Starvation and Thirst
Sometimes heroes might find themselves without food and water. In normal climates, heroes need at least 1/2 gallon of fluids and about 1/4 pound of decent food per day to avoid the threat of starvation. In very hot climates, heroes need two or three times as much water to avoid dehydration.
A character can go without water for one day plus a number of hours equal to his or her Constitution score. After this, the character must make a Constitution check each hour (DC 10, +1 for each previous check) or take 1d6 points of damage.
A character can go without food for three days, in growing discomfort. After this, the character must make a Constitution check each day (DC 10, +1 for each previous check) or sustain 1d6 points of damage.