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Why does burning a food item provide information about its value as a food? The nutritional value of food can be measured on many different scales. The most basic measurement scale is the free energy content of the food. In other words, how much energy is released when chemical bonds within the food are broken? The energy content of food is measured in calories, the amount of kinetic energy required to raise the temperature of one ml of water, one degree. Food is burned under controlled conditions, breaking chemical bonds and releasing free energy. The burning is chemically similar to the breakdown of food in cellular respiration although the process occurs much more quickly and in a less controlled fashion during ignition. Calorimeter can measure the energy in food, but can not measure the digested energy of what we have.

Burning food items helps assess their nutritional value by measuring the free energy content, indicated in calories. This process, although faster and less controlled than cellular respiration, breaks chemical bonds to release energy. While calorimeters can quantify this energy, they do not account for the energy actually digested by humans.