Obesity represents a serious nutritional problem worldwide, as it dramatically increased during the past 20 years. It is often accompanied by an increased risk of mortality and morbidity and, in the case of non-fatal health problems, the quality of life is impaired. Recently, it has been proposed that unbalanced redox state may be the mechanism linking obesity and the associated complications; indeed, obesity may be viewed as a state of chronic oxidative stress, characterized by enhanced levels of reactive oxygen or nitrogen species (ROS/RNS) and impaired antioxidant defences. In this chapter, we will review current concepts in the meaning of oxidative stress in obesity and the potential interventions to improve the body antioxidant machinery.