A calorie is a unit of energy used almost exclusively to measure the net energy in food. The calorie content in food is an essential piece of information for a sensible diet. Food manufacturers frequently provide the number of calories in a serving of food, but you can also calculate it directly from the amount of protein, fat and carbohydrates in the food. This calculation provides only an approximation of the net energy in food, since the digestive efficiency of individuals can vary dramatically.
Step 1
Obtain the number of grams of protein, carbohydrates and fat in a serving of the food. The U.S. government generally requires this information on the food's nutritional label.
This example assumes the serving of food has 6g of protein, 3g of carbohydrates and 2g of fat.
Step 2
Compute the number of calories from protein in the food by multiplying the number of grams of protein by 4.
The food in this example has 6g of protein, so the food has 6 x 4 = 24 calories from protein.
Step 3
Calculate the number of calories from carbohydrate in the food by multiplying the number of grams of carbohydrates by 4.
The food in this example has 3g of carbohydrates, so it has 3 x 4 = 12 calories from carbohydrates.
Step 4
Derive the number of calories from fat in the food by multiplying the number of grams of fat by 9.
The food in this example has 2g of fat, so it has 2 x 9 = 18 calories from fat.
Step 5
Add the number of calories from protein, carbohydrates and fats together to get the total calorie count in a serving of the food.
The food in this example provides 24 calories from protein, 12 calories from carbohydrates and 18 calories from fat. The total calorie count of the food is therefore 24 + 12 + 18 = 54 calories.
Things You'll Need
- Nutritional label
- Calculator
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