3 year old cat

Question
My 3 year old male cat has been gaining weight over the past few weeks.  Today he seems very confused and depressed. What could this be?

Answer
Michelle,
I'm not sure about the weight gain, but are you sure that he is urinating ok in his litterbox?  Male cats are notorious to get "backed up" and that will cause depression and could cause confusion. One sign that they are having a problem is they will frequently go to the litter box, strain to pee, but do nothing.  The frequent trips is the thing to notice. (this can be fatal).
I think if I were you, I would take him to the Vet. If it is a urinary problem, he needs Veterinary care.
There is also a chance of diabetes, thyroid or other problems that need to be ruled out.  I'm not trying to scare you, but something is wrong, and the sooner you have him checked, the better he will be.