This is a little overblown. From personal experience, 1 hour of cardio every day before work will offset an 8-hour desk shift. The biggest problem, though, is ergonomics. Sitting is hard on the body even though it's considered sedentary. It puts inordinate amounts of pressure on your lumbar and years of prolonged desk work almost always cause distortion in your discs. Muscles actually shorten over time (like the opposite of stretching every day) pulling your skeletal system out of alignment. Back problems are inevitable if you don't have absolutely perfect posture, ergonomics, and physical routine to balance you out when youre not sitting down.
There are a few things that can be done to prevent problems. 1-hour-ish exercise before work to balance your metabolism and energy levels. 10-15 minutes chilling upside-down on a teeter hang-ups after work will keep the big muscles in your thighs and back from shortening and your spine decompressed. Past that, ergonomics improvements while at work also help, the #1 being sitting at the correct height and distance from your monitor. High-end ergonomic chairs and keyboards are also worth the cost.
Speaking of which... I'm looking at getting one of these and setting it up in Dvorak format: