Food energy

Foods and beverages provide the ‘energy’ in’ part of the energy balance equation. How much energy a person receives depends on the consumption of the foods and beverages and on the amount the person eats and drinks.

There are a variety of techniques used to measure energy, and different units are used to express energy. 

The energy released from carbohydrates, fats, and proteins can be measured in calories – tiny units of energy so small that a single apple provides tens of thousands of them.

Food energy is measured in kilocalories. One calorie is the heat required to raise the temperature of 1 gram of water by 1 degree Celsius and is equal to 4.184 joules.

Usually the equivalent terms Calorie and kilocalories are used. One-half cup of peanut butter with a caloric value of 759 kcal contains the equivalent heat energy to increase the temperature of 759 L of water by 1 degree Celsius.

The most energy rich of the nutrients are fat, which contains 9.4 kcalories in each gram. Carbohydrate foods contain approximately 4.2 kclaories of energy per gram of food. When burned completely in a bomb calorimeter, protein foods yield, on average of 5.7 kcal/g.

The size does not indicate number. An apple can provide about the same number of calories as a teaspoon of salad oil. Apples are mostly water and have few calories for their weight. Salad oil, in contrast is concentrated fat.

Laboratory use bomb calorimeter, to measure total energy value of various food macronutrients. Bomb calorimeters operate on the principle, of direct calorimeter, measuring the heat liberated as the food burns completely.
Food energy