Book excerpt: This book summarizes the effects of obesity on health and its correlation with a wide range of debilitating and life-threatening conditions in humans. It discusses the possible pathological mechanisms that are involved in the development of obesity and highlights obesity-associated molecular mechanisms that contribute to reproductive dysfunctions in men and women. The book provides mechanistic insights on the role of obesity in cardiovascular and respiratory disorders, and examines the role of the complementary molecular mechanism of the gut microbiota in the development of obesity. It also reviews the interaction between the metabolic system and immune cells in the pathogenesis of obesity-associated diseases. Lastly, it assesses the latest advances in nanomedicine as an emerging strategy for the treatment of obesity.