Cellular and molecular studies have revealed that obesity generates oxidative stress by mechanisms including hyperglycemia, elevated tissue-lipid levels, inadequate antioxidant defenses, chronic inflammation, excessive leukocyte infiltration and activation, endothelial ROS production, excessive renin-angiotensin system (RAS) hormone production, and hyperleptinemia. This evidence concerns the gene REN and obesity due to melanocortin 4 receptor deficiency.