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.
necessity. 1  something necessary or indispensable: food, shelter, and other necessities of life. 2  the fact of being necessary or indispensable; indispensability: the necessity of adequate housing. 3  an imperative requirement or need for something: the necessity for a quick decision.