You are absolutely correct about the fat house cats - but unless they are outdoor cats from the beginning, depending on where you live, at least they are safer.
I buy them the best human grade food possible, and also grow wheat grass for them from organic seeds which I have purchased online. But, have not been doing that all their lives - we are only now, as a society caring better for our pets with better products for them, including holistic, and no preservatives, etc.
I guess, at the age of 14 I should leave them alone - is there somewhere on your site that there are directions and products for animals?