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)
Its not accurate … but its better than have 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 |