Fine, here's more picture proof. The season order goes: S1, S3, S5, S6
Despite her jeans being more of a loose fit in S6, you can see that her weight isn't incredibly different from S1. I doubt wardrobe would put KK in clothes that didn't fit her so I don't believe that those jeans are baggy on her, but just that they're a different style from the normally x-tra tight ones they put on her.
I still believe that she has lost between fifteen and twenty pounds max.
If you want to see anorexic look at Teri Hatcher, Ellen Pompeo or Kate Bosworth. (or Keira Knightley or MK Olsen or Nicole Richie)
edit: ps the pics are from elegant-kristin.com, run by Jana.