Homer buys a book on world records published by Duff at a library sale. After boring everyone with world record trivia, Homer decides to break a record himself. He gathers the whole town to build the world's tallest human pyramid. After Jimbo and Kearney move their hands just before the record is claimed, the pyramid collapses into a giant sphere that rolls through town, taking in Agnes Skinner, Hans Moleman, and a suicidal man about to jump from a ledge onto the street. The entire town rolls to a truck weighing station and the Duff record book officials say that Springfield is the world's fattest town (to which Homer responds: "Take THAT, Milwaukee!")
The townsfolk are happy to have made it in the record book, but Marge is worried that the whole town is overweight. She discovers that there is sugar in nearly everything Springfielders eat, and she finds that many of its citizens are addicted to it, including Disco Stu and Dr Hibbert. After complaining to Garth Motherloving, head of the "Motherloving Sweets and Sugar Company", who acts rude and condescending to her complaints, Marge decides to sue the sugar industry with the help of Gil and Professor Frink, who reveals that the sugar companies had been using advertising to get people hooked on their products for years, similar to what the tobacco industry once did. Count Chocula also testifies, revealing that his role as a sugar mascot has cost him his fangs due to tooth decay. Despite Garth Motherloving attempting to bribe Judge Snyder, Snyder sides with Marge, heavily fining Motherloving. However, in an unexpected turn, he also bans all sugar products from Springfield, something Marge hadn't intended, which angers Homer and the rest of the town.
The whole town goes cold turkey and begins to suffer from intense sugar withdrawal, especially the children of Springfield Elementary who become delirious and begin to hallucinate. Homer joins a secret group led by Garth Motherloving to smuggle sugar from the island of San Glucos, where he obtains a large shipment of contraband sugar (for free, due to the smugglers accidentally signing a contract forgoing any payment). After arriving back in Springfield, and evading a police boat, Homer brings the sugar to the docks. Marge pleads Homer to dump the cargo. There Homer is presented with two choices: to obey Marge and press the button Drop Cargo or bring the sugar to Garth Motherloving by pressing the button Obey Bad Guy. After contemplating, Homer drops the cargo and all the sugar falls to the Springfield docks' water, and Garth leaves dejected. All Springfielders, even those who seemed happier and healthier without sugar, jump into the harbor and drink the sugar water. Judge Snyder arrives, and admits that he had grossly overstepped his judicial authority with the ban, and overturns it before jumping in to join everyone else. Marge is upset and she thinks about giving up changing the world. However, Homer tells her that he loves her when she tries to make a world a better place.