 Obesity has long been regarded as a risk factor for venous thrombosis . It more than doubles the risk in numerous studies , particularly in combination with the use of oral contraceptives or in the period after surgery . Various coagulation abnormalities have been described in the obese . <unk> activator inhibitor @-@ 1 , an inhibitor of fibrinolysis , is present in higher levels in people with obesity . Obese people also have larger numbers of circulating <unk> ( fragments of damaged cells ) that bear tissue factor . <unk> aggregation may be increased , and there are higher levels of coagulation proteins such as von Willebrand factor , fibrinogen , factor VII and factor VIII . Obesity also increases the risk of recurrence after an initial episode of thrombosis . 
