How is a calorie defined?

• A. A rate of metabolism
• B. A unit of weight
• C. A measure of vitamin content
• D. The amount of energy stored in the food we consume

Answer: (D)

A calorie is a unit of energy used to quantify the energy available in food. In nutrition we usually refer to kilocalories, the amount of heat needed to raise the temperature of 1 kilogram of water by 1 degree Celsius (one kilocalorie equals 1,000 small calories). On food labels, “calories” almost always mean kilocalories. The energy in foods comes from macronutrients: fat provides about 9 kcal per gram, while carbohydrates and protein provide about 4 kcal per gram, with alcohol around 7 kcal per gram. This stored energy is what the body uses to fuel basal functions, physical activity, and other processes. The option describing the energy stored in the food we consume best captures what a calorie measures.