ooohlookamountainofburgersimustconsume .... itis.
No disease will put weight on for you NONE.
There are those that increase appetite, those that reduce the burning down process thus leaving more mass on you, those that make it incredibly hard to lose weight once it's on.
There is, however, no disease known to man that will make you overweight on it's own without the help from a massive pile of food.
The only exception (but not a disease) is child birth, not really along the same lines but some women keep a bit to a lot of the baby weight they gained during pregnancy. It can't be helped.