NoNo, just because you don't have to leave your desk doesn't mean you shouldn't leave your desk--you should! Get up every hour, walk around, have a glass of water. That and what NbyNW said. You are young, and you have the opportunity to change your habits so you won't end up with chronic back pain down the road.

I learned from my dog trainer, of all people, to walk and sit and stand like a dancer or like Queen Elizabeth. I put that in my head, and it's slowly becoming a good habit. Driving is the hardest for me--Queen Elizabeth didn't drive! Luckily I don't have to drive often--once a week or so to the grocery store. But once a month I have to take long driving trips for work. I really have to focus, and I also get out of the car every 2 hours. Otherwise my hip complains loudly!

Pilates really helps with butts, too. If you want a nice butt, do Pilates. Done right, it really helps with just about everything, particularly if you take what you learn in the class and apply it to your being everyday and everywhere.