
He, who came 45th at the August world championships in Budapest, was neck and neck with North Korea’s Han Ilryong at the 40km mark of the Qiantang River Green Belt course.
But he gradually ground down the 23-year-old to edge clear and power to the finish line in 2 hours 13 minutes 2 seconds, 25 seconds ahead.
China’s Yang Shaohui did just enough to earn bronze ahead of Japan’s Toshiki Sadakata.
In contrast Chumba, who won the Rotterdam marathon this year, was in a class of her own, winning by nearly two minutes in 2 hours 26 minutes 14 seconds.
China’s Zhang Deshun came second ahead of Kyrgyzstan’s Sardana Trofimova.