The cat's not fat!
You should see his nephew, that one is fat! (will post a pic later maybe).
He's actually quite slim. For a Karthäuser male that is.
I am not sure about the actual weight, because he's officially my sisters cat. He just spends most of his time in my appartement and follows me around outside when I'm home.
But should be somewhere over 8kg at least. Which is not much for such a tall cat (should put something next to him, so you get the right scale... like my sisters dog. A Chiwawa...
).