How Is a Calorie Measured in Food?
What is a Calorie?
A calorie denotes a unit of energy. In food people often use calories as a way to measure energy in food. A calorie in science is what it takes to raise the temperature of water by one degree Celsius. Of course, when we think of calories we think of how much energy there is in a food, or how many calories will cause us to gain or lose one pound of body fat. In fact, calories for food are not even calories at all, but are actually kilocalories.
Breaking it Down
Calories are measured by breaking the food down into its essential parts, namely fats, proteins and carbohydrates by grams. A gram of fat has 9 calories, a gram of protein has 4 calories and a gram of carbohydrates also has 4 calories.
To obtain the amount of calories in a product, the United States Department of Agriculture (USDA) requires a piece of equipment called a calorimeter. The food to be tested is placed in the calorimeter and burnt. The calorimeter is able to measure the amount of heat released from the food. The energy density from the calorimeter can then be converted to calories. However, since some calories are lost during digestion, the final number is then multiplied by 89 percent to make up for that calorie loss.