IIFYM vs. MFP TDEE: am i missing something?

TheWorstHorse
TheWorstHorse Posts: 185
in Health and Weight Loss
When I first saw the numbers that MFP suggested for me for a 1.5 pound/week weight loss target, they seemed low: 1770 input and 300 exercise calories a day, which I think adds up to a TDEE of 2070, right? But the input number seemed especially odd; BMR for a guy my age is usually about 1800 and, I would guess a TDEE of 2200 to 2400.

So today I went looking for another TDEE calculator. I ended up at IIFYM (after trying a couple of others), did the numbers and came away with a BMR of 1780 and TDEE of 2680. That's substantially different from the MFP numbers.

So here's my questions: is the MFP calculator working for you over the long term? For the well-educated among us, why the apparent big difference between the IIFYM and MFP number? Am I missing something? Is the IIFYM calculator a better option?

Replies

  • neanderthin
    neanderthin Posts: 10,144 Member
    It looks like you didn't use an activity factor and just added 300 for exercise to your BMR. Even sedentary with a BMR of 1700 would bring your calories up to around 2100.
  • rickyll
    rickyll Posts: 188 Member
    Hi, I'm a big believer of trial and error when it comes to finding out your caloric maintenance level.
    These calculators are good ways of starting but they may be off by a couple hundred calories. I suggest take the number MFP gives you and eat that for a few weeks, your body will do the rest. If you go up in weight, no biggie, just reduce your calories and vice-versa, depending on your goal.

    No calculator will ever give you the right amount of calories to eat, only you can determine that. Some people just don't have the patience since it can take up to a month until you're somewhat in tune with how your body reacts to different foods and different amounts of calories (though I've been doing this for over a year and I'm still learning!)

    Sorry I couldn't answer your more technical questions but if you see it my way, the answers to those questions are irrelevant.
  • neanderthin
    neanderthin Posts: 10,144 Member
    Hi, I'm a big believer of trial and error when it comes to finding out your caloric maintenance level.
    These calculators are good ways of starting but they may be off by a couple hundred calories. I suggest take the number MFP gives you and eat that for a few weeks, your body will do the rest. If you go up in weight, no biggie, just reduce your calories and vice-versa, depending on your goal.

    No calculator will ever give you the right amount of calories to eat, only you can determine that. Some people just don't have the patience since it can take up to a month until you're somewhat in tune with how your body reacts to different foods and different amounts of calories (though I've been doing this for over a year and I'm still learning!)

    Sorry I couldn't answer your more technical questions but if you see it my way, the answers to those questions are irrelevant.
    I agree 100%. All deficits should be based on TDEE and from real life trial and error, but like you say, that just takes too much time in this day and age of instant gratification.
  • lamiller82
    lamiller82 Posts: 31 Member
    When I first saw the numbers that MFP suggested for me for a 1.5 pound/week weight loss target, they seemed low: 1770 input and 300 exercise calories a day, which I think adds up to a TDEE of 2070, right? But the input number seemed especially odd; BMR for a guy my age is usually about 1800 and, I would guess a TDEE of 2200 to 2400.

    So today I went looking for another TDEE calculator. I ended up at IIFYM (after trying a couple of others), did the numbers and came away with a BMR of 1780 and TDEE of 2680. That's substantially different from the MFP numbers.

    So here's my questions: is the MFP calculator working for you over the long term? For the well-educated among us, why the apparent big difference between the IIFYM and MFP number? Am I missing something? Is the IIFYM calculator a better option?

    Just doing math in my head, I came up with this. Don't know if it's right, but the math seems to add up.

    Burn 1.5 lb. / week 750 calories deficit per day (3500 calories = 1 lb/week = 500cal/day/lb)
    Exercise calories 300 calories (created deficit)
    This is 1050 deficit built according to MFP's figures.
    Add that to the 1770 they want you to eat and you'd get the TDEE of 2830, which is easily within range of IIFYM, right?
  • lynn_glenmont
    lynn_glenmont Posts: 10,072 Member
    When I first saw the numbers that MFP suggested for me for a 1.5 pound/week weight loss target, they seemed low: 1770 input and 300 exercise calories a day, which I think adds up to a TDEE of 2070, right? But the input number seemed especially odd; BMR for a guy my age is usually about 1800 and, I would guess a TDEE of 2200 to 2400.

    So today I went looking for another TDEE calculator. I ended up at IIFYM (after trying a couple of others), did the numbers and came away with a BMR of 1780 and TDEE of 2680. That's substantially different from the MFP numbers.

