Akamu wasn't always chunky. In fact, such corpulence is normally looked down upon from fighters in Krom as a sign of weakness. Akamu was a gladiator from a young age and, seeing how larger fighters tended to win and rewards tend to include more and high quality food, his young mind put largeness and thickness as being strong and successful.
He feels guilty about it, but he truly enjoys being a tubby guy.
Credit goes to oreocakes