Calories, not what you think!

calories, not what you think!

The Atwater System used to calculate calories is the one we all know.  4 calories per gram of protein, 4 calories per gram of carb, 9 calories per gram of fat, and 7 calories per gram of alcohol.  Trouble is, its just an approximation!  Not only that, a lot of times it is WRONG.  Ever wonder what the whole "net carb" thing was about?  Read on!

kcal != (carbs * 4) + (protein * 4) + (fat * 9)

I cant believe I call myself a scientist. I go thru 54 years of my life looking at nutritional labels every single day and don't notice that the old formula I thought I knew was incorrect.  If you actually USE that formula and plug in the grams of protein, carb, and fat - it rarely adds up to the calories listed on the nutritional label!  At least I was in good company in this misconception, but lets set the record straight.  Here is a great article on the science behind calories listed in nutritional labels:

Bear found that whole almonds have about 20% less calories than the value calculated using Atwater factors. In a separate study, he found that pistachios had 5% less calories than originally thought. This has to do with how nuts — especially whole nuts — are absorbed by the body. With whole nuts, compared to peanut butter or peanut oil, more fat ends up in the poop. People who eat more nuts also lose more fat in the stool.

This whole thing came up because in my new custom meal planner software, the macro percentages were not adding up to 100%. I naturally assumed it was a bug ... but it wasn't!  I tracked it back to the nutritional data being incorrect, that is, when you calculated the calories from the above 4-9-4 Atwater formula, it was off - sometimes WAY off, up to 20% off.   At the bottom of this post is a chart my software generated for the errors found between the 4-9-4 Atwater calculation and the actual calories listed on the nutritional labels.

Here is an article from scientific american on how calorie content is measured, here are the important excerpts:

According to the National Data Lab (NDL), most of the calorie values in the USDA and industry food tables are based on an indirect calorie estimation made using the so-called Atwater system. In this system, calories are not determined directly by burning the foods. Instead, the total caloric value is calculated by adding up the calories provided by the energy-containing nutrients: protein, carbohydrate, fat and alcohol. Because carbohydrates contain some fiber that is not digested and utilized by the body, the fiber component is usually subtracted from the total carbohydrate before calculating the calories.

The key phrase is "... is usually", meaning sometimes yes, sometimes no, sometimes partial. In other words, you cant calculate protein, fat, carbs using the 4-9-4 system accurately.

So what this means to me is that in my calculator, I can only approximate calories because thats all anyone does. Despite the governments best efforts, nutritional labels are just good scientific estimates of the calories. To measure the calories accurately just isn't feasible. Even using an expensive bomb-calorimeter on each of over 10,000 foods wont help because as mentioned above, it depends a lot on what the body does with the fat, carbs, and protein. In the case of the fat in nuts, it seems a lot of it just slides thru the system undigested. Just because you burn the nut and get 130 Kcal worth of energy out, doesn't mean that the body will.

So what is one to do?  The calories listed on the label is just a rough estimate of the calories you are getting and nothing precise. It is what it is!

If you want to lose bodyfat and you are not, its means you need to eat less - it doesn't matter how many calories the nutritional label say you are eating!

Scooby Werkstatt

For those with a scientific curiosity, at the bottom of this page are the differences between the calories listed on the nutritional label and the value calculated by the 4-9-4 Atwater calculations.  Please bear in mind that I have yet to double check all these entries in the nutritional database for accuracy.

As suspected, the biggest difference between the calories calculated by the 4-9-4 Atwater system and the calories listed on the nutritional label are the things with the highest fiber content.  People have wondered where the whole "net carb" thing got started and have wondered if it was just "new math" designed to let people eat more.  No, the "net carb" thing is an attempt to make the math turn out better!

One could look at the above data and come up with a new variant of the 4-9-4 that takes fiber into account that could reduce the error substantially, the question is - why bother?  Even the calories listed on the nutritional label can be up to 20% off so why bother beating ourselves up to perfectly reach that incorrect value?

So back to the problem that started this whole scientific self introspection - how to fix my macro percentages that don't add up to 100% because the nutritional data that everyone uses is wrong?  Well, in the spirit of transparency, here is what I am going to do in my custom meal planner.  To calculate macro percentages, I will use the below formulas

  • protein percentage =( (grams protein * 4) / (calories listed on nutritional label)) *100
  • fat percentage =( (grams fat * 9) / (calories listed on nutritional label)) *100
  • carb percentage = 100 - (fat percentage) - (protein percentage)

The rationale behind this is that it seems that the calories in protein are fairly easy to measure accurately so the nutritional label probably predicts that with a reasonable degree of precision.  Although its a bit difficult to predict the energy that the body will extract from fats, that is probably the next best understood.  The energy the body will extract from the carbs and fiber seems the biggest unknown because we just cant seem to predict accurately how the body can digest nutrients tightly bound with fiber.  Because of that, its probably the most accurate to just assign the carb percent as being what is left over after the protein percent and fat percentage has been calculated.  Its not perfect ... but then neither is having macros add up to 112% :)

