Obesity: the disease of the twenty-first century.

The prevalence of obesity is increasing globally, with nearly half a billion of the world's population now considered to be overweight or obese. The obesity epidemic is related both to dietary factors and to an increasingly sedentary lifestyle. Obesity has significant co-morbidities and these are associated with substantial health care and social costs. Of particular concern is the fact that obesity is increasing among children and adolescents. National health policymakers must take action to deal with the obesity problem. Prevention should be the primary target, but it is also important to develop strategies to treat those already affected with obesity.