The Guinness World Records organisation has recognised Yisrael Kristal, a Polish Jew born in 1903, as the world's oldest man. Kristal, a survivor of several camps, lost children and his wife during the Holocaust. When eventually liberated by the Aliies, he weighed just 37 kg (5.8 stone).
Further details below courtesy of the BBC website:
Auschwitz survivor is world's oldest man - Guinness World Records - BBC News