I was wondering about that. The joints on either side of the kidney area make the loin area look cheeze-fond when it may not be fat in actual diameter, so it's not just the butt acting all on its own. (That's a phrase that's bothering me a bit...)
I believe the shoulder blade musculature (trapezius etc.) and the arms are voting along with the cheez impression.
So this is a realistic body, not a fantasy ripped-and-cut body, right?