Exercise calories: MFP vs TDEE calculators ?

weedspot

Hi!

I was wondering how TDEE calculators estimate how many calories are burned during exercise. According to most TDEE calculators, in order to lose 1lbs a week I need a 500 calories deficit. Which puts me at ~2000cal a day.

I know that MFP overestimates calories burned during exercise. So how do I know that TDEE calculators don’t do the same ? And that I’m not at deficit to low or to high because I burn more or less than what’s been estimated ?

Lietchi

weedspot wrote: »

Hi!

I know that MFP overestimates calories burned during exercise. So how do I know that TDEE calculators don’t do the same ? And that I’m not at deficit to low or to high because I burn more or less than what’s been estimated ?

You choose a method and then monitor your weight over 6 to 8 weeks, using a weight trend app (Happyscale, Libra). If you're losing at the expected rate, you can continue as before. If you're losing more slowly or more quickly than expected, you can adapt your calorie goal downwards or upwards.

sijomial

You don't know if any TDEE calculator under or over-estimates your calories burned based on the exceedingly vague categories.

But in a few weeks time you will have a better idea of your overall calorie balance judged by your weight trend.

You won't know if your BMR, activity, exercise and food estimates are all reasonably close or if the inaccurcies in one or more areas happen to be cancelled out inaccuracies in others.

The exercise portion of the TDEE calculation is inherently more inaccurate than the MFP method in that you are estimating your duration, intensity and exercise type up front rather than after the event. The advantage is you just have one number to adjust if you need to.

If you think you will like a same every day goal then try the TDEE method, if you prefer a varied daily goal in line with exercise then do the MFP method. TBH the success or failure of either method is down to the person rather than the method selected.

lgfrie

TDEE calculators do not estimate how many calories are burned during exercise.

They estimate two things. First, they estimate your BMR, based on your age, height, weight, gender. They do not (typically) tell you what they think your BMR is, but that is the basis of their TDEE estimate, so it's in there, though not displayed. There are a few different BMR algorithms out there, which is why MFP's suggested calories will be slightly different from, say, TDEEcalculator.net. However, the different BMR calculations are quite close - they could differ by 25 or 50 calories, but not 300. Incidentally, they tend to be pretty accurate, for most people.

The second thing they do is assign a coefficient to multiply against the BMR. No one, except possibly those in a deep coma, burn calories at the BMR rate. It's almost a theoretical construct. BMR must be multiplied by some number to arrive at an estimate of your actual caloric burn rate. This is not an "estimate of your exercise calories". It is, simply, a multiplier.

It is normally assumed that the rock bottom minimum number of calories that a non-comatose person will burn, just getting out of bed, eating, making their way to a TV set to vegetate all day, etc., is 1.2 times their BMR. So, that 1.2 is the coefficient, and that calculation ( BMR * 1.2 ) is typically labeled "sedentary" on MFP and many TDEE sites. Sometimes it is 1.25.

From there, the multiplier becomes more ballpark and "approximate" since, as you move further from the baseline BMR*1.2, caloric burn rate really becomes very specific to the individual. Different TDEE sites use different coefficients to offer different approximate mappings to your daily activity level. For instance, a site could offer 1.2 ("Sedentary"), 1.4, 1.6, 1.8, 2.0, but another one could offer 1.2, 1.5, 1.8, and so on.

They then name these different levels things that humans can sort of identify with, like "Lightly active" or "Work out 2-3 times per week", and so on. But at no point in the process is the program actually saying "lightly active = 300 more calories per day". It's just that if you work out a few times per week, you're probably at a BMR multiplier of around 1.4, so the TDEE calculators do tend to be pretty close. But individual results may vary. Your actual burn rate, as a person who exercises 3x/week, could be 1.3, 1.4, 1.5, 1.6, etc. It depends on many things - how active/inactive you are when you're not working out, how intense your workouts are, etc.

This is why the best approach is to just pick a TDEE category that sounds logical based on your own activity level, monitor your weight, calories, and exercise for 6-7 weeks, and see where things end up. After that amount of time, if you have recorded things carefully, you'll have a very solid idea of your TDEE and won't need an online calculator.

