Does he drink a lot of water?  Is he urinating a lot?

Excess hunger is one of the signs of diabetes and a few other
endocronological orders..   If this is something new, I would highly
recommend a trip to the vet for a quick once over.

They are doing studies, that show that dry food is pretty much the
equivalent of mcdonalds food for kitties.  It has too many carbs, and cats
can't processes those very well.  You might want to consider switching over
to a high protein low carb wet food.

But if you feel you need to stay with dry, look into nutro's line.  They
have a 'light' formula.