An hourglass figure

I have an hour-glass figure.
When lying on my bed,
my stomach is flat and narrow,
my curves are where they should be
and I can pretend to be young.

I have an hour-glass figure.
It shows when I stand up,
and gravity comes into play,
it doesn't play fair
and I can't pretend to be young.

I have an hour-glass figure.
It shows as time goes by,
as every moment passes
more of the weight from the top
falls down to my bottom