Over the last decade, the prevalence of obesity in Western and Westernizing countries has more than doubled. A standardized classification of overweight and obesity, based on the body mass index now allows a comparison of prevalence rates worldwide for the first time. In children, the International Obesity Taskforce age, sex, and BMI specific cut-off points are increasingly being used. BMI data are being evaluated as part of a new analysis of the Global Burden of Disease. Prevalence rates for overweight and obese people are very different in each region with the Middle East, Central and Eastern Europe and North American having higher prevalence rates. Obesity is usually now associated with poverty even in developing countries. Relatively new data suggest that abdominal obesity in adults, with its associated enhanced morbidity, occurs particularly in those who had lower birth weights and early childhood stunting.