Japanese centenarian Jiroemon Kimura, the oldest man in the world, is celebrating his 116th birthday.Mr Kimura, from Kyotango in Kyoto Prefecture, who was born in 1897, was already the oldest recorded human to have ever lived before Friday's celebrations.To mark his 116th birthday, Mr Kimura, who lives with his family, received a birthday video message from Shinzo Abe, the Japanese prime minister.The former postman modestly attributes his longevity to a life of moderation, including the avoidance of smoking and eating until he is only 80 per cent full.Mr Kimura, who has 25 great grandchildren and 13 great great grandchildren, reportedly lives by the motto "to eat light and live long".Meanwhile, the pensioner's long and healthy life has prompted officials in his hometown Kyotango to launch a study into the causes of such longevity.