Why Don’t the Macros on the Nutrition Label Equal Calories?

“Why Doesn’t Fat + Carb + Protein = Calories?” Find out below ⬇️

Okay, so you already know each macronutrient and their calorie totals:

Protein has 4 calories per 1 gram
Carbs have 4 calories per 1 gram
Fat has 9 calories per 1 gram

“Manufacturers have the ability to use one of six different methods when it comes to calculating calories from macros.”

And since the calorie content of food is made up of nothing but the macros stated above, the calorie total (i.e., Calories) at the top of the nutrition label should equal the sum of the Total Fat (9 calories per 1 gram), Total Carbohydrate (4 calories per 1 gram), and Protein (4 calories per 1 gram), right? Well, it’s actually a bit more complicated than that…

This is so because manufacturers have the ability to use one of six different methods when it comes to calculating calories from macros.

1. 4-4-9 Method

The 4-4-9 Method is probably what most of us imagined when we first learned about macros and their assigned calories per gram. I know that was the case with me! It is also the most commonly used method by manufacturers in the U.S. In short, the calories at the top of the nutrition label equal the sum of the macros. So, if there is:

Total Fat 4g                            ➤     (4g * 9cal/g  = 36 calories)
Total Carbohydrate 6g        ➤        (6g * 4cal/g  = 24 calories)
Protein 3g                               ➤        (3g * 4cal/g  = 12 calories)
72 calories

Calories at the top of the nutrition label will equal 72 calories. That’s all there is to it!

2. 4-4-9 Method adjusted for fiber and sugar alcohol carbs

If you’ve ever heard of the term “Net Carbs,” this is what was being referred to. In simplest terms, net carbs are the carbs that your body can digest (think simple and complex carbs. More on this in a future blog post).

Anyway, when you eat a food containing carbs, most of the carbs are chemically broken down into single sugar units in the small intestine. Although, it is important to note that only individual sugar units can be absorbed by the body. So, if the enzymes in your small intestine can’t break the carbs down into individual sugar units (which is the case for fiber and percentage of sugar alcohols), they can’t be absorbed. Fiber passes directly into the colon (The rest of fiber’s journey will be covered in a future blog post). As for sugar alcohols, of which there are many different types (this will be covered in a future blog post), they are only partially absorbed in the small intestine. However, the level/percentage of absorption differs for each type. For example, only 25% of sorbitol is absorbed in the small intestine (while the rest travels to the large intestine, only to be metabolized via gut bacteria). Yet, as for a sugar alcohol such as erythritol, on the other hand, 90% is absorbed before entering the large intestine.

To conclude, the 4-4-9 Method adjusted for fiber and sugar alcohol carbs is basically the same as the 4-4-9 Method, mentioned above (i.e., 9 calories per gram for total fat, 4 calories per gram for protein, 4 calories per gram for total carbohydrate). However, when calculating the calorie total from carbs, this time, it’s:

Total Carbohydrates
- Non-Digestible Carbs & Sugar Alcohols
= Net Carbs

Furthermore, according to the FDA’s Code of Federal Regulations [Title 21, Volume 2], regarding caloric values for carbohydrates, a general factor of 2 calories per gram for soluble non-digestible carbohydrates shall be used. A list of soluble non-digestible carbohydrates can be found here. The general factors for caloric value of sugar alcohols are as follows:

Sugar alcohols and their Calories per gram (g)

3. Atwater

The Atwater method is the method which is most commonly used by the USDA National Nutrient Database for Standard Reference (SR). Unlike previously mentioned methods, when it comes to assigning caloric values per one gram of fat, carbohydrate, and protein, instead of using common conversion factors such as 4-4-9 (i.e., 4 calories per 1 gram of protein, 4 calories per 1 gram of carbohydrate, and 9 calories per 1 gram of fat), more particular conversion factors, based on food type, are used. These are called Atwater factors. For example:

More examples of Atwater factors can be found here.

4. Specific food factors approved by the FDA

An example of a specific food factor approved by the FDA can be seen in the FDA’s Guidance for Industry: Food Labeling Guide. On the topic of Nutrient Declaration, (page 28, N9.) it states the following:

N9. How are calories from alcohol to be calculated?
Answer: Calories from alcohol may be calculated using specific Atwater factors as provided for in 21 CFR 101.9(c)(1)(i)(A). USDA Handbook No. 74 provides a specific food factor of 7.07 calories per gram of alcohol.

To clarify, the FDA approves a specific food factor of 7.07 calories per gram of alcohol.

5. Bomb calorimetry

Bomb calorimetry involves the combustion of the three macronutrients in a type of constant-volume calorimeter called a, yes… you guessed it… bomb calorimeter! Anyway, before we dive into this, let’s take a couple steps back.

To start, there is potential energy contained within all of the foods that we eat. Apples, bubblegum, cottage cheese, you name it! Furthermore, the most common unit of measurement for this potential energy (when it comes to food) is the Calorie, of which there are two kinds:

• small calories (cal): Represent the amount of heat/energy required to raise the temperature of 1 gram (g) of water by 1º Celsius (º C).

• large calories (Cal or kcal): Represent the amount of heat/energy required to raise 1 kilogram (kg) of water by 1º C. It is also known as a kilocalorie. Large Calories are 1,000 times larger than small calories.

Large calories (Cal or kcal) are the calories we’re most likely referring to when it comes to food calories. For example, if Penelope ate a 600 “calorie” dinner, she actually ate 600 Calories or kcals.

So… back to the bomb calorimeter! Why is the burning of the three macronutrients necessary? I’ll tell you why! This is done in order to see how much heat is released, for that heat (as we learned above) is directly convertible to Calories (i.e., one Calorie represents the amount of heat/energy required to raise 1 kilogram (kg) of water by 1 ° C).

So… after burning the three main macronutrients in a bomb calorimeter, on average, the following total Calorie or kcal amounts are released per gram (ISSA):

Bomb calorimeter values

The 4-4-9 numbers that have been referenced repetitively, no … relentlessly … well, 4-4-9-7 now (the added 7 referring to the common conversion factor of 7 calories per 1 gram of alcohol) are actually the physiological energy values (i.e., the value that is actually released from the organism) while the numbers obtained from the bomb calorimeter are the physical energy value. Though most of our macronutrients contain higher amounts of total combustible energy, some of that energy is lost through the digestive process (ISSA).

6. General factors for caloric value of sugar alcohols

The general factors for caloric value of sugar alcohols are as follows:

Sugar alcohols and their Calories per gram (g)

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