Energy (nutrition)
Energy in nutrition is the chemical energy food supplies for bodily functions and activity, commonly expressed in kilocalories or kilojoules.
Calorie: A unit of energy; in food labeling, one Calorie equals one kilocalorie, or 4.184 kilojoules. Food energy labels report Calories, linking the amount eaten to a standard energy unit.
Macronutrient: A nutrient required in relatively large amounts, especially carbohydrate, fat, or protein. These major nutrient classes account for nearly all energy counted in ordinary foods.
Food label: A standardized panel on packaged food listing nutrition information such as energy and nutrient content. Its energy declaration translates food composition into a number consumers can compare.
Energy balance: The relationship between energy intake and energy expenditure over a period of time. It describes the comparison between food energy and bodily use, not the energy content of food itself.
Bomb calorimetry: A method that measures a sample’s heat of combustion in a sealed, oxygen-filled vessel. It measures food’s gross energy before accounting for energy unavailable to the body.
Carbohydrate: A class of sugars, starches, and related compounds that can supply energy to the body. Carbohydrates provide about four kilocalories per gram under standard food-energy estimates.
Dietary reference intake: A set of nutrient-intake standards used to assess and plan diets for populations and individuals. Energy requirements are estimated within this framework, with age, sex, and activity considered.
Energy expenditure: The energy the body uses over time for maintenance, movement, and other processes. Food supplies energy; expenditure describes its use and helps determine changes in body stores.
Atwater system: A method for estimating food energy from its protein, fat, and carbohydrate content using conversion factors. Its factors underpin the energy values commonly printed on nutrition labels.
Dietary fat: Fat consumed in food, consisting chiefly of triglycerides and supplying concentrated dietary energy. Fat supplies about nine kilocalories per gram, more than other major energy-yielding nutrients.