YOU SAID:

i have a cat who is fat and he eats rats

INTO JAPANESE

私は太っている猫を飼っていて、彼はネズミを食べます

BACK INTO ENGLISH

I have a fat cat and he eats mice

INTO JAPANESE

私は太った猫を飼っていて、彼はネズミを食べます

BACK INTO ENGLISH

I have a fat cat and he eats mice