A large number of children's weight are more and more heavier, which trend is becoming obvious. This phenomenon is mainly based on the two reasons below. With the development of the living standard of the people, children have more chances to have dinner outside. They can't push against temptation of McDonald、KFC or Pizza Hut. These fast food companies spend millions of dollars on the ads which focus on children. However, these ads make great profit for these companies. Children always patronize fast food chain stores. As a result, they become fatter. The second reason is that kids lack of excrises. Nowadays, kids are busy with studying and someone even stays at home all day. It is the increase of ingesting calorie and the decrease of sport time that lead children to be in danger of being fat. Gernally speaking, there is no doubt that we should pay more attention to the problem of children. We should also promote a big activity that is opposed to the western fast food coming into China.