The stats seem shaky overall, at one time I even had -15 value in some stats (haven't been able to replicate). Stats seem to change as hunger and thirst change, but not by 1 point debuff on reaching 80 hunger/thirst like it was explained in the prologue, rather it happens before that threshold and by a lot more points. Since I'm unable to drink, as previously mentioned, I can't really test if the buffs are working as intended