Professor Yudkin writes, "People don't get fat by eating the right foods." People get fat by eating the wrong foods. Overweight is especially a problem in the wealthier countries. As a result, it is assumed that people get fat when there is more food available and they can afford to buy it. But animals in their natural habitats don't get fat if there is plenty of food - more of them survive the hazards of life in the wild, and they stay thin. Care is taken in zoos to see that they are fed normal food to make sure they stay lean and healthy, and visitors are asked not to feed them with what are almost always not their normal foods. These facts form the basis of this book. John Yudkin is also the author of "The Penguin Encyclopaedia of Nutrition" and "This Slimming Business".