The big-boned Chouji is a pupil of Asuma and a teammate of Shikamaru and Ino. Chouji spends most of his time eating, thinking about eating, and resting. He has pretty funny jutsus like the meat tank, where he triples his size and transforms himself into a huge spinning ball. And then uses his chakra to roll the ball in all directions.
He isn't really motivated to fight or do anything for that matter. The only way to get him to fight or help is to reward him with food. But when people call him chubby, fatty, etc. / mock his weight, he gets pissed off, and won't hold back. Since he's part of the Akimichi clan who specializes in body enlargement jutsu, he can also use the clan's food pills to increase his power tremendously, but that way he is putting a heavy strain on the body. Chouji is someone who is, but mustn't be underestimated.