Why did the united states use rationing during world war ii?

The United States used rationing during World War II to prevent shortages. Certain goods like food, gas or even other materials like metal for military purposes.

In order to avoid economic shortages or starvation, Americans were given rationing books with removable stamps. When they went to the groceries, a person could only buy rationed goods - like canned goods, oil, sugar or meat - if he or she also presented the corresponding ration stamp.