Obesity is a major contributor to metabolic syndrome, and this study shows that increased oxidative stress in fat tissue is a key mechanism. In both humans and mice, fat accumulation is linked to systemic oxidative stress, with elevated ROS production in adipose tissue. This leads to dysregulated adipocytokine production, including adiponectin, PAI-1, IL-6, and MCP-1, which contribute to insulin resistance and metabolic syndrome. NADPH oxidase activity increases in adipose tissue of obese mice, while antioxidant enzymes decrease, worsening oxidative stress. Inhibiting NADPH oxidase with apocynin reduces ROS, improves adipocytokine regulation, and alleviates diabetes, hyperlipidemia, and hepatic steatosis in obese mice. These findings suggest that oxidative stress in fat tissue is an early driver of metabolic syndrome and a potential therapeutic target. The study highlights the role of oxidative stress in the pathogenesis of obesity-related metabolic syndrome and supports the use of NADPH oxidase inhibitors as a treatment strategy.Obesity is a major contributor to metabolic syndrome, and this study shows that increased oxidative stress in fat tissue is a key mechanism. In both humans and mice, fat accumulation is linked to systemic oxidative stress, with elevated ROS production in adipose tissue. This leads to dysregulated adipocytokine production, including adiponectin, PAI-1, IL-6, and MCP-1, which contribute to insulin resistance and metabolic syndrome. NADPH oxidase activity increases in adipose tissue of obese mice, while antioxidant enzymes decrease, worsening oxidative stress. Inhibiting NADPH oxidase with apocynin reduces ROS, improves adipocytokine regulation, and alleviates diabetes, hyperlipidemia, and hepatic steatosis in obese mice. These findings suggest that oxidative stress in fat tissue is an early driver of metabolic syndrome and a potential therapeutic target. The study highlights the role of oxidative stress in the pathogenesis of obesity-related metabolic syndrome and supports the use of NADPH oxidase inhibitors as a treatment strategy.