Endurance athletes train for hours per day. Skill athletes spend hours per day doing what we call "exercise" but which they think of as low-intensity skill work, separate from their physical training. But even then, their physiques are a reflection of professionalism. Look at the NFL: the linemen must burn more calories than the receivers, but the linemen are chubby and the receivers are lean. So while they're all eating a lot compared to a regular person, they're not eating some random huge amount; they're eating the right diet to support the physique they need for competition, with the support of doctors and nutritional professionals.