Food is any material consumed in order to supply nutrition to the organisms. The basic function of food is to store energy (calories) in the form of glucose, so that the organisms can use it during energy production. More precisely, food is any material that is consumed but not immediately metabolized by the body to give rise to a direct nutrient input to the cells. In simple terms, food is the stuff that your mother ate for lunch – the same stuff that you ate for dinner last night.
The human body requires a diverse array of substances in order to survive, among which are food, fat, water, and mineral substances. The food pyramid is a diagram of how much of each nutrient a human needs, as compared with the average amount that is ingested by an adult. It illustrates the point that what you eat is the major determinant of your health, because the nutrient value of any food is directly related to its calorie content.
Generally speaking, food can be categorized into three basic groups: carbohydrates, protein and fat. Carbohydrates are the primary source of energy in the human body, including all living things that contain sugar, as well as in plants, in fact. Protein is the building block of all living tissue, including skin, muscles and organs. Fat is the storage of this fat, which can also be used as energy or simply used as storage.