After one day without food, the body will have used up its carbohydrates, which are stored as glycogen in liver and muscle cells. After that, it's on to the fat reserves. Your average Joe/Jane, weight-wise, has enough fat reserves to live for four to six weeks without food.
Webster Dictionary(5.00 / 1 vote)Rate this definition: 1  Essential(adj) belonging to the essence, or that which makes an object, or class of objects, what it is. 2  Essential(adj) hence, really existing; existent. 3  Essential(adj) important in the highest degree; indispensable to the attainment of an object; indispensably necessary.
vital adjective. âº ânecessary or âextremely âimportant for the âsuccess or âcontinued âexistence of something: The âexistence of a âstrong âopposition is vital to a âhealthy âdemocracy. The âkidneys âplay a vital ârole/âpart in âremoving âwaste from the âblood. [+ that clause] Itâs vital that you ârespond at âonce.