What is One Piece doing to keep it one chapter/episode?
The One Piece manga and anime aren't in a 1:1 ratio. The distance beetween them even shifts around. The second arc took place between the 8th and 24th chapters in the manga, while the same in the anime took place between the 4th and 8th episode.

The main reason why the anime is this slow are the fillers. They help the manga "catch a breath" and sneak in couple chapters. (side note: This is still no excuse for fillers in the middle of an arc though).

Oda likes to put in a few filler episodes after every arc or when there's a new movie out.

With these however, there's still a very big chance that the anime will eventually reach the manga. If this happens, there are 4 possibilities:


They stop airing one-piece for a year so the manga catches up.
They start airing the episodes every 2 weeks.
They do what Game of Thrones will do / did and continue with a separate story line.
They start writing the story for the anime and make the manga based on that.