The mixed martial arts world is mourning the sudden death of UFC flyweight Allan Nascimento, who has died aged 34. Allan Nascimento Cause of DeathThe UFC confirmed on Monday that Allan Nascimento had died at the age of 34 after what it described as an apparent heart attack. No official autopsy findings or further details about Allan Nascimento's cause of death have been made public. Who Was Allan Nascimento? Born in São Paulo, Brazil, Allan Nascimento trained with the renowned Chute Boxe team under respected head coach Diego Lima.