BACKGROUND: Obesity is known to be a multifactorial disease. In its pathogenesis, different factors such as chronic inflammation, oxidative stress, insulin resistance, genetic factors, environmental effects, vegetative disturbance, and unbalanced nutrition play a significant role. METHODOLOGY: This study describes the association of obesity and insulin resistance with chronic inflammation, genetic, and epigenetic factors. Previous literature has been reviewed to explain the relation of obesity with those factors involved in chronic low-grade inflammation and insulin. RESULTS: Obesity is associated with a decrease in ghrelin secretion, elevated plasma leptin levels, oxidative stress, increased macrophage phagocytic activity, and the induction of proinflammatory synthesis of cytokines and interferon-gamma. Obesity is linked to decreased levels of cytochrome P450 (CYP) enzymes and impaired detoxification processes. Deficiency of vitamins and minerals can also play a significant role in the development of oxidative stress and chronic inflammation in obesity. There is evidence of associations between a genetic predisposition to obesity in children with elevated levels of certain miRNAs. CONCLUSION: The purpose of the present review is an analysis of the multiple factors associated with obesity.