[QUOTE=Neckhammer;1164294]^Its not simply correlation. Look at biomechanical studies of load and force on the spine in different postures and you can begin to appreciate why that extended time in a standard western seated position creates problems with joint and disc function and subsequently neurological feedback. [/QUOTE]
I thought there were some pretty conclusive trials showing a decrease in the production of lipoprotein lipase (the enzyme that frees fat from the adipose tissue) after prolonged sitting as well, but I don't have a cite handy.
And sitting isn't just bad in that it's such a sedentary behavior, it really messes with your flexibility/mobility. Most people who sit 5+ hours a day are the ones who can hardly do exercises like Back/Front/Overhead Squats, Snatch, Clean/Jerk, Etc. It's just a dumb idea if you had the choice to stand. I am still in high school so I use a foam roller to help thoracic extension and hip mobility every day when I get home from school and right before I work out. I can feel a biiiiiggg change in flexibility and actually (due to the thoracic extension part) my posture and breathing just after about 2 months.