You may be surprised, as I was, to discover that cats lack the enzymes to digest carbohydrates.http://www.catinfo.org/#We_Are_Feedi..._Carbohydrates
Once I knew this, I started feeding more canned and gave them a dry food which is the lowest I could find, Innova Evo, which is grain free.
I can't drop the dry food entirely, because Dear Husband is stuck at home with a chronic illness, and he can't stand the begging! But we compromise by getting the best dry food we can, and feeding canned twice a day. And fortunately, all three of the boys looooooove canned.
I get the Innova or Eagle pack holistic canned, but if we run out, I admit we get the Friskies or the 9 Lives (though not the gravy varieties) and also Fancy Feast, which they are fanatically devoted to.
It's great that you are paying so much attention to his nutrition. It does cost more, but they DO eat less of the good quality dry, I've found. I only need to pick up a bag every month or so, compared to twice a month with the supermarket brands.
And I'm confident my boys will have better health because of this. Diabetes, for instance, should be off the table, barring any serious disease. And that means a lot to me, since my beloved Bubby died of pancreatic cancer at the age of 14. That shouldn't happen again!