In the nutrition context, “energy” is most commonly used to describe calories. The two terms are used interchangeably, but calories are a defined unit that measures the body’s use of energy.. The body requires energy to function, from breathing to the heart pumping to walking around the home. Different dietary components provide different amounts of calories per gram: Carbohydrates and protein provide approximately 4 calories per gram each, fat provides approximately 9 calories per gram, and other molecules like alcohol (ethanol), nucleotides, organic acids, and sugar alcohols provide very small amounts of calories.

In scientific literature, scientists often use the term “kilocalorie” to be more accurate in describing how much energy is stored in a unit of food. That’s because a true calorie is the measure of how much energy is needed to raise the temperature of one gram of water by one degree Celsius, and. a kilocalorie of energy raises the temperature of one kilogram of water by one degree Celsius. However, on a nutrition label, for example, you may see “calories” used to designate what is more accurately called a kilocalorie.