Obesity has become more prevalent throughout the world in all age groups. Obesity is a flag for (and often a precondition for) various important chronic diseases. Avoiding obesity may help a person to avoid various chronic diseases; preventing obesity is a better option than trying to control it. As a society, we need to focus on how to prevent obesity in children and adults. Obesity needs to be treated in order to prevent comorbid conditions from developing and to manage them better if present. The social and psychological aspects of obesity cannot be ignored, especially in connection with preventing childhood obesity. These are important issues for most obese adults as well (with a need to prevent discrimination, stigmatization, ridicule, and loss of willpower). Research relating to epidemiology, physiological mechanisms for controlling body weight, the pathophysiology of obesity, and treatment can lead to advances in the management of obesity throughout the world.