How long can a person live without food and water or air?

A starving person is less sensitive to thirst, so sometimes death is from the effects of dehydration. The weakened immune system also makes an individual more likely to catch a fatal infection. Vitamin deficiency may also lead to death. If a person lasts long enough, the body starts using protein from muscles (including the heart) as an energy source. Usually, the cause of death is cardiac arrest from tissue damage and electrolyte imbalance.