The film tells the story of four friends who gather in a villa for the weekend with the express purpose of eating themselves to death. Bouffer is French slang for "eating" (the Italian abbuffata means "great eating").
The first protagonist, Ugo, owner and chef of a restaurant, "The Biscuit Soup", decides to commit suicide, probably because of misunderstandings with his wife. The second is Philippe, a somewhat important magistrate who still lives with his childhood nanny, Nicole, who is overprotective of him to the point of trying to prevent him from having relationships with other women, and who fulfills her own sexual needs with the judge. The third character is Marcello, an Alitalia pilot and womaniser, who is devastated by the fact that he has become impotent. In the first scenes in which he appears, he is intent on making one of his air-hostesses carry off the plane an entire Parmigiano for the villa where he will meet up with the other three protagonists. The fourth and final main character is Michel, who is an effeminate television producer, divorced and tired of his monotonous life. The four come together by car to the beautifully furnished but unused villa owned by Philippe. There they find the old caretaker, Hector, who has innocently prepared everything for the great feast, and a Chinese visitor who is there to offer a job to the magistrate in faraway China, which Philippe politely rejects with the phrase "Timeo Danaos et dona ferentes", quoting Virgil.
Once alone, the four begin their binge. In one scene Marcello and Ugo race each other to see who can eat oysters faster. They discuss organizing a little "feminine presence" and decide to invite three prostitutes (not four because Philippe does not want to participate) to come to the house the following evening. Their breakfast next day is interrupted by the arrival of a school class who would like to visit the garden of the villa to see the famous "lime-tree of Boileau", a tree under which the French poet used to sit while looking for inspiration. The four willingly invite the class not only into the garden but also to view the old Bugatti in the garage and to a magnificent lunch in the kitchen. Above all, they get to know Andrea, the young and buxom teacher, whom they spontaneously invite to dinner that evening. Philippe is dismayed at the notion of the school teacher being in the same company as three prostitutes; he warns her but she appears not to be perturbed. The prostitutes arrive in due course and the atmosphere becomes frivolous and sexually charged. Andrea arrives and embraces the spirit of the party. She is attracted to Philippe, who proposes to marry her.
The eating continues unabated. Ugo is responsible for the preparation of the food. Michel, who seems to have been brought up strictly not to fart, suffers from indigestion. His friends encourage him to let go and fart.
Frightened by the turn of events, the prostitutes flee at dawn and leave only Andrea. She seems to sense the purpose of the protagonists and decides to help them in their efforts, establishing a tacit agreement and remaining with them until the death of all four.
The first to die is Marcello, after being enraged with his own impotence; he goes to the toilet and causes the sanitary pipes to explode. The house is flooded with excrement. He becomes exasperated and realizing the futility of the farce, decides to leave the house at night during a snow storm in the old Bugatti that he had repaired earlier in the day with great delight. His friends find him the next morning, frozen in the driving seat. The first suggestion is to bury Marcello in the garden, but on the advice of Philippe (who, being a judge, warns that there is a severe penalty for the illegal burying of a corpse) they place the body in the villa's cold room, where it remains seated and clearly visible from the kitchen.
After Marcello comes Michel, who already suffering from indigestion and crammed to capacity with food (he cannot even lift his legs practising dance, his favourite pastime) suffers an attack of bowel movements while playing the piano. Amid flatulence and worse he collapses on the terrace. His friends place him in the cold room next to Marcello.
Shortly afterwards, Ugo prepares an enormous dish made from three different types of liver pâté in the shape of the Dome of St. Peter, which he serves to the remaining diners, Philippe and Andrea, in the kitchen in view of the two dead friends. Philippe and Andrea cannot bring themselves to eat it however. Philippe goes off to bed leaving Andrea to keep Ugo company during his determined effort to eat the entire pâté. Some time later she later calls Philippe back downstairs to help her stop his friend from stuffing himself to death. They cannot dissuade Ugo however, and end up attending to him on the kitchen table, the one feeding him, the other masturbating him until he dies. On the advice of Andrea, his body is left on the kitchen table, in his "domain."
Last to die is the diabetic Philippe on the bench under the lime-tree of Boileau and into the arms of Andrea after eating a cake she has made shaped like a pair of breasts. He dies just as another delivery of meat arrives. The delivery men react with incomprehension when Andrea instructs them to leave the meat - whole animals and sides of pork and beef - in the garden (the cold room being full). The film ends bizarrely with a scene of the garden filled with neighbourhood dogs, geese and poultry, and meat carcasses.
Marco Ferreri won the FIPRESCI Prize given by the International Federation of Film Critics at the 1973 Cannes Film Festival. It was later shown as part of the Cannes Classics section of the 2013 Cannes Film Festival.
The film was somewhat controversial upon its original release with its scatological humour and comic depictions of sex and over-eating.