Because he used to be an astronaut with an unusually large mouth/gullet.
He was out one day having space adventures, when he saw a comet coming toward Earth (approximately the size of Belgium). Terrified, he sent dozens of emails from his smartphone, but every member of NASA had the day off and weren't checking their mail. He then turned around and saw the comet was only 50 feet from him! He gasped and opened his mouth (approximately the size of Germany) and the comet flew right in.
It flooded his entire body with spacial rubble, and when he vomited it all out in the ER, it had stretched out his stomach and limbs.
And that is the story of the tragic obeseness of King Zora.