I've had that issue. I spend a lot of time at a desk now, but I also get up and walk around a lot and when I have to go to another floor in the building I use the stairs instead of elevator. Also, I park as far away as I can (depending on the time/weather/parking availability) so I get a little exercise walking to and from work. Another downside about working at a desk is that I tend to snack a lot and my office sucks because people are always bringing snacks (mostly unhealthy) in. And the vending machines have mostly unhealthy snacks/drinks. I try as much as I can to bring in my own healthier snacks/drinks and to resist having what's there.