This book explores the complex relationship between physical activity, inflammation, and various psychological functions of the brain such as depression, anxiety, stress, and personality. It discusses the role of the immune system in regulating inflammation and how chronic inflammation can lead to various health problems such as cardiovascular disease, diabetes, and cancer. The book also delves into the immune-cytokine paradigm of depression, which suggests that inflammation plays a crucial role in the development of depression. It explains how cytokines, which are signaling molecules produced by the immune system, can affect the brain and lead to changes in mood, behavior, and cognition. Furthermore, the book examines the impact of physical activity on inflammation and psychological well-being. It discusses how exercise can reduce inflammation in the body and improve mood, cognitive function, and overall quality of life. It also explores the potential mechanisms underlying the beneficial effects of exercise, such as the release of anti-inflammatory cytokines and the activation of the brain's reward system.