HONG KONG/SHANGHAI, China — As China builds fewer houses and bridges, its consumers buy cheaper, less healthy meals, and as factories and farms invest in automation, a new fiscal challenge is emerging: the country's obesity rate may grow much faster and add to health care costs.

Job stress, long work hours and poor diets are growing high-risk factors in the cities, while in rural areas, agriculture work is becoming less physically demanding and inadequate health care is leading to poor screening and treatment of weight problems, doctors and academics say.