Calorie Expenditure Charts
For Physical ActivityCalorie Expenditure Charts
For Physical ActivityKatch/Katch/McArdle
The kcal value of any food is measured directly by the amount of heat released when the food is burned in a heat-measuring device called a bomb calorimeter, illustrated in Figure 1. A portion of food is placed within the caloriemeter's small, steel chamber, which is then filled with oxygen. An electric current ignites a fuse inside the chamber and the food explodes and "burns-up" releasing all its energy. A container of water surrounding the calorimeter absorbs the heat released from the burning food. A sensitive thermometer records the increase in water temperature, and provides a precise measure of the amount of heat liberated. For example, when one 4.7 ounce, 4-inch sector of apple pie completely burns in the bomb calorimeter, 350 kcal of energy is released. This is enough heat to raise 3.5 kilograms or 7.7 pounds of ice water to the boiling point. When we speak of the calorie value of the pie, we simply say it contains 350 kcal.
| Figure 1. A bomb calorimeter is used to determine calories in food. A piece of food is placed inside the chamber, which is then charged with oxygen. A fuse and an electric current are used to ignite the food-oxygen mixture. As food burns, the heat liberated is absorbed by a water jacket surrounding the bomb. Because the calorimeter is fully insulated from the outside environment, any increase in water temperature directly reflects the heat liberated during the burning of the specific food nutrient. |
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