Obesity is defined as the state of having a body mass index (BMI) greater than 30. Although it may be easy to identify what obesity is, however, identifying its causes and effects can be more challenging. Genetic, hormonal, environmental, and behavioral factors all play a role in defining our weight, and the consequences of obesity go far beyond medical complications, to include impacts on psychological well-being and social health, and how we think about and address this growing epidemic has become just as controversial as it is important. This second edition offers a wealth of new information and features. Coverage of genetic and hormonal causes of obesity has been greatly expanded, as has discussion of medications and surgical techniques to manage obesity. The book reflects our expanded scientific understanding of obesity and delves into medical and societal debates about weight that have emerged in recent years. Also new in this edition is a collection of case studies, each of which helps to make the topics discussed in the book more accessible to readers.