When I was maybe eleven or twelve it came to me as something of a revelation that one could get through 'the holidays' (that is, the November and December ones, which at that time, at least in my culture, were the only ones celebrated with food) by eating only the usual amount at meals: the compulsion to stuff one's self, and then feel miserable for hours or even days afterwards, was illusory. Doubtless, I would have felt differently if I'd been chronically subjected to hunger, going for extended periods without enough to eat, or missing meals entirely sometimes; or if I'd had sufficient calories, but nutritionally deficient ones, subsisting on just grains and greens, say; or had sufficient but drab nutrition. In situations like these lie the practical motivations for feasting.
In Homer, the Greeks besieging Troy are pretty well fed. They've lots of porridge, bread, field greens, some olives and olive oil, and fresh dairy from the cows or goats they've brought along. Meat is something else. Raising or importing enough cattle to provide meat as part of the daily ration for a couple of thousand men is out of the question. Moreover, cattle are an important store of wealth, and in a sense sacred, having foregone some of their wildness to come under man's thrall, a concrete instance of the human connection to the natural world, and not something lightly turned into food. The workaround is to sacrifice an animal to honor a god - seeking a favor or giving thanks for one granted. The animal is killed as part of a sacred ritual which includes 'sending' the dead beast on high by burning it; but not really - just take a couple of major bones and some fat, and put that on the sacred fire, it'll make a lot of succulent smoke for the god. Cook the rest and eat it. There are vivid descriptions of the resulting feasts and of how the liberal food of unaccustomed quality lifts the participants' mood, making them better able to face the continuing war. No one asks how a god so easily fooled could be of much help.
These Homeric feasts show three functions of feasting. The connection of a feast with a significant event - here, a sacrifice - provides a means of using scarce resources rationally - of rationing them. The effects on mind and body of consuming this resource mark the occasion as one of celebration - perhaps somber, if asking a favor, more festive if giving thanks. And the feast is redistributive: it's not 'bring your own cow', the cattle are provided by the lords, and everyone (except the god, funnily enough) gets a fair share.
In different times and places, the relative weight of these functions changes. There were periods of the Middle Ages in Europe when famine was chronic. This lead to a proliferation of feast days, whose redistributive function was important in simply keeping people alive. We see something similar today in the collection baskets in supermarket doorways, and the heavily advertised holiday meal programs of certain shelters and churches, though this is much more a question of providing a fancy meal a couple of times a year than of pulling people back from the brink of starvation year around. When food is plentiful enough, redistribution can become an end in itself, as in the potlatch. Again, this is something one sees in our own culture, where often the point of a meal is not so much the guests' eating as the hosts' conspicuous consumption.
The connection between rationing and celebration is easy to see in our own edible environment. You'd think, given the general abundance of food, that rationing would be the last thing to the table, but have a look at the food sections of newspapers and 'family' or 'health' magazines in November and December: they're filled with suggestions on how to eat holiday style, without overdoing it. Essentially what's being discussed here is how to maintain a calorie budget while still tasting the bounty of holiday treats: what's being rationed is not the food, per se, which is superabundant, but the individual's access to it. The wise eater, we're advised, establishes how much they're allowed to eat ahead of time, then divides this up into eating events, which are carefully distributed across the menu of opportunities. At the same time, of course, there's the temptation to do a little tasting off the books, or, indeed, to simply forget about this budgeting entirely for a day or two.
This is a large part of celebration, to deliberately put aside all the strictures and nagging concerns of an ordinary day's life and indulge in the extraordinary, without thinking about tomorrow's return to soup and crackers, or whatever. This is strangely similar to the fascination with celebrity, which seems to allow those thus fascinated to ignore or transcend the inconvenient issues of the quotidien, be it a bad manicure, credit card debt, the war in Iraq, or the government illegally reading your mail, through a vicarious participation in the made to order lives of the rich and famous. And vice versa.

FOOD OF THE WEEK - Overeating