Survival skills
A human being can survive an average of three to five days without the intake of water. The issues presented by the need for water dictate that unnecessary water loss by perspiration be avoided in survival situations. The need for water increases with exercise.
Starvation
There is insufficient scientific data on exactly how long people can live without food. Although the length of time varies with an individual's percentage of body fat and general health, one medical study estimates that in adults complete starvation leads to death within 8 to 12 weeks. There are isolated cases of individuals living up to 25 weeks without food. Starvation begins when an individual has lost about 30% of their normal body weight. Once the loss reaches 40% death is almost inevitable.