Does eating more carbohydrates, or fats, cause one to put on more weight? Are ketone bodies toxins or vital products that keep us alive during starvation? Does the concept of 'fat-burning exercise' hold true? In this game-changing book, Keith Frayn, an international expert in human metabolism and nutrition, dispels common misconceptions about human metabolism, explaining in everyday language the important metabolic processes that underlie all aspects of our daily lives. Frayn describes the communication systems that enable our different organs and tissues to cooperate, for instance in providing fuel to our muscles when we exercise, and in preserving our tissues during fasting. He explores the impressive adaptability of human metabolism and discusses the metabolic disorders that can arise when metabolism 'goes wrong'. For anyone skeptical of information about diet and lifestyle, this concise book guides the listener through what metabolism really involves.