Marge tries to get Homer to lose weight. But instead, he finds a support group that encourages him to embrace his largeness. The subplot is that Springfield has an anthem that every American city had dibs on it, so Bart and Lisa plan to write a new anthem.
Moe returns from a vacation in Tuscaloosa, Alabama and explains to other Springfielders in a Town Hall meeting that Tuscaloosa uses the same town anthem that Springfield, this causes a series of angry reactions. Sideshow Mel attempts to calm everyone by saying that it could be a coincidence, but Moe shows that other cities use it across the country. Austin, Oakland, Caldury, Oboe, Ulaanbaatar, and Area 51 use the same anthem. Just as the townspeople were about to riot, Mayor Quimby tells everyone that it was former mayor Hans Moleman who wrote it. Lenny and Groundskeeper Willie put Hans' hands behind his back. As the townspeople confront Hans he admits that when he was mayor of Springfield, he purchased the anthem from a salesman who was selling it to half the cities in north America, he thought no one would find out because no one from Springfield ever travels. Moleman is later tied up and sent off on a horse into the desert. Lisa explains to Mayor Quimby that she can write a new anthem. Pharrell Williams appears and offers to write a new anthem but since Lisa offered first, he is also tied up and sent off on a horse.
Lisa and Bart compose a new anthem and perform it with other Springfielders. At the performance, Homer has trouble sitting and when he stands up, he tears out his row of seats.
Marge insists that Homer joins a weight-control group, but the one Homer joins is run by Albert, an obese man who is confined to a mobility scooter. Albert teaches Homer that being fat is beautiful. Soon, Albert, Homer, and the rest of the group protest a fashion store but they are arrested.
Marge goes to bail Homer out of jail, and pleads with him to leave the group and start a diet. Homer refuses and stays. Bart and Lisa attempt to write a new song to force Homer out of the group, but their arguing prevents it.
Marge later points out that Albert can't walk, but Albert attempts to prove her wrong. However, when he gets off of his scooter, he suffers a fatal heart attack. At Albert's funeral, Homer reads his obituary and learns that Albert was only twenty-three years old. Homer then pleads for the obese to lose weight, and he turns to a yo-yo diet, which shows drastic changes to his body.