As widely spread health problems related to over- and undernutrition have grown nowadays to an epidemic extent and even prevail over infectious diseases, a better knowledge of the metabolic basis of clinical nutrition has become essential. The extremes of the nutritional spectrum, undernutrition and obesity, are no longer considered as isolated opposites with different effects on separate risk groups, but paradoxically prove to be interacting in a setting of rapidly changing lifestyles, as is presently the case worldwide. Recurring issues such as insulin resistance, changes in intermediary metabolism, fluid and electrolyte physiology, genetic and non-genetic inheritance are highlighted, as well as the biological linkage between maternal undernutrition and the development of obesity, diabetes and cardiovascular disease in later life. The problems at stake present a new and enormous challenge for future healthcare policies and, therefore, are better tackled today. This book will be an interesting source of knowledge for internists, family physicians, pediatricians, dieticians, endocrinologists, gastroenterologists, and public health officers.