Book excerpt: The leading clinical reference work in the field--now significantly revised with 85% new material--this handbook has given thousands of practitioners and students a comprehensive understanding of the causes, consequences, and management of adult and childhood obesity. In concise, extensively referenced chapters from preeminent authorities, the Handbook presents foundational knowledge and reviews the state of the science of evidence-based psychosocial and lifestyle interventions as well as pharmacological and surgical treatments. It provides guidelines for conducting psychosocial and medical assessments and for developing individualized treatment plans. The effects of obesity--and of weight loss--on physical and psychological well-being are reviewed, as are strategies for helping patients maintain their weight loss. New to This Edition *Many new authors and topics; extensively revised and expanded with over 15 years of research and clinical advances, including breakthroughs in understanding the biological regulation of appetite and body weight. *Section on contributors to obesity, with new chapters on food choices, physical activity, sleep, and psychosocial and environmental factors. *Chapters on novel treatments for adults--acceptance and commitment therapy, motivational interviewing, digitally based interventions, behavioral economics, community-based programs, and nonsurgical devices. *Chapters on novel treatments for children and adolescents--school-based preventive interventions, pharmacological treatment, and bariatric surgery. *Chapters on the gut microbiome, the emerging field of obesity medicine, reimbursement for weight loss therapies, and managing co-occurring eating disorders and obesity.