out there... ;)
Look at lainie's post above...Marilyn Monroe was 5'5 1/2 and 140 lbs (at her heaviest). So, I guess that bears out that MM would be considered 'obese' by todays flights of fashion (ie., gay men who want to make women look like 12 year old boys). Marilyn would be, ahem, a size 14. I rest my case.