AMERICANS don't eat so much as feed; they graze happily all day long. Walking on the beach last Sunday, the evidence was all around. Families turned up with their giant coolers and set themselves up on picnic tables with portable charcoal broilers, bags of hamburger buns, cans of beer, to the sound of crinkling cellophane as packets of crisps were torn open.

Two elderly gentlemen sat on plastic chairs hard by their cars and the dialogue went as follows: 'What do you buy at Christie's?' (A grocery chain.) 'You know: milk, ice-cream, that sort of thing' - for some marketing board long ago sold Americans on the benefits of milk, and no one told them they really ought to stop when they reach (if they ever do) maturity. I saw, on my walk, three or four of the grossly overweight, fattened by all that dairy produce, arms and legs in rings of Ubangi fat - and of course, since Americans are utterly unselfconscious, wearing Lycra stretch pants.

That night we went to the cinema. No one goes in without a tub of popcorn the size of a water- pail; a medium Coke comes in a quart-sized paper cup filled to the rim with crushed ice. In the office the next morning, someone brought vast doughnuts, miniature sweet lifebuoys for a second and continuing breakfast; at lunchtime the thousands drifted in the muggy heat towards the ballpark clutching franks that dripped with onions, great soggy slices of pizza. Bread, spongy, covers everything. The feeding is continuous, ambulatory; everything is covered in something else, and that something else comes from the supermarket cornucopia; one doesn't so much cook as unzip, pour, squeeze.

America's is a food culture of plenty based on a history of want. The great national holiday is Thanksgiving, celebrating the delivery of the first colonists from starvation. Food simply satisfied appetite. There was no thought of refinement or of creativity with food. Who would have provided such a concern, when just getting food was a sufficient difficulty?

As the country expanded westwards and lurched towards posterity, the frontier remained in the American mind: settlers settled and had to wait for crops to come up. Only cattle and game were reliable sources of food, and staples that could be transported in wooden barrels, sorghum that grew weevils, corn (maize) flour that could be moistened and baked. The frontier woman (and there were three men to every woman) was expected to till and raise, and when finally there were enough women, via immigration, enormous stretches of the country were implanted with hard-boned wives from Scandinavia and Germany, bringing with them a culture of milk and grain. The meat got plonked on the fire; plenty was a rising loaf. Every aspect of food production had to be geared to size and satisfaction of appetite rather than taste and satisfaction of the palate: the 50lb watermelon, the Idaho potato, the fist- sized strawberry, the stack of pancakes, the foot-long frank.

In the cities, successive waves of migration brought and marketed a dozen cuisines: Jewish, Italian, Mexican, Chinese. In this century, and accelerating with the second world war, blacks, emancipated from the farms of the south by war industries in the north, added another element to the palimpsest of American food. The process goes on to our day, adding Russians and Vietnamese, Hungarians, Czechs, Haitians.

If America eats constantly, it also eats imperially, converting such foods from its immigrants as are portable and quickly consumed: hamburger and frankfurter early, to be followed by burritos and pizza, chilli con carne, dim sum, corn dogs, meatball subs, pastrami, coleslaw, kebabs. To eat one's way through subject peoples, to become gross on convenience, to have not meals but the quick-food fix.

Such has become the way of the common American feeder. 'As you know,' a colleague said to me yesterday, 'smoking is the vice of the poor.' Yes, I wanted to say, so is the kind of food that develops fat and cholesterol, that clogs the arteries and thickens the thighs with cellulose. For all that generality of food in America, that vast array of chemically induced, appetite-arousing odours, those violent, sweet dressings, those dollops of aero-foamed creams, those rows of brand-names, of breakfast cereals and 'fresh' or 'like Mom used to make' goodies, belongs to one level of American eating: that of the extreme, levelling democracy in which Americans like to believe they live, and therefore, perforce, eat.

Of course, by now, at the heart of the empire, there are at least two other food cultures: the culture of fear (known as 'health') and the culture of ultra-sophistication, to which all the rarest things of this world are brought, a world in which every conceivable object for haute cuisine stocks the shelves of specialised stores, where one chooses from a hundred coffees (but still can't make a decent cup), where one mixes abalone from the north-west with lemongrass from the deep south and pigs out on truffles and the costliest wines.

The former is deeply anorexic; it reads labels intently and heeds the warnings of the Food and Drug Administration, believes in Ben and Jerry, eco-marketeers with an interest in rainforest nuts; it is squeamish about eggs and poultry, repelled by additives, watches its monosodium glutamate, subscribes to diets, concocts its own yoghurt, mixes its own muesli and struggles with school boards to eliminate French fries from the midday meal.

The latter is jaded and travels the culinary world on successive nights, knows its way to the Beaumaniere and finds the picturesque in huachinango grilled in central Mexico. But it lives apart from basic American eating, which partakes as much of the trough as of the table.

And this, I think, is the way with dominant empires just as they begin to topple into oblivion. There is the large mass that is justifiably satisfied to be beyond starvation and finds ideological satisfaction in that fact (America the bountiful, with its 'fields of amber grain') and then there are the masters, torn between guilt (expressed as political correctness, so that one doesn't eat Chilean grapes or drink South African wines, lest one be contaminated with the evil of the world) and the pure hedonism of possessing all the world's treasures.

The masses are gross and in ill- health, much of it dietary in origin; the elites are svelte and selfconscious and earnest and can afford to eat well, if seldom very well. It is a rich and contradictory concoction, food in America, a place where the rich eat less than the poor and the dinner table, restaurants apart, is nearly a thing of the past.