I won't say it's 100% correct, but there's always the notion that convicts or homeless dudes always sleep with big girls.

How many $100k+ men are out there really dating fat women?
I work around a lot of White collar people being White collar myself and best believe those men making stacks are putting their women through many diet and exercise plans after child birth.
Rich men don't play around with that stuff. They're pretty vain and concerned about the image of being with a chunky woman even if the weight is mostly correlated with pregnancies.
Broke or working class men are much less judgmental towards fat women because they tend to live in environments full of heavier women that they went to school with, lived on the block with, hung out with, etc. So, to them, fat women are just plain ol women to them whereas, in the suburbs, fat women stand out as being perceived as "lesser" than other women.