"The American Cancer Society examined leisure time
spent sitting and physical activity in relation to mortality.7
It found the risk for women with ≥ six hours/day sitting
during the time period studied had a 40 percent greater
risk to die than those with ≤ three hours a day sitting.
For men, the increased risk was somewhat less, but still,
men with ≥ six hours spent sitting had a 20 percent
greater risk for mortality than those with three or less
hours. Associations were strongest for cardiovascular
disease mortality. The study involved 53,450 men
and 69,776 women during a 14-year follow-up study
adjusting for smoking, body mass index and other
factors. In a nutshell: reduced time sitting has a beneficial
impact on mortality."
http://www.nytimes.com/2011/04/17/magazine/mag-17sitting-t.html?_r=1
Don't over do it and take some breaks. Work smarter and try to outsource a big part of your work (if you can)