30 years ago the town mayor, Hans Moleman, wrote an anthem for Springfield. 

Moe comes running into a town meeting and announces that other towns have the same song. Lisa volunteers to write a new song and Pharrell Williams shows up to offer as well, but Mayor Quimby already gave it to Lisa. 

Lisa enlists Bart's help in writing the song and the two of them perform it in front of the town. Everyone loves the song and gives them a standing ovation. Homer gets stuck in his seat and causes damage and injuries. Marge sends him to overeaters anonymous, but Homer wanders into a meeting for big is beautiful instead. 

Homer returns home and tells Marge that he met a man named Albert who taught him to be proud of his weight. Homer goes to Moe's and reads a long list of weight related insults his friends aren't allowed to call him anymore. 

Homer joins a movement with the group and gets arrested. Marge bails him out and tells him has to choose. Homer chooses to go back in the jail cell with the others. 

Marge returns home alone and depressed. Bart tells her that he and Lisa will write a song to make Homer change his mind. 

Lisa and Bart admit that they couldn't write a second song and are one-hit wonders. Marge and Homer argue about Homer following a man who wouldn't even get out of his chair. Albert stands up and dies of a heart attack. Homer realizes Marge was right and promises to keep yo-yo dieting until he gets it right.