van der Ploeg HP, Chey T, Korda RJ, Banks E, and Bauman A (2012) Sitting Time and All-Cause Mortality Risk in 222 497 Australian Adults. Archives and  Internal Mrdicine 172(6):494-500

Prolonged sitting is considered detrimental to health. This study aimed to determine the independent relationship of sitting time with all-cause mortality. Sitting less than 8 h/d and meeting the physical activity recommendation (2.5 hours per week) protected against death. The adverse effects of prolonged sitting are thought to be mainly owing to reduced metabolic and vascular health. Prolonged sitting has been shown to disrupt metabolic function, resulting in increased plasma triglyceride levels, decreased levels of high-density lipoprotein cholesterol, and decreased insulin sensitivity, which appear to be at least partially mediated by changes in lipoprotein lipase activity. It has also been suggested that sedentary behaviour affects carbohydrate metabolism through changes in muscle glucose transporter protein content.