Venous thromboembolism (VTE), deep vein thrombosis (DVT) or pulmonary embolism (PE) is a common medical condition encountered during hospitalization in a medical environment. The use of thromboprophylaxis with Low Molecular Weight Heparin (LMWH) or fondaparinux has reduced more than 50% relative risk of thromboembolic complications.However, while obesity defined by a body mass index (BMI) greater than 30 kg/m2, is a major risk factor for venous thrombotic events, data on obese patients are limited. In fact, less than 20% of patients included in the three major studies of preventive medicine had a BMI ≥ 30 kg/m2 and most studies specific to the obese population comes from a series of bariatric surgery patients or orthopedic surgery. The main results of this series show regarding the obese population a decrease of the anti-Xa activity during the administration of a standard dose of enoxaparin (40 mg / d). However, no specific recommendation in this population has not been published to date and therefore,the dosages currently used are the same regardless of the patient's weight. In this context, the use in obese patients hospitalized in a medical environment a stronger dosage of enoxaparin (60 mg / d) compared to the standard dose of 40 mg / day, could get rates anti-Xa activity levels more consistent with the treatment required, and thus reduce the risk for thromboembolic complications in these patients