Obesity and venous thrombosis: a review.

The world is experiencing an obesity pandemic, with rates of obesity rising for more than two decades. Obesity is defined as a body mass index (BMI) of 30 kg/m (2) or greater. Of particular concern are the risks that millions of obese people are likely to develop chronic diseases and at earlier ages than their parents might have. The risk of venous thrombosis increases with obesity, so that the incidence of this pathology is also expected to rise significantly. There is remarkable and consistent evidence from a systematic review, as well as cohort and case-control studies that obesity might predispose to venous thromboembolism (VTE). The risk appears to be at least double that for normal weight subjects (BMI 20 to 24.9 kg/m (2)). Plausible mechanisms exist to explain this relationship, including the physical effects of body fat limiting venous return and a proinflammatory, prothrombotic, and hypofibrinolytic milieu. Loss of body weight has been shown to reduce the concentrations of coagulation factors and plasminogen activator inhibitor-1 toward the normal range. Whether weight loss would prevent secondary occurrence of VTE in the absence of anticoagulant therapy could not be discerned from this literature search.