Health & Fitness
What Is Calorie?
A calorie is a unit of energy; food "calories" are actually kilocalories (kcal), the energy needed to heat 1 kg of water by 1°C.
A calorie is a unit of energy. What food labels call a "calorie" is technically a kilocalorie (kcal) — 1,000 small calories — defined as the energy required to raise the temperature of one kilogram of water by one degree Celsius.
The three macronutrients carry different energy densities: carbohydrates and protein provide about 4 kcal per gram, fat about 9, and alcohol about 7. Daily needs for adults typically range from 1,600 to 3,000 kcal depending on size, sex and activity level.