Calculating Percent kcal from Macronutrients What is a percentage? In mathematics, a percentage is a number or ratio that represents a fraction of 100 or 1

Subject:BiologyPrice:4.87 Bought7

Share With

Calculating Percent kcal from Macronutrients

What is a percentage?

In mathematics, a percentage is a number or ratio that represents a fraction of 100 or 1.  Percentages are often expressed by utilizing the symbol % or sometimes expressed as a decimal. For example, 35% is equal to the 0.35 expression.  When the % symbol is utilized, it is representing a fraction from 100; however, when the decimal version is used, it represents a fraction of 1. It is important to remember that when dealing with percentages, it will always be part of a whole and never bigger than the whole. For example, you can never have a % that is greater than 100. Why is that? If you only had one pie, this pie will represent our 100% or a whole.   How could it be possible to eat 110% of that pie, when there is only one whole pie?

Now let's move on to calculating the percent of kcal that comes from each macronutrient. To calculate the percentage of energy derived from each nutrient requires the following equation:

kcal from individual macronutrient   x 100 = % of energy from that macronutrient

                                      Total kcal

In order to use that equation, we have to first calculate the kcal from each macronutrient. To determine this, you must first remember that every gram of carbohydrate yields 4 kcal of energy (4 kcal/g), every gram of protein yields 4 kcal of energy (4 kcal/g), and every gram of lipid yields 9 kcal of energy (9 kcal/g). While alcohol is not considered a nutrient, it does yield energy. Every gram of alcohol yields 7 kcal of energy (7 kcal/g). To perform your calculations, you begin with the number of grams for each macronutrient (and alcohol if present).  For example, if we looked at the nutrition facts panel on a 12 ounce can of regular beer, we would find the following information:

Carbs = 13.2 g      Lipids = 0.0 g      Proteins = 1.2 g      Alcohol = 12 g

With these values, you can then calculate the total kcal value for each as shown below.

13.2 g of Carbs x 4 kcal/g = 52.8 kcal of energy from carbs in this can of beer

0.0 g of Lipids x 9 kcal/g = 0 kcal of energy from lipids

1.2 g of Proteins x 4 kcal/g = 4.8 kcal of energy from proteins

12 g of Alcohol x 7 kcal/g = 84 kcal of energy from alcohol

Next, add all kcal values from each macronutrient and alcohol together to determine the total kcal.

52.8 kcal from Carbs + 0 kcal from Lipids + 4.8 kcal from Proteins + 84 kcal from Alcohol = 141.6 Total kcal of energy in this can of beer

Now that we know how to convert grams into kcal and calculate total kcal, we can now move on to calculating percent of kcal from macronutrients. Continuing with our beer example from above, we are going to use the following equation:

kcal from individual macronutrient   x 100 = % of energy from that macronutrient

                                      Total kcal

 

Let's begin with carbohydrates. We determined earlier that there are 52.8 kcal from carbohydrates and 141.6 total kcal in that 12 oz. can of beer. Plugging these values into the above equation, we get:

52.8 kcal from carbohydrates x 100 = 37.28 % of kcal came from carbohydrates in that beer

141.6 Total kcal                  

                                

(Note: 52.8 kcal ÷ 141.6 kcal = 0.372881356 - you must round to the nearest 10,000^th to get 0.3728. Remember that once you multiply this value by 100, you can add the "%" sign.)

Now we need to repeat the same process for lipids, proteins and alcohol. See below.

___0 kcal from lipids____   x 100 = 0 % of kcal came from lipids

                       141.6 Total kcal

               

_4.8 kcal from proteins_ x 100 = 3.38 % of kcal came from proteins

                       141.6 Total kcal

 

_84 kcal from alcohol____  x 100 = 59.32 % of kcal came from alcohol

                       141.6 Total kcal

Once you have calculated your percent kcal from your macronutrients (including alcohol if present), you always want to double check your math to see if your calculations are correct. Remember that percentages are part of a whole.  If you add up all of your percentages, it should equal 100%. Continuing with our beer example:

37.28 % of kcal from carbohydrates

+                    0 % of kcal from lipids

+                3.38 % of kcal from proteins

+              59.32 % of kcal from alcohol

99.98 %

 As you can see this does not add up to be exactly 100 %. This is because we rounded to the nearest 10,000^th of a decimal for the carbohydrate, lipid and alcohol calculations. As long as you are within 0.1 %, then your math checks out.

Now it is your turn to practice.

Examine the table below that shows data for a breakfast and answer the following questions.

Food

Serving Size

Servings Consumed

Carbs(g)

Protein(g)

Lipids(g)

Fiber(g)

Calories

Alcohol(g)

Time

Quaker Oats

69g

1

49g

11g

10g

6g

310

0g

07:30

Grape Juice

8oz

1

33g

1g

0g

0g

140

0g

07:30

               1. What is the total kcal for this meal? Show work to get full credit.

               2. What is the percent of kcals from carbohydrates? Show work to get full credit.

               3. What is the percent of kcals from proteins? Show work to get full credit.

4. What is the percent of kcals from lipids? Show work to get full credit.

5. What is the percent of kcals from alcohol? Show work to get full credit.