Calories Not Matching Macros – Q&A

Question: This may come across as sounding like a very rookie question so bare with me. I just had a question regarding my macros/calories. My current macros are at 46 fat, 165 carb and 144 protein and calories at 1650. However, recently I have been hitting my macros spot on but not my calories. I am aware that there is 4 calories per gram of carb/protein and 9 calories per gram of fat. What am I doing wrong?

Answer: This is going to be a very short Q&A since I am currently embroiled (perhaps better described as overwhelmed) in the editing of the Women, Training and Fat Loss book.  Just in case anybody is not familiar with the term, macros is simply short for macronutrients and refers to protein, carbohydrates, fats and technically alcohol.  It’s all nutrients that are consumed in large amounts (lots of grams).  Fiber could technically fit here as well.

Calories are a measure of energy.  Technical one calorie is the amount of energy required to heat 1 gram of water by 1 degree Celsius.  This is done in something called a bomb calorimeter and many correctly point out that the human body is not a bomb calorimeter.  But this is all accounted for and yields the Atwater constants.

Nutrient Calories/g
Protein 4 cal/g
Carbohydrate 4 cal/g
Fat 9 cal/g
Alcohol 7 cal/g
Fiber 1.5-2 cal/g

Alcohol is weird in terms of how it affects bodyweight but no matter.  Contrary to commonly held belief, the human body does derive calories from soluble fibers through fermentation in the gut of to Short-Chain Fatty Acids (SCFA).  As well, different foods vary slightly from the above but it’s not major.  So two fats might be 8.8 cal/g or 9.2 cal/g and the above are averages.  But this doesn’t make much difference unless you are looking at extremes of diet.

Technically, diets don’t work in calories (little c) but in kilocalories (1000 calories, kilo = 1000) or Calories (big C).  It’s a math thing, 1000 calories is 1 Kcal but most people use calories and Calories interchangeably even if it’s technically incorrect (a 2000 kcal diet is 2,000,000 little c calories and that’s dumb math).

Now, the above question actually comes up quite a bit, both for individual foods as well as the types of diets.  So you might see on a food label something like this:

Protein: 5 grams (20 calories)
Carbohydrates: 10 grams (40 calories)
Fat: 3 grams (27 calories)
Calories: 90 calories

I’m making up the numbers but the Atwater constants should mean that the food has 87 calories.  And the label lists 90. What’s going on?

Rounding is what’s going on.  Legally, numbers can be rounded up or down depending on the actual amount of the nutrient.  So 5.4 grams of protein becomes 5 on the label.  10.3 grams of carbs becomes 10.  2.7 grams of fat would round up to 3 grams.

Annoyingly, companies can actually round any value less than 0.5 down to zero.  So a food that has 0.4 grams fat is listed as zero.  It’s the same reason they often use absurd serving sizes.  If you take a food that has 0.8 g of fat per serving (which rounds to 1 grams and 9 calories), and cut it in half, you get 0.4 grams of fat per serving which rounds down to 0 and you can list it as zero calories.

But that’s the discrepancy.  The actual calorie count on the foods, if you added them up won’t ever exactly match the macro value of the diet if you math it out.  Due to the rounding.  Since we are not doing clinical nutrition here, this isn’t worth worrying about under most circumstance unless you do something goofy like use a ton of “fat-free” foods (cooking spray is the worst where a short spray may be zero calories but people will spray and spray) and add calories that aren’t being included in the totals.

Told you it would be short.



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