Thanks everyone for your ideas and comments!

I am not sure what breed Stewie is, other than Heinz 57. His coat has some characteristics of a Russian Blue (that thick shimmery silver coat), but his brother was solid black and sleek. Both he and his brother are big guys - tall, with large heads and paws. But he is definitely overweight, even for a large cat.

With the new kitten, he is getting more exercise. We discovered, though, that he has been sneaking her (much more calorie-dense) kitten food. So we've put her food up high so that he will be less likely to eat it (and if he does eat it, at least he'll have to jump up to get onto the ledge where it is). I'm hoping that will help. Of course, I suspect that she is sneaking his food, too, so we've got to get the food sorted out so everyone's eating their own.

As soon as I get a chance to go to the pet store, I am going to see about getting the Innova and a leash. If we switch to the Innova, do you think there is a problem with feeding Stewie and the kitten the same variety? She is about 12 weeks old. He is about 5 years.

I'll keep you updated. And thanks again for all of your interest and help!!