Mayo Clinic Reports:
Research has linked sitting for long periods of time with a number of health concerns, including obesity and metabolic syndrome — a cluster of conditions that includes increased blood pressure, high blood sugar, excess body fat around the waist and abnormal cholesterol levels. Too much sitting also seems to increase the risk of death from cardiovascular disease and cancer.
http://www.mayoclinic.org/healthy-lifestyle/adult-health/expert-answers/sitting/faq-20058005