Probably very few of them have done the serious training. Chris Froome achieved greatness in cycling through training and doping.
But the fact that of all the top non-African, non-Japanese long distance runners in the world currently at or under 60 in the half, most of them have trained for a significant amount of time in Kenya.
I count just 21 athletes with non-African heritage and excluding Japanese runners, who would add about 12 or 13 to the list, who have broken 1:01. There are 13 European athletes not of African heritage who have done so.
Of those, the guys at the top are Marilson Gomes dos Santos (59:33), Ryan Hall (59:43), Zane Robertson (59:47), Sondre Moen (59:48), Fabian Roncero (59:52), Dathan Ritzenhein and Callum Hawkins (60:00), Jake Robertson (60:01), and Julian Wanders.
Of those guys, I don't know about dos Santos. Roncero trained in the Canary Islands, running up volcanoes--so some altitude; Hall was trained and trained at altitude; the Robertsons have lived and trained in Kenya most of the last ten years or so, Wanders and Moen live in Kenya or spend large amounts of time there, and Ritz used an oxygen tent and often went to train at altitude (he trained at altitude in Europe before his great series of 12:56 AR, 27:22 in Berlin, 60:00 bronze at World half).