 Losert was born in Zavidovići, SR Bosnia and Herzegovina, grew up in Slavonski Brod, SR Croatia.Winning the first medal at the age of 19 at 1996 Summer Olympics in Atlanta, when Croatia won the first gold medal as an independent nation, he is considered the youngest debutant of the team.Losert was also the member of the golden national handball team that won the first place at the 2004 Summer Olympics in Athens.