If the bio stat drops down EACH AND EVERY page, then there's a global link script you can use. It will run every time you click a link. Make sure you have scripting turned to advanced, then just do something like this (in the global link script):
%BIO := %BIO - 1
That would make your BIO stat go down by one each time you click a link. If you wanted to send them to a death page once they hit zero, then you'd do something like this:
%BIO := %BIO - 1
IF %BIO <= 0 THEN
$DEST := @P99
Replace "99" with whatever page number you decide you want your death page to be. This way, once they have 0 food, instead of going to the page they were going to go to, they instead go to a page that tells them they starved or otherwise dead. Keep in mind that with this method, if they only have one food and they click a new link, they would starve. If you wanted them to starve after they hit 0 and then clicked a new page, you'd just do this:
IF %BIO <= 0 THEN
$DEST := @P99
%BIO := %BIO - 1
Just do the check before affecting the variable.
That help?