Over the last two decades, obesity has reached epidemic proportions in the world, resulting in suffering and premature death. Morbid obesity is a chronic medical illness that has long-reaching consequences and is caused by multiple factors. Bariatric surgery and other non-invasive procedures in carefully selected patients are effective treatments for obesity. It is the only tool for sustained and effective long-term weight loss.The field of surgery is developing rapidly -- offering innovative options for patients who have failed to lose weight by diet, exercise and pharmacological methods. The editors review problems that the patients face in the perioperative period and in the long term, as well as their adjustments in lifestyle and healthcare management.The text is authored by authorities who participate in the multidisciplinary care of bariatric patients. It will address the assessment and selection of patients' treatment before surgery, options for surgical intervention and postoperative medical management.