This book provides a thorough source of information on the methods used to study protein metabolism in humans, and what we have learned by using these methods. The book focuses on understanding the principles of the methods, and on their limitations. It discusses the basic concepts and mechanisms of protein dynamics and turnover, nutritional influences and the regulation of the process by hormones and by general metabolic regulation. A chapter covers the role of physical activity in modulating protein metabolism. Clinical aspects, such as diabetes, obesity, anorexia and malnutrition are also included.