Twenty-five years after China opened up to the west the Chinese are paying a price. Rapid social and economic change is transforming China, with enormous implications for its population and economy. Today the country has the fastest-growing obesity rate in the world and more than a fifth of China’s adult population is overweight, related to changing dietary and physical activity patterns. Overweight and poor diets are becoming a greater burden for the poor than for the rich, with subsequent large increases in hypertension, stroke, and adult-onset diabetes. The related economic costs represent 4–8 percent of the economy.