Put a Food Token on the first adventurer. For the rest of Combat, it is exactly same as if that adventurer had one more hitpoint (as if the red number were 1 point higher). That means you have to assign one damage more to eliminate him.

If there is an illusionary adventurer surviving from a previous round (created by the Illusion spell), Create Food will apply to him, increasing his hitpoints to 2. (After all, it is magic food.)

The extra hitpoint does not go away at the end of the round. This adventurer can be fully healed by healing abilities or the Regeneration spell.

On the other hand, the Poisoned Meal trap causes one more damage to this adventurer.