Math question. I want to calculate each macro as a % of my total calories.

JeromeBarry1
JeromeBarry1 Posts: 10,179 Member
edited January 2019 in Health and Weight Loss
For instance, my total calories today is 2071.

I have 20 net grams carb = 80 calories
I have 153 grams fat = 1377 calories
I have 132 grams protein = 528 calories.

80/2071 + 1377/2071 + 528/2071 = 1985/2071, or about .96.

If all the calories are from carb, fat, and protein, where the heck is that other 4%?

Replies

  • NovusDies
    NovusDies Posts: 8,940 Member
    You always lose some in rounding. If you add up nutrition label macros they will often not match the calories exactly.
  • ahoy_m8
    ahoy_m8 Posts: 3,053 Member
    Good question. Tot Cal’s always > macros added up. I’ve heard others explain it away as rounding errors.

    4% isn’t that bad. It suggests each macro is ~1% under in grams. I’ve messed with calculations where much more was missing, up to 20% (for example in restaurant provided nutrition information). And there’s always missing calories. The error never goes the other way.
  • JeromeBarry1
    JeromeBarry1 Posts: 10,179 Member
    Drat. So if I want more accuracy I'll need some sigma of accuracy in my macro calorie values.
  • JaneQP
    JaneQP Posts: 9 Member
    The values with two significant figures are fat 9.44, carb 3.94 and protein 5.65 calories per gram.
  • ahoy_m8
    ahoy_m8 Posts: 3,053 Member
    edited January 2019
    Exactly. Sometimes you can guess where the error comes in (sketchy info for one thing you had or suspicious ingredients), or you can just straight line the error proportionally across macros. It’s been a while since I cared that much about accuracy. When I did in the past, it was for something I would have again and planned to use the entry repeatedly.
  • JeromeBarry1
    JeromeBarry1 Posts: 10,179 Member
    edited January 2019
    Protein through metabolism is 4.7.
    Fat is 9.44
    Starch is 4.18
    Sucrose is 3.94
    Glucose is 3.72.

    https://www.nap.edu/read/10490/chapter/7#109

    With the different variety of carbohydrates having different values, some dude named Atwater licked his thumb and said "4".
    What he done wrong was round protein down to 4 when he should have rounded it up to 5.

    I guess this means that the mfp food diary is using the 2 sigma values rather than the rounded dumb numbers.
  • NovusDies
    NovusDies Posts: 8,940 Member
    JeromeBarry1 wrote: »
    Drat. So if I want more accuracy I'll need some sigma of accuracy in my macro calorie values.


    It is kind of hard to get more accurate considering most calories are just averages anyway.
  • ahoy_m8
    ahoy_m8 Posts: 3,053 Member
    NovusDies wrote: »
    JeromeBarry1 wrote: »
    Drat. So if I want more accuracy I'll need some sigma of accuracy in my macro calorie values.


    It is kind of hard to get more accurate considering most calories are just averages anyway.

    This is true. Not all zucchini’s are exactly the same, not all animals/meat is exactly the same... it’s all an estimate.
  • Lillymoo01
    Lillymoo01 Posts: 2,865 Member
    There will never be 100% accuracy when nutrition labels are rounded and can be slightly inaccurate to begin with. Add to the fact the even the calories in fresh food will vary depending on the environment it was grown and everything with CICO is a game of averages that hopefully balances out in the long run.
  • NovusDies
    NovusDies Posts: 8,940 Member
    ahoy_m8 wrote: »
    NovusDies wrote: »
    JeromeBarry1 wrote: »
    Drat. So if I want more accuracy I'll need some sigma of accuracy in my macro calorie values.


    It is kind of hard to get more accurate considering most calories are just averages anyway.

    This is true. Not all zucchini’s are exactly the same, not all animals/meat is exactly the same... it’s all an estimate.


    Yep. As a data-oriented person I try not to think about it too much. I have a fairly exhaustive analysis of my weight loss efforts. Comparing my deficit by weight to my deficit by logging really helped me get over my hatred of the scale.
  • rcervetto
    rcervetto Posts: 60 Member
    Since no one else has mentioned this, I'll ask: you reference net carbs above, are you subtracting fiber from your carbs?

    I understand this may be important to you for tracking, but those grams of fiber still have calories, so the 4% may be coming from there. Look at your total carbs for the purpose of % tracking. Could also be inaccurate MFP entries, rounding errors, etc.
  • JeromeBarry1
    JeromeBarry1 Posts: 10,179 Member
    The fiber is not digested in the mouth, stomach, or small intestine. It reaches the large intestine where billions of bacteria live. Some of the bacteria are able to eat the fiber, and these bacteria thrive and multiply. The bacteria live inside me, but are not me. The mass of bacteria in my gut is mostly constant, even as the composition of the individual species of bacteria varies in response to my fiber intake. There is little we do understand about our biome, and much we do not.

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