The fundamental drivers of the obesity epidemic.

Most policy makers do not yet understand that the obesity epidemic is a normal population response to the dramatic reduction in the demand for physical activity and the major changes in the food supply of countries over the last 40 years. A national focus on individual behaviour reflects a failure to confront the facts. Thus, the changes in food supply and physical environment are socioeconomically driven, and the health sector simply picks up the consequences. Urbanization alone in China has reduced daily energy expenditure by about 300-400 kcal d(-1) and cycling/bussing or going to work by car determines another variation of 200 kcal d(-1). Thus, energy demands may have dropped with additional TV/media, mechanization and computerized changes by 400-800 kcal d(-1), so weight gain and obesity are inevitable for most or all the population. Food intake should have fallen substantially despite the community's focus on the value of food after all the food crises of the past. Yet, Chinese fat and sugar intakes are escalating, and these policy-mediated features are amplified by the primeval biological drive for those commodities with specialized taste buds for fatty acids, meat, sugar and salt. Yet, traditionally, Chinese diets had negligible sugar, and 25-year-old data show that the optimum diet for Chinese contains 15% fat. Policies relating to food imports, agriculture, food quality standards, appropriate food traffic light labelling, price adjustments and controlled access to unhealthy foods are all within the grasp of the Chinese government. China has traditionally been far more responsive to the value of policies which limit inequalities and establish standards of care than many western governments, who have yet to recognize that the individualistic free-market approach to obesity prevention is guaranteed to fail. China could therefore lead the way: if it follows western approaches, the health and economic burden will become unsustainable.