Oda likes his juxtapositions. Eating is one of Luffy's defining traits, along with his love of food and parties. I'm guessing Oda will make Imu detest food, seeing it as a weakness, something that peasants and commoners indulge in out of need and pleasure. He's an immortal with a God complex, so why would he share in that very human tradition? A table of food is a place where people connect with one another, through banquets, feasts, and get togethers. Imu, the misanthrope he is, would never participate in such ceremonies. After all, an immortal like himself needs no fuel, and he takes pride in that separation.