Overweight and obesity rates have been increasing relentlessly over recent decades in all industrialised countries, as well as in many lower income countries. OECD analyses of trends over time support the grim picture drawn in the international literature and so do projections of overweight and obesity rates over the next ten years. The circumstances in which people have been leading their lives over the past 20-30 years, including physical, social and economic environments, have exerted powerful influences on their overall calorie intake, on the composition of their diets and on the frequency and intensity of physical activity at work, at home and during leisure time. Many countries have been concerned not only about the pace of the increase in overweight and obesity, but also about inequalities in their distribution across social groups, particularly by socio-economic status and by ethnic background.