Book excerpt: Children's health has made tremendous strides over the past century. In general, life expectancy has increased by more than thirty years since 1900 and much of this improvement is due to the reduction of infant and early childhood mortality. Given this trajectory toward a healthier childhood, we begin the 21st-century with a shocking developmentâ€"an epidemic of obesity in children and youth. The increased number of obese children throughout the U.S. during the past 25 years has led policymakers to rank it as one of the most critical public health threats of the 21st-century. Preventing Childhood Obesity provides a broad-based examination of the nature, extent, and consequences of obesity in U.S. children and youth, including the social, environmental, medical, and dietary factors responsible for its increased prevalence. The book also offers a prevention-oriented action plan that identifies the most promising array of short-term and longer-term interventions, as well as recommendations for the roles and responsibilities of numerous stakeholders in various sectors of society to reduce its future occurrence. Preventing Childhood Obesity explores the underlying causes of this serious health problem and the actions needed to initiate, support, and sustain the societal and lifestyle changes that can reverse the trend among our children and youth.