You can't die. You don't age. You can't get sick. But other than that, you're a normal human. If you're out of shape, you're still going to be out of shape, but you can work on yourself like usual to make yourself better. Same can be said for the other way. If you eat like shit and don't take care of yourself, you're going to be out of shape.
Which movie universe are you in now? What do you do?