Robin Hood's companion Friar Tuck had hundreds of real-life counterparts, according to a newly published analysis of skeletons in three monastic burial sites in London.

Suet, lard and butter were wolfed down in "startling quantities" by the closed communities, whose abbots often depended on arranging large and regular helpings to keep their flocks under control.

"The way to a man's heart is through his stomach and this seems specially to have been the case with monks," said Philippa Patrick, of the Institute of Archaeology, at University College, London. "They were taking in about 6,000 calories a day, and 4,500 even when they were fasting."

Arthritis in knees, hips and fingertips showed that the often under-employed monks were seriously obese.

Ms Patrick, whose findings were revealed to the International Medieval Congress, meeting in Leeds, said: "Their meals were full of saturated fats. They were five times more likely to suffer from obesity than their secular contemporaries, including wealthy merchants or courtiers."

The reckless scoffing was in clear breach of St Benedict's austere rules laid down probably in 530, which warned: "There must be no danger of overeating, so that no monk is overtaken by indigestion, for there is nothing so opposed to Christian life as overeating."

Critics, such as Peter the Venerable, who slated monks for "wearing furs and eating fat", were advised however that Benedict had also warned about grumbling: "Brethren would indeed grumble if deprived of the food to which they are accustomed."

The skeletal data, from 300 sets of bones found at Tower Hill, Bermondsey, and Merton abbeys, includes information on a medical condition known now as Dish (diffuse idiopathic skeletal hyperostosis) triggered by overeating and a rich diet. "The marks of Dish keep appearing on their skeletons. It forms a coating on the spine like candlewax dripping down the side," said Ms Patrick.

The findings tally with satire that developed a keener edge after the Black Death and food shortages. Friar Tuck was only one of many fat fictional characters based on medieval churchmen by resentful lay storytellers.

The new evidence backs records from Westminster Abbey, showing that six eggs a day was normal for monks. In the middle ages, monkish obesity was Europe-wide. The Portuguese Cistercians had a test: monks unable to squeeze through a certain doorway at Alcobaca monastery's dining room had to fast while slimmer colleagues tucked into "pastry in vast abundance".

Friar's tucker

A 13th century Cluniac friar's possible daily intake based on Ms Patrick's studies:

11am-1pm Three eggs, boiled or fried in lard. Vegetable porridge with beans, leeks, carrots and other produce of monastery garden. Pork chops, bacon, and mutton. Capon, duck and goose with oranges. Half pound of bread, to use as sop. Peaches, strawberries and bilberries with egg flan. Four pints of small (watery) beer.

4-6pm Mutton gruel with garlic and onions. Posset of egg, milk and figs. Venison with rowanberries, figs, sloes, hazelnuts and apple. Stewed eels, herring, pike, dolphin, lamphreys, salmon, cod and trout. Half pound of bread as sop, sometimes soaked in dripping or lard. Syllabubs of fruit. Four pints of ale. Flagon of sack or other French, Spanish or Portuguese wine.