A Japanese man who received his certificate as the world's oldest man earlier this month has died aged 112. Guinness World Records had given the certificate to Chitetsu Watanabe on February 12. The cause of has not been revealed. Watanabe had not been able to eat recently and developed a fever and difficulty breathing a couple of days before his death, Japan's nationally circulated newspaper Mainichi reported, citing family sources. Watanabe was born in 1907 and worked in Taiwan for 18 years. He said the secret to longevity was to keep smiling.