    So here's my questions: is the MFP calculator working for you over the long term? For the well-educated among us, why the apparent big difference between the IIFYM and MFP number? Am I missing something? Is the IIFYM calculator a better option?

    Exercise calories have nothing to do with MFP goal calculations; they only come into play in your actual daily logging.

    If you told MFP you wanted to lose 1.5 lbs/week and it gave you a daily goal of 1770 calories, that means MFP is estimating your daily calorie burn before workouts as 2520* (based on height, weight, age, gender, and activity level that you gave to MFP -- and the activity level is not supposed to include workouts in the MFP approach, which calls for you to eat your exercise calories back). So that's about 160 less than the TDEE calculator you used, which is pretty close, especially when you consider that a TDEE calculator is supposed to include your workout calorie burns.

    If that 300 calories a day exercise calories you mention was generated by MFP, it's more or less a recommendation for fitness; it's not included in calorie goal calculations, and if you actually followed the recommendation, the MFP approach expects you to eat those calories back.

    *Edited to add: 1.5 lbs a week requires a 750 calorie a day deficit, and 1770 + 750 = 2520.
  • AlwaysInMotion
    AlwaysInMotion Posts: 409 Member
    The built-in MFP calculations did not work for me. I don't know what formulas they use and I find that frustrating. My original MFP intake estimate was too restrictive - my energy tanked, my performance suffered, and my weight loss stalled. I switched to TDEE-20% (light activity) and - Voila! - I immediately started feeling better and losing weight again. (I use Scooby's Workshop Calorie Calculator. I have not compared Scooby to IIFYM.) On days where I do "above-average" cardio (for me, that's anything over 1-hr at a sustained high intensity), I allow myself to eat back up to 20% of exercise cals over my TDEE limit. For exercise under my 1-hr threshold, I don't "eat back" cals because I figure "light activity" was factored into my TDEE. It seems to be working for me, but those were based off my own "trial and error" findings.
  • TheWorstHorse
    TheWorstHorse Posts: 185
    When I first saw the numbers that MFP suggested for me for a 1.5 pound/week weight loss target, they seemed low: 1770 input and 300 exercise calories a day, which I think adds up to a TDEE of 2070, right? But the input number seemed especially odd; BMR for a guy my age is usually about 1800 and, I would guess a TDEE of 2200 to 2400.

    So today I went looking for another TDEE calculator. I ended up at IIFYM (after trying a couple of others), did the numbers and came away with a BMR of 1780 and TDEE of 2680. That's substantially different from the MFP numbers.

    So here's my questions: is the MFP calculator working for you over the long term? For the well-educated among us, why the apparent big difference between the IIFYM and MFP number? Am I missing something? Is the IIFYM calculator a better option?

    I clearly missing something on the MFP calcluator mechanics. I think that I get it now.

    And, yes, I agree that tracking what you eat and seeing whether you gain or lose over a period of three or four weeks is the best way to figure TDEE and it is actually what I am doing. Guess I was just hoping, a la instant gratification, to know this very instant if I was on track. :)

    Thanks for all the feedback.
  • BusyRaeNOTBusty
    BusyRaeNOTBusty Posts: 7,166 Member
    If you told MFP you wanted to lose 1.5 lbs/week and it gave you a daily goal of 1770 calories, that means MFP is estimating your daily calorie burn before workouts as 2520* (based on height, weight, age, gender, and activity level that you gave to MFP -- and the activity level is not supposed to include workouts in the MFP approach, which calls for you to eat your exercise calories back). So that's about 160 less than the TDEE calculator you used, which is pretty close, especially when you consider that a TDEE calculator is supposed to include your workout calorie burns.

    Yup. MFP's number is your goal to lose the weight you told it you want to lose. It's NOT your TDEE.
  • littlekitty3
    littlekitty3 Posts: 265 Member
    Watch out....another one to blow your minds:

    http://www.health-calc.com/diet/energy-expenditure-advanced
  • twixlepennie
    twixlepennie Posts: 1,074 Member
    I did alternate day IF for weight loss and didn't follow MFP's calorie recommendations (didn't even know about MFP back then). But, I did try MFP's calorie recommendation for maintenance and it was wrong. I had to adjust my calories up by almost 500, in order to get my weight to stabilize for maintenance, and I got that number from Fitness Frog's TDEE calculator. That was spot on and I've been maintaining fine since then :)

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