Humans can make do longer without food than sleep. Provided there is water, the average human could survive a month to two months without food depending on their body fat and other factors. Sleep deprived people, however, start experiencing radical personality and psychological changes after only a few sleepless days. The longest recorded time any one has ever gone without sleep is 11 days, at the end of which the experimenter was awake, but stumbled over words, hallucinated and frequently forgot what he was doing.