In this Very Short Introduction, David Bender explains the basic elements of food, the balance between energy intake and exercise, the problems of over- and under-nutrition, and raises questions on the safety of nutritional supplements. Looking broadly at what constitutes nutrition, Bender provides insight into a topic of wide interest and importance in today's world. With a look at diet in relation to nutrition, this Very Short Introduction provides an overview of the biochemistry of nutrition and the health risks associated with poor nutrition- including obesity and types of food allergies. It provides an essential guide to effectively understand the principles of, and necessary reasons for, a healthy diet.