As each of the Lil' Leatherfaces is whisked away by the cold hands of death, the unwaveringly jovial voice of the narrator makes sure that any children watching understand two things:
First: There are some basic rules of the road for cyclists that everybody should follow.
Second: You are naught but animals to adults, and they will not care if you die in terror and pain.
Like this guy, whom the narrator explicitly tells you is "a really nice boy," approximately two seconds before the movie flashes us his gruesome pre-death face and he gets mowed down by an automobile like an unlucky squirrel.
Show, not tell, Mr Narrator.
One by one, the monkey-kids are systematically destroyed for their mistakes until there is only a single survivor. This Bicycle Highlander's name is Orville, and it's revealed that not only is he the sole survivor of this harmless bike trip, but he's also the only human being. But instead of mourning his simian friends, he calmly sits down at the park all alone, to eat all of their lunches.
Understand the title now? No?
Here, we'll explain: The "one" refers to Orville, the winner of this interspecies death race, and he "got fat" by seizing the lunches of his fallen friends like trophies and callously devouring them. Or, to put it another way: "To the victor go the spoils."
See that? That's the thousand-yard stare of a boy who looked into the face of death and then ate its friggin' Lunchables.