Calculating the percentage of calories in food that come from carbohydrates, protein and fat is easy if the food has a nutritional label. The nutritional label provides the specific amount of carbohydrates, protein and fat in each serving, which you can then convert into percentages of the total calories you consume. This calculation is a common requirement for dieters who need to get a specific percentage of their calories from carbohydrates, protein and fat.
Step 1
Record the amount of total carbohydrates, fat and protein from the food's nutritional label. These values should be in units of grams.
Step 2
Determine the number of calories that come from total carbohydrates. This is given by the equation 4 x C, where C is the amount of carbohydrates in grams. As this equation shows, there are about 4 calories in each gram of carbohydrates. For example, a food that has 12 g of carbohydrates has 48 calories from carbohydrates. (4 x 12 = 48)
Step 3
Assess the number of calories that come from protein. This is given by the equation 4 x P, where P is the amount of protein in grams. As this equation shows, there are about 4 calories in each gram of protein. For example, a food that has 13 g of protein has 52 calories from protein. (4 x 13 = 52)
Step 4
Ascertain the number of calories that come from total fat. This is given by the equation 9 x F where F is the amount of fat in grams. As this equation shows, there are about 9 calories in each gram of fat. For example, a food that has 12 g of fat has 126 calories from fat. (9 x 14 = 126)
Step 5
Calculate the total calories in the food by adding the calories from carbohydrates, protein and fat. A food that has 48 calories from carbohydrates, 52 calories from protein and 126 calories from fat will have a total of 226 calories. (48 + 52 + 126 = 226)
Step 6
Compute the percentage of calories in the food that come from carbohydrates, proteins and fats. This example has 48 calories from carbohydrates and 226 total calories, so 48 / 226 x 100 = 21.2. This means that 21.2 percent of the calories in the food come from carbohydrates. There are 52 calories from protein and 226 total calories, so 52 / 226 x 100 = 23.0. Therefore, 23 percent of the calories in the food come from protein. There are 126 calories from fat and 226 total calories, so 126 / 226 x 100 = 55.8. So 55.8 percent of the calories in the food come from fat.
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