Starvation is a state of extreme hunger resulting from lack of food over a long period of time.
From a medical standpoint, most agree that human beings can survive for up to eight to twelve weeks without food as long as they have water and some salt, although some people in history have fasted much longer. ... Reports have revealed that a person with extra body fat can last up to 25 weeks or more without eating food. This is achieved when the metabolism in an obese individual’s body supplies it with energy as it uses the generous supply of fat storage. 
Starvation as a weapon
"At its peak the Warsaw ghetto had 500,000 people — about 40 percent of the population of Warsaw — crowded into a space comprising less than 5 percent of the area of the city. A meeting was held in Germany by top Gestapo officials, including Adolf Eichmann. This meeting was attended by some of the leading Nazi physicians. They had calculated that if the inhabitants of the ghetto received no more than 800 calories of low-protein food per day, the entire population would be dead in nine months — a simple solution for the destruction of the Jews in Nazi-occupied Poland. Thus hunger and starvation were universal throughout the ghetto.
However, the Nazis had not counted on the ingenuity of the inhabitants. Smuggling was rampant by organized groups, often containing children. Although many things were smuggled in, including arms, the most important was food. Finally, the Nazis gave up the idea of starving the population to death [deciding it] would take too long. Instead they instituted the Final Solution and deported most of the population to the death camps. At the end an uprising broke out and, to the surprise of the world, lasted many weeks. In the end the Nazis destroyed the ghetto, leveling the buildings to the ground and killing the few survivors."
Notes & references
- Health A to Z: Starvation
- Scientific American:How long can a person survive without food?
- Winick, Myron (Williams Professor Emeritus of Nutrition) 2005 Hunger Disease: Studies by the Jewish Physicians in the Warsaw Ghetto, Their Historical Importance and Their Relevance Today. Columbia University in the City of New York. Accessed April 2008.