 

 

 

 

DESCRIPTION LISTED
CALS
g
pro
g
carb
g
fat
CALC
CAL
ERROR cals Error
%
chicken
breast, boneless, skinless
165 31 0 4 160 -5 -3
beef,
ground, 5 percent fat
171 26 0 7 167 -4 -2.3
turkey,
ground, grilled
235 27 0 13 225 -10 -4.3
egg,
1 whole, jumbo
90 8 0 6 86 -4 -4.4
egg
white, 1 large
16 4 0 0 16 0 0
salmon,
grilled
182 25 0 8 172 -10 -5.5
tilapia,
grilled
128 26 0 3 131 3 2.3
tuna,
canned, white, water pack
128 24 0 3 123 -5 -3.9
greek
yogurt, nonfat
130 23 9 0 128 -2 -1.5
quark,
nonfat
130 23 9 0 128 -2 -1.5
whey
protein powder, unflavored
94 18 2 2 98 4 4.3
protein
powder, vegan
150 21 13 4 172 22 14.7
mixed,
green beans, peas, carrots, corn
50 2 10 0 48 -2 -4
beans,
green frozen
30 1 5 0 24 -6 -20
bell
pepper strips, red, yellow, and green
20 0 4 0 16 -4 -20
spinach,
baby, fresh leaves
20 2 3 0 20 0 0
asparagus
spears, fresh
20 2 5 0 28 8 40
cucumbers
with peels, fresh
15 1 4 0 20 5 33.3
sweet
potato, baked
180 4 41 0 180 0 0
kale,
boiled
28 2 6 0 32 4 14.3
oats 379 13 69 7 391 12 3.2
shredded
wheat, plain
339 11 80 2 382 43 12.7
quinoa 120 4 21 2 118 -2 -1.7
rice,
brown
216 5 45 0 200 -16 -7.4
beans,
pinto
245 15 45 1 249 4 1.6
lentils 230 18 40 1 241 11 4.8
beans,
black
227 15 41 1 233 6 2.6
bread,
100 percent whole wheat, 1 slice
69 4 12 1 73 4 5.8
chia
seeds
490 16 44 31 519 29 5.9
flaxseed,
ground
534 18 29 42 566 32 6
sardines
in tomato sauce
186 21 1 10 178 -8 -4.3
broccoli 98 7 20 1 117 19 19.4
olives,
green pickled
145 1 4 15 155 10 6.9
olives,
canned black
81 1 6 7 91 10 12.3
avocado 160 2 9 15 179 19 11.9
almonds,
dry roasted
597 22 19 53 641 44 7.4
nuts,
dry roasted, mixed, without peanuts
885 22 32 81 945 60 6.8
peanuts,
dry roasted, without salt
814 24 35 70 866 52 6.4
peanut
butter, natural
1517 65 52 130 1638 121 8
almond
butter
1582 38 53 148 1696 114 7.2
olive
oil
1910 0 0 216 1944 34 1.8
egg,
whole, jumbo
90 8 0 6 86 -4 -4.4
chia
seeds
490 16 44 31 519 29 5.9
flaxseed,
ground
534 18 29 42 566 32 6
pinto
beans
245 15 45 1 249 4 1.6
lentils 230 18 40 1 241 11 4.8
beans,
black
227 15 41 1 233 6 2.6
corn,
frozen whole kernel
88 3 21 1 105 17 19.3
salmon,
grilled
182 25 0 8 172 -10 -5.5
soy
milk, nonfat, plain
70 6 10 0 64 -6 -8.6
milk,
nonfat
83 8 12 0 80 -3 -3.6
milk,
whole
146 8 13 8 156 10 6.8
cottage
cheese, nonfat
104 15 10 0 100 -4 -3.8
cauliflower 23 2 4 0 24 1 4.3
brussel
sprouts
36 3 7 0 40 4 11.1
carrots,
baby
35 1 8 0 36 1 2.9
strawberries 49 1 12 0 52 3 6.1
peach,
1 large
68 2 17 0 76 8 11.8
apple,
1 large
116 0 31 0 124 8 6.9
orange,
1 large
69 1 17 0 72 3 4.3
banana,
1 large
121 1 31 0 128 7 5.8
grapes,
red
67 1 17 0 72 5 7.5
blueberries,
fresh
84 1 21 0 88 4 4.8
coconut
oil
862 0 0 100 900 38 4.4
beef,
ground, 30 percent fat
238 23 0 16 236 -2 -0.8
cabbage,
red or green
31 1 7 0 32 1 3.2
tomato 18 1 4 0 20 2 11.1
wheatabix,
plain
339 11 80 2 382 43 12.7
hemp
protein powder
90 15 9 3 123 33 36.7
Cheerios,
plain
100 3 20 3 119 19 19
chia
seeds
490 16 44 31 519 29 5.9
flaxseed,
ground
534 18 29 42 566 32 6
blueberries,
dried
130 1 31 0 128 -2 -1.5

calories, not what you think!