A body support structure comprising: a body support member; a base comprising an upper component coupled to said body support member and a lower component adapted to be supported on a floor; an adjustable spring mechanism comprising a biasing spring biasing said body support member, said spring mechanism adjustable between at least a first and second biasing force; and a weighing mechanism coupled to said adjustable spring mechanism, said weighing mechanism moveable between at least a first and second weighing position, wherein said spring mechanism is adjusted between said first and second biasing forces as said weighing mechanism is moved between said first and second positions, wherein said weighing mechanism comprises a height adjustment device disposed between said upper and lower components of said base, said height adjustment device adjustable between at least a first and second height, wherein said height adjustment device comprises: a pneumatic spring comprising a pressure tube coupled to said lower component and a piston rod extending upwardly from and moveable relative to said pressure tube; a housing disposed around the pneumatic spring and coupled to said upper component; an adapter coupled to said piston rod; and a weighing spring disposed between said adapter and said housing, wherein said housing is moveable relative to said adapter between said first and second weighing positions. a body support member; a base comprising an upper component coupled to said body support member and a lower component adapted to be supported on a floor; an adjustable spring mechanism comprising a biasing spring biasing said body support member, said spring mechanism adjustable between at least a first and second biasing force; and a weighing mechanism coupled to said adjustable spring mechanism, said weighing mechanism moveable between at least a first and second weighing position, wherein said spring mechanism is adjusted between said first and second biasing forces as said weighing mechanism is moved between said first and second positions, wherein said weighing mechanism comprises a height adjustment device disposed between said upper and lower components of said base, said height adjustment device adjustable between at least a first and second height, wherein said height adjustment device comprises: a pneumatic spring comprising a pressure tube coupled to said lower component and a piston rod extending upwardly from and moveable relative to said pressure tube; a housing disposed around the pneumatic spring and coupled to said upper component; an adapter coupled to said piston rod; and a weighing spring disposed between said adapter and said housing, wherein said housing is moveable relative to said adapter between said first and second weighing positions. a pneumatic spring comprising a pressure tube coupled to said lower component and a piston rod extending upwardly from and moveable relative to said pressure tube; a housing disposed around the pneumatic spring and coupled to said upper component; an adapter coupled to said piston rod; and a weighing spring disposed between said adapter and said housing, wherein said housing is moveable relative to said adapter between said first and second weighing positions.