When I was younger I had a cat who was a little over weight (She gained a lot of weight after she was neutered) and she always wanted to go outside. We got her a harness so she can be in the backyard but after 5 minutes, she somehow slipped out of it. I'm not saying that they are not safe because they have improved since 1998, but I think that your cat will appreciate going outside. I don't think that you should really "walk" them but let them go around the yard because the grass is really good for them and they get fresh air. Ever since my first cat, which was the over weight one that we called Kiki aka "Fat Cat", almost every other cat I had always went outside without a harness or leash. Ozzy, Toby, Laylo, and Patches all went out side regularly, never wandered away from the house, and always came back when they were ready. They even brought us back a few presesnts... well dead rodents really. But, in my opinion I think it is ok to use a harness or leash if you are afraid to let them out alone(especially if you live in a city, i live in the valley with not so much). I'm not saying to let your cats out either.. I am just sharing my story and giving my opinion. Thank you if you read my post too.. it's a little long