What is the topic of the news?

A research showed China faced a big challenge to fight rising obesity. The increasing use of vehicles was among the main causes of the increase in obesity worldwide and in China, said Professor Philip James, president of the International Association for the Study of Obesity. He suggested China should build more rail links like those from Beijing to Shanghai. Meanwhile, the popularization of British and American food in China worsened the situation, said James. Obesity is not only a social problem, but also an economic one, he said, adding the World Health Organization predicted China’s economic growth would be slowed by falling health levels among the people.