Such obesity-related diseases were once unheard of in China but about 20 million people now have diabetes, while an equal number have impaired glucose tolerance, a pre-diabetic condition, Xinhua news agency said.
"Many Chinese eat more and exercise less, which is the main reason why the number of diabetes patients... is growing fast," said Qi Xiaoqiu, director of the ministry's disease control and prevention department.
At a function to mark World Diabetes Day, Qi called the disease a "serious health problem in China."
According to ministry figures 12 percent of children in China's big cities are overweight, Xinhua said.
Yang Wenying, director of the diabetes branch of the Chinese Medical Association, advised parents to limit their children's intake of fast food, snacks and soft drinks and the time they spend watching TV and playing computer games.
China said last year that 60 million people -- roughly the population of France -- were classified as obese.