SELECT CONCAT(usrFirstname,'',usrSurname) As FullName, usrNickname AS Nickname, usrEmail As EmailAddress, CASE WHEN usrGender = 0 THEN 'M' ELSE 'F' END AS Gender, DATE_FORMAT(usrDOB,'%d%m%y') As DOB,usrBelt AS BeltId FROM user

se você colocar isso na consulta, ele retornará M ou F