Theologian Massimo Salani condemned burgers in the Italian bishops' daily Avvenire, saying they were "not Catholic."
"At McDonald's people want a fast meal and hunger is quenched as fast as possible, so one can do something else, and one loses the value of community," argued Salani, author of a book called "A tavola con le religioni" (Sitting Down With the Religions).
Eating burgers and fries reflected an "individualistic relationship between man and God which goes back to [Martin] Luther," the Protestant leader who started the German Reformation.
Stung by the criticim, McDonald's Italy reacted bluntly.
"Fast food means that one is served rapidly and not that one eats rapidly," said a company statement.
The debate also drew ironic comments by politicians and newspapers, which defended the Italian variety of fast food -- pizza -- but admitted that U.S.-style fast food was cheap compared with most other Italian meals.
McDonald's said it was serving hamburgers "to customers of all races and religions and we adapt to all cultures and tastes."
That, it said, was why kosher burgers were being served in Israel and no beef was being offered in India where cows are considered sacred.
Salani said religions and Christians were ultimately responsible for the triumph of fast food throughout the world.
"Food is a gift of God and the purity of the creation can only be a common challenge for believers," he added.
But Salani not only took Protestants to task for eating badly and fast but also criticized Catholics for eating too much and Muslims for having an unbalanced diet.
"There is nothing better than Christians' free access to food, from a theological and dietary point of view," he added.
Scoffing at Salani's article, the newspaper La Stampa said it was easy to criticize eating habits but recalled that "many people don't eat at all."
"The Church should take care of these people," said La Stampa, rather than worrying about fast food, "which only leads to feeding more mouths." Communist party leader Fausto Bertinotti, not known to be a friend of globalization but once in a while tempted by the odd burger, said that "hamburgers are not the enemy, or Satan. They're just not my idea of civilization."