Boxing Day mirrors reflect the waistlines of sin. Gluttony induces guilt. Post-Christmas pundits preach the penitence of indigestion and display diets designed to redeem us from overeating. At exceptional extremes, excess can inflict obesity, squeeze the heart and play havoc with blood sugar. Like every relaxation of restraint, it activates moral angst. Really, however, at most levels of indulgence, and by comparison with other forms of naughtiness, gluttony is rather good. Apart from lust, which propagates the species, it is the most useful of the Seven Deadly Sins. Indeed, it has been essential for the survival of humankind and the triumphs of civilisation. It is time to rehabilitate gluttony. We would not be here without it.

Gluttony is a gift of evolution. In the struggle for survival with other animals, human beings have always had two severe disadvantages: feeble bodies and simple digestions. These restrict our cycle of energy production by limiting the range of food sources we can absorb. Big meals are a form of natural compensation, stoking our energy generators with ample fuel. That is why we evolved ways of exciting appetite: ours is the only species which dresses food to make it more appealing to the palate. Our bodies, moreover, are designed to make the most of our excesses by storing the benefits as fat. On average, the body of a normal, healthy person in the developed world contains relatively more fat tissue than that of a penguin or a polar bear. Whereas most animals concentrate their stores of body fat in one or two parts of the body, we have multiple deposits, spread generously all around our frames. Human beings are designed by Nature to be overeating animals.

Food is a social lubricant. Big meals have always been occasions of conviviality and social bonding. The earliest evidence of binge feasting has emerged from a Stone Age rubbish dump outside the cave of Altamira, in Spain, where hunters decorated the walls with brilliant images of animals they slaughtered. In that era of abundant game, they killed far more than they could eat; so the Christmas luncher who takes a wickedly, impossibly big helping is in a great tradition. In a comparably ancient cave at Laussel, France, a buxom “Venus” revels with a horn of plenty raised: she obviously got fat by enjoying herself.

In Neolithic times, chains of food distribution were social shackles. They linked relationships of dependence. They restrained revolutionary tendencies and kept client classes in their place. The biggest feaster was the chief, for he could oblige the biggest following. The rich man’s table recycled crumbs. His waste fed the poor, while his demand attracted supply. At the dawn of agrarian civilisation, gluttony helped to make it work. Early agrarian societies needed big eaters at the top to stimulate production and generate surplus — leftovers on which lesser eaters could feed. So as long as the food supply was unthreatened, a gigantic appetite was a sign of heroism and justice, similar to prowess in war and piety in religion. At the greatest banquet of antiquity, a king of Babylon served 70,000 guests with 14,000 sheep, 1,000 lambs, 1,000 fat oxen, hundreds of deer, 20,000 pigeons, 10,000 fish, 10,000 eggs and 10,000 desert rats.

It was important for the host to put on a good display of appetite. Legendary feats of eating were computed and celebrated by ancient chroniclers, like tallies of battle victims. As with other statistics compiled for propaganda, the figures beggar belief. Maximinus the Thracian, the 3rd-century Roman Emperor, supposedly ate 40lb of meat a day. A predecessor, Clodius Albinus, was said to consume 500 figs, a basket of peaches, ten melons, 20lb of grapes, 100 garden warblers and 400 oysters at a sitting. The tradition continued in the Middle Ages. In the old Icelandic epic, the Edda, composed between the 10th and 12th centuries, two heroes engaged in an eating contest to establsh which was fit to rule: the winner ate “all the meat and bones and the platter itself”. In the same period, Guido of Spoleto was refused a throne because he was an abstemious eater. Charlemagne persisted in kingly eating despite his physicians’ advice.

Pride in big meals and bodily corpulence survived the medieval demonisation of gluttony and the Renaissance cult of moderation. Louis XIV practised enlightened overindulgence. His sister-in-law often saw him “eat four bowls of different soups, a whole pheasant, a partridge, a big plateful of salad, sliced mutton in its juice with garlic, two big lumps of ham, a plateful of pastries and fruits and preserves”. Dr Johnson ate with such concentration that the veins on his forehead stood out and he broke out in sweat. Brillat-Savarin, the great early 19th-century celebrant of the philosophy of food, justified gourmandism on the grounds that it shows “implicit obedience to the commands of the Creator, who gave us the inducement of appetite, the encouragemant of savour, and the reward of pleasure”. Even today, awe for excess remains widespread outside the West. When a feast comes round, Trobriand Islanders proudly announce: “We shall eat until we vomit.” A South African saying is “We shall eat until we cannot stand”. The sheer quantity of food served and eaten persists in some societies as an indication of status.

Now, moralists, dietitians, fashion advertisers and lifestyle journalists try to nag us into frugality. I doubt whether even so formidable a combination of forces can reverse evolution and history. Gluttony has a powerful pedigree. Excess at table is hallowed by antiquity. So eat on. Face those leftovers without discouragement: you may feel bloated on Boxing Day, but your struggle with your waistband is part of an historic contest. This is the season, moreover, when supplies are abundant to sustain it and parties come to the aid of all good men.

• The author’s Food: A History is published by Pan (£7.99)

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