Snakes are survivors and colubrids are among the best, which means they don't need a whole lot of food to maintain weight. I would suggest dropping back the mouse size to a small/large adult instead of jumbo every three weeks. Jumbos are usually older retired breeders so they're pretty high in fat.
Otherwise, exercise and lots of it. As you noted corn snakes are pretty active of their own volition so I would look into getting it a larger enclosure so it moves around more even when you aren't home to let it out.
Reply With Quote