It seems as if my four-person family is going through food a lot faster than previous four-person families have.

The only change I can think of is that I've hired the maid and gardener for them. Since the maid and gardener don't live in, I assumed they brought their own lunches or went out for lunch or something. Do the maid and the gardener consume household food units?

I don't think the maid & gardener eat your food. From what I have seen, at least. My brother has a maid and gardener and I don't have either and we've wondered before. From what we can see they don't eat. Hope this helps