“Several factors could explain the positive association between time spent sitting and higher all-cause death rates,”. “Prolonged time spent sitting, independent of physical activity, has been shown to have important metabolic consequences, and may influence things like triglycerides, high density lipoprotein, cholesterol, fasting plasma glucose, resting blood pressure, and leptin, which are biomarkers of obesity and cardiovascular and other chronic diseases.” 

Alpa Patel, Ph.D (The doctor who was one of the researchers who led the exploration to the association between sitting time and mortality analyzed survey in the American Cancer Society’s Cancer Prevention II study in 1992.