A girl with bad fat eats fast food every evening followed by a Ben&Jerry's. This contributes to bad fat which gives her a huge flat ass, hanging boobs, sticking out belly, and in the more severe cases a double chin.
These types of girls are bad catches and should be avoided, unless she is a friend of a hot girl of course...
T: Hey man, check out that girl's ass! I wish i could rip those jeans off and do her all night!
J: Nah man, that's bad fat... You don't want a sumo wrestler doing you all night do you?
Refers to the kids who grew-up during the explosion of the media and social aspects of the internet, causing them to spend so much time in front of the computer screen, that they do not get any exercise and eventually become obese.
I went to my nieces track meet at the high school, and ALL of the girls--in the stands, AND on the track team---were fatter than The Michelin Man!