Which of the following definitions correctly describes a kilocalorie (kcal) in human nutrition?

A kilocalorie is the amount of energy required to raise the temperature of 1 kilogram of water by 1 degree Celsius and is the unit commonly used to express energy in foods.

A kilocalorie represents the energy content of a gram of carbohydrate specifically and does not apply to fats or proteins, which are measured differently.

A kilocalorie is an obsolete metric used only in historical nutrition studies and has been replaced entirely by joules in dietary guidance for children.

A kilocalorie is a unit of volume used to measure liquid dietary intake and represents 1000 milliliters of fluid consumed by a child.