No, really, thanks-- for all the great suggestions! Now I don't know where to begin. Thanks for that, too.
With that in mind, I think I'll just start in the order I received them-- which means, Susan, you're up. Excuse me while I channel The Dog Whisperer here, and bear with me!
This is a hard question to answer over the internet, without meeting or seeing your dog engage in this behavior, but I'll do my best. And I do mean my best-- I'm not a pro dog trainer, not by a long shot. But I do have a really good understanding of dogs, and where their behavior stems from.
I'll start with wolves.
Wait! Come back! It makes sense, I swear!
See, wolves are the best and purest example of the domestic dogs we know and love-- and share our homes with. Wolves are distilled dogs, and once you understand them, you can understand yours.
Wolves have EXTREME pack hierarchy. Not "EXTREME!!!!!" as in, you know, 720's on a snowboard (though how awesome would that be!), but extreme as in dramatic. Wolf pack hierarchy is structured like this: there is a male and female alpha, each in charge of their respective genders and the pack as a whole, and more dominant than the rest. The other wolves show their respect for the alpha by allowing them to feed first, rolling on the ground and showing them their belly, or licking their chin. The alpha will bring uppity members into check by biting their snout. If an alpha falls ill, gets injured, or starts to show weakness or age, the rest of the pack will test their dominance.
There is a beta, gamma, etc., for purposes of human thought. Most of the time, once a wolf has established its place in the pack, the pack remains quiet and in order. There are occasional spars and testing between lower-level members, but the order remains. However, if an alpha is lost, or a new loner alpha attempts to join the pack, it can throw their social order into chaos.
Wolves, like people, are always looking for opportunities to improve their status in life. And this is where wolf interaction with humans comes in, and where I start to get back to your dog, Susan. I once got to observe wolves interacting with humans as a volunteer at a local organization for wolf conservation and breeding.
Wolves (like most animals) don't really know what to make of humans. We aren't like them, but we are dominant. But because it is in a wolf's nature to test the dominance of another creature, particularly a creature it doesn't understand, a wolf will test your dominance every time it greets you. So, when one of the wolf keepers would go into the enclosure of the "habituated" (read: safe to interact with, sort of wolf ambassadors) wolves, the wolves would react with tests of dominance each and every time; generally by jumping on the person. It didn't matter that this was the same person each day. To a wolf, hierarchy is all there is, socially.
So, how does this help your problem, Susan? Well, it doesn't, specifically, but what it does demonstrate is the basic cause of all domestic canine misbehavior-- dominance. Your dog, when it barks for people food, is saying, "Hey! You're supposed to give me food when I do this, because I'm in charge around here! Why are you eating without me? I'm the alpha!"
So, what can you do about this? Well, again, it's hard to say without knowing your dog specifically, or the other kinds of behaviors they exhibit-- do you have trouble with them in any other areas? Do they pull on the leash, or jump on you when you get home, or bark for attention at other times? All I can really suggest is to watch for other situations where your dog may be getting validation that they are, in fact, in charge (not even intentionally)-- do you pick them up or scratch them or even yell at them when they jump on you? Any attention is good attention, with most animals. If you can find other places where they may be getting attention for bad behavior and eliminate those, you may find your dog will respect YOUR dominance and stop barking for food, too.
This was long, if you made it this far you deserve an e-cookie. I hope it helps at all!