'Are you interested in your health and want to understand how your body functions? Do you want to learn the science behind how food and exercise interact and how together they can both foster wellbeing or lead to poor health and disease? This, and all you need to know about the key role of human metabolism for health and disease, is what Understanding Human Metabolism gives you. The author, Professor Keith Frayn, is probably the best teacher of human metabolism and nutrition of our times and has published several superb books on the topic for students of medicine and nutrition. This time, I would like to congratulate anyone without medical training but with an interest in human metabolism - this is the book for you.' Olle Ljungqvist, Professor of Surgery, Örebro University and Affiliated Professor of Surgery, Nutrition and Metabolism, Karolinska Institute, Sweden