Margin of error in food/exercise

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famoushamish
famoushamish Posts: 14
in Food and Nutrition
What sort of margin of error do you think there is in the daily totals for most people using this site/app? For example:

- the site gives me a number of calories to net based on my height/weight etc (I use the MFP recommendation and don't customize). I am sure there is some margin of error in that depending on variation in individuals, so that is just approximate and not exact.

- I am pretty careful about using my scales and measuring cups for food. But there is probably going to be some errors periodically in that - although hopefully not much. But over time I am sure small errors add up (or maybe they balance out?).

- The calories that get subtracted by most of my exercise are probably fairly accurate (mostly from running), but I am sure there is a decent margin of error in there.


When you take account of all this, what do you think is a good rule of thumb to work on? e.g. if I am within 10% of my daily calorie goal each day, do you think it is likely I am about right? I could probably work it so I hit my calories exactly every day - but I am sure I would be fooling myself if I think I have burned EXACTLY the same number as I have eaten - given all the estimates/possible sources of error.
What do people here work on?

Replies

  • Ninkyou
    Ninkyou Posts: 6,666 Member
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    I think you're waaaaay overcomplicating things.

    The estimation/guidelines MFP sets, as well as any TDEE calculator are all going to be just that, an estimation. I'm not sure there is ANY way to know 100% what the margin of error is.

    However, that being said, If you set MFP (or even TDEE calculators) to a true approximation of your activity level, weigh (in grams) all of your food, and wear a chest strap heart rate monitor, you will get a pretty good approximation of your daily intake & burn.

    But like I said, you can't know 100% the margin. There are too many factors... food labeling, bmr/tdee testing, heart rate, elevation & more will all cause changes in the equation.

    So yeah... keep it simple.
  • Lizzy622
    Lizzy622 Posts: 3,705 Member
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    A big part of this is trial and error. You need to find what works for you. The MFP numbers are a starting point. Personally, I need to eat about 1,000 less a week than calculated by MFP to lose one pound a week and I need to eat a bit more protein and a bit less carbs than the %'s calculated by MFP. I started with the preset and tweaked it until I found what worked for me.
  • Cortelli
    Cortelli Posts: 1,369 Member
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    IMO you're going to have to go by trial and error. Go with what you think is right. Track your weight every day. Look back after a month at the trend line and actual weight lost versus expected weight lost. Readjust as appropriate. The margin of error is going to vary pretty dramatically from person to person, I think.

    I have my goals kind of artificially low and then don't worry too much about hitting them. I also am probably a lot less circumspect about nailing every portion size / calorie intake (I weigh, but certainly not everything) and fussing too much over how much my exercise actually burns. So I figure I am probably over my "goal" but tracking more or less with the actual weight loss rate I am targeting.
  • MoreBean13
    MoreBean13 Posts: 8,701 Member
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    Don't worry about it.

    Ultimately, the way you should work this program is to adjust your calories by your progress- if you aren't losing as much as you think you should be, you tweak the calories a little. Your personal margin of error should stay roughly the same all the time, so it really doesn't matter.

    That said, you should ditch the measuring cups and measure everything by weight on a digital scale- volumetric measurements are pretty inaccurate.
  • cwolfman13
    cwolfman13 Posts: 41,867 Member
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    I did trial and error. MFP gave me a good number to start with...I was as accurate as possible with my intake and usually logged and ate back 70-80% of my exercise calories as per my HRM and made small adjustments from there as necessary per real world results.
  • auddii
    auddii Posts: 15,357 Member
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    Don't forget that if you eat packaged foods, it's acceptable for their calorie count to be off by up to 20%, so there's that too. Try to be as accurate as you can and see if it works. After a month or two, reassess and adjust accordingly.
  • MoreBean13
    MoreBean13 Posts: 8,701 Member
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    Don't forget that if you eat packaged foods, it's acceptable for their calorie count to be off by up to 20%, so there's that too. Try to be as accurate as you can and see if it works. After a month or two, reassess and adjust accordingly.

    you're thinking of restaurant food. The FDA dictates packaged food should be accurate within 5 calories.
  • auddii
    auddii Posts: 15,357 Member
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    Don't forget that if you eat packaged foods, it's acceptable for their calorie count to be off by up to 20%, so there's that too. Try to be as accurate as you can and see if it works. After a month or two, reassess and adjust accordingly.

    you're thinking of restaurant food. The FDA dictates packaged food should be accurate within 5 calories.

    Guess that explains the quest bar lawsuit then...
  • famoushamish
    famoushamish Posts: 14
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    Thanks, going with the tracking weight and adjusting as necessary method. I thought of this question because I have found myself looking at my calorie count and thinking 'oh, I have 100 left, I can eat some more crackers' or something.
    Or looking at my total and thinking 'yay, I ended the day 50 under' and congratulating myself on having a bit of a buffer and being close but under.
    Then today I was thinking that I am probably fooling myself if I think I can really measure my exercise/diet and am overestimating the accuracy of the calculations by MFP if I think 'if i end up with exactly 0 net calories then I am dead on track'.
  • auddii
    auddii Posts: 15,357 Member
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    Don't forget that if you eat packaged foods, it's acceptable for their calorie count to be off by up to 20%, so there's that too. Try to be as accurate as you can and see if it works. After a month or two, reassess and adjust accordingly.

    you're thinking of restaurant food. The FDA dictates packaged food should be accurate within 5 calories.
    And after actually checking the FDA website, it's 20%, and the food doesn't have to be directly tested, it can be estimated from a verified database based on ingredients. Carbs, protein, and other minerals have to have at least 80% of what is claimed. Fat, sugars, and total calories have to be less than 120% claimed.

    ETA: You might be thinking of the rounding rules. Less than 5 calories, they can say 0, less than 50 calories they round to the nearest 5 calories, and over 50 calories they round to the nearest 10 calories.
  • MoreBean13
    MoreBean13 Posts: 8,701 Member
    Options
    Don't forget that if you eat packaged foods, it's acceptable for their calorie count to be off by up to 20%, so there's that too. Try to be as accurate as you can and see if it works. After a month or two, reassess and adjust accordingly.

    you're thinking of restaurant food. The FDA dictates packaged food should be accurate within 5 calories.
    And after actually checking the FDA website, it's 20%, and the food doesn't have to be directly tested, it can be estimated from a verified database based on ingredients. Carbs, protein, and other minerals have to have at least 80% of what is claimed. Fat, sugars, and total calories have to be less than 120% claimed.

    ETA: You might be thinking of the rounding rules. Less than 5 calories, they can say 0, less than 50 calories they round to the nearest 5 calories, and over 50 calories they round to the nearest 10 calories.

    Oh OK my bad. :flowerforyou:

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