In short, TDEE calculators are guesstimates of your caloric burn rate, and at no point do they estimate your exercise calories. What they estimate is your BMR and then apply a multiplier to it based on rough-sketch categories of typical activity levels.

MFP is a completely different situation than a TDEE calculator. With MFP, the idea is that you get an estimate of how many calories you burn EXCLUDING intentional exercise. This is called NEAT, not TDEE. You're then supposed to determine how many calories you did working out, and eat those (or some of those). For this reason, MFP provides a lot of info on exercise calories, which are invariably too high. If you knock 30 or 40 % off their numbers, you might get to something reasonable. This is very different than TDEE calculators, which are not estimating your exercise calories at all and are just multiplying your BRM by a coefficient like 1.2 or 1.4. But in truth, the numbers total out about the same. MFP might tell you to eat 1800 and then eat your workout calories back, which might be another 300. A TDEE site will just tell you to eat 2100. You don't get more food for doing it one way over the other, sadly.

janejellyroll

You actually DON'T know that MFP overestimates the calories you're burning through exercise. All you know is that it COULD be. It could also be underestimating or it could be just right. The way you tell with MFP -- or any form of calorie burn estimation -- is to track your results over time and then make adjustments as necessary.

sijomial

TDEE estimate is estimated BMR multiplied by a combined activity AND exercise multiplier.
This is a better one than most https://www.sailrabbit.com/bmr/ and you will see the multiplier descriptors are both lifestyle AND exercise.

MyFitnessPal is estimated BMR multiplied by an activity multiplier ONLY multiplier. Exercise added afterwards as a separate item.
Note descriptors mention nothing about purposeful exercise.

There's pros and cons to both approaches but MFP database's exercise accuracy/inaccuracy isn't a great reason to swap to an even more vague exercise estimate from a TDEE site. Depending on what your particular exercises you do might determine simply a better way to get your exercise estimates to at least a reasonable level (which is good enough for purpose).

lgfrie

janejellyroll wrote: »

You actually DON'T know that MFP overestimates the calories you're burning through exercise. All you know is that it COULD be. It could also be underestimating or it could be just right. The way you tell with MFP -- or any form of calorie burn estimation -- is to track your results over time and then make adjustments as necessary.

It's true that any one person can't really know if MFP's exercise estimates are too high, low or just right, but in my experience they are pretty high and I think they are gross, not net, estimates. I have a machine that reports out 450 calories for a workout that its own watts reporting would suggest is ~ 370. So the machine itself is estimating too high (AKA "making up a number that sounds good"), but MFP says it's 585. This has been my experience all along with MFP exercise estimates. When I knock off a third, I get to a number that seems reasonable. But yeah, it's person specific.

janejellyroll

lgfrie wrote: »

janejellyroll wrote: »

You actually DON'T know that MFP overestimates the calories you're burning through exercise. All you know is that it COULD be. It could also be underestimating or it could be just right. The way you tell with MFP -- or any form of calorie burn estimation -- is to track your results over time and then make adjustments as necessary.

It's true that any one person can't really know if MFP's exercise estimates are too high, low or just right, but in my experience they are pretty high and I think they are gross, not net, estimates. I have a machine that reports out 450 calories for a workout that its own watts reporting would suggest is ~ 370. So the machine itself is estimating too high (AKA "making up a number that sounds good"), but MFP says it's 585. This has been my experience all along with MFP exercise estimates. When I knock off a third, I get to a number that seems reasonable. But yeah, it's person specific.

I agree in that I would tend to recommend people start with the default assumption that their calorie burn is being overestimated. If someone was asking for advice, I'd advise that they begin by eating about 50-75% of their exercise calories back and then adjusting after a few weeks of details about their rate of loss. But I wouldn't assume that an online TDEE calculator was any more accurate. At the end of the day, you're just choosing a number and using that to establish your baseline.

spiriteagle99

For me, the MFP numbers actually understate my calorie burn. I consistently eat about 1000 calories a week more than my goal, which has kept my weight stable for several years. MFP's exercise calories are usually about 200 calories less than my Garmin gives me when I look at the day's active calories, but my Garmin gives me a default of 1400 calories for a sedentary senior and on MFP I've been able to adjust the base goal to 1600 to make up the difference.