Chouji fighting you over food? Okay, as realistic as this may be... with all the free food there, as greedy as Chouji might be, I don't think he would really want to fight over it, as long as he has food in his mouth. How about...
"Uh oh! You and Chouji both grab a bag at the same time! You try to free it from his grasp, but his hunger is too much for you, and he pushes you to the ground, walking away snickering while eating the food."
That sounds more reasonable than him fighting you.