What's accurate in estimating calorie burn?

helaurin

I have a Fitbit Versa 2, which can help estimate calorie burn. First thing this morning, I did a 45-minute workout on an elliptical, which also estimates calorie burn.

They are different, and I'd love to figure out which is more accurate/trustworthy.

My Fitbit is connected to MFP, and that put the calorie burn at 200 calories.

The elliptical (Precor EFX 5.17I), estimated my calorie burn at 304 calories.

Both systems have my age, weight, and height. Fitbit & MFP may also use gender in their calculations; I know the Precor doesn't have that as an input element.

Now, I know that in this case, it's "only" a difference of 100 calories, but considering that my base calorie goal for the day is about 1,400 calories for my current height/weight, and that if I want a special treat, I'll need to earn it, then that 100 calorie difference is a significant percentage.

What's more accurate?

briscogun

The Fitbit is actually measuring your heart rate and will generally provide a more accurate figure. Those machines are widely recognized as being wildly off for calorie estimates. They are just generalizations.

cmriverside

Even the FitBit is using an algorithm that is based on general populations.

If your goal is weight loss, why don't you try using the FitBit calories for a month and see? I agree with brisco that 200 is probably closer than 300. In a month you'll have your own numbers to use as a guide. It's the same experiment we all have to run.

If you have a FitBit, might as well trust it until it proves otherwise.

mmapags

Firstly, I'd trust the Fitbit more than the generic estimate on a machine. Machines, including Precor have the reputation for overestimating calories. I'm not familiar with the formula they use at Precor but your Fitbit is set up for you.

That being said, it's all just an estimate to start. Log your Fitbit burn, accurately (with a food scale) log your calories and see where you are after 2 months. Do your real world results reasonable match what you would expect? Or do you need to make an adjustment up or down.

NorthCascades

A power meter, and a metabolic lab.

sijomial

Is your fitbit sending an adjustment for all your exercise and activity up to that point in the day or are you sure that number is purely the exercise record?

Both numbers are possible. Without knowing your fitness level or intensity level no-one can really judge which is more likely to be closer to reality.

Gender isn't really a significant factor - it's how much power you put into the machine.
The precor could measure that but that's no guarantee it converts that to an accurate calorie estimate. At least it would be proportionate though.

Heart rate can be reasonable for some people doing some cardio but the opposite can also be true and it can be miles out (especially for interval training or unfit people or outliers with unusually high or low exercise HR).

If you are using your fitbit for 24hr monitoring then makes sense just to use the one tool and adjust based on long term result.

AnnPT77

Almost certainly, the machine is giving you a gross calorie estimate - one that includes BMR. Many or most do. Your Fitbit adjustment on MFP should only be a net adjustment between what MFP expects you to burn, and what Fitbit says it estimates you actually burned.

I don't know your estimated BMR**, but unless you're quite petite, it's likely to be at least 1200, which would be 50 per hour on average (rough approximation). So, that'd bring it down to a 50 calorie difference. (Unless you're going to start trying to do things like assess whether today's apple is less sweet so has less sugar than yesterday's apple, 50 calories is pretty far down into minor differences. )

On top of that, as others have said, all of those are estimates, so your 4-6 week results (comparing same point in two or more different menstrual cycles for women who aren't yet in menopause) would give you the best answer.

As a working hypothesis, I'd go with the Fitbit adjustment, as more personalized, and more likely to be a net value in context.

** BMR, basal metabolic rate, is what you'd burn if awake but in bed all day, basically.

heybales

Just a tidbit for accuracy of what's happening.

Fitbit did NOT send a workout to MFP with a 200 calorie burn.

What you saw was an MFP adjustment based on Fitbit sending over a Total Daily Burn figure at some point, MFP taking that and estimating rest of the day at your selected activity level, minus what MFP thought you'd burn with no exercise for the day.

That 200 was merely the difference, not the workout. Could have been more than the workout, could have been less.
So bad comparison to the elliptical calorie burn.

You will have to look on the Fitbit app for what it said the workout burned to truly compare.

yirara

Does the fitbit always show net calories? I don't mean the calories that fitbit sends to MFP (mine isn't linked) but the number that is displayed when you click on that workout. I'm almost certain that this one is gross calories, but can't find anything. The reason I think this is because I went on a slow 17km stroll yesterday (lots of geocaching and searching for caches involved), and Fitbit gave me 1400 calories for that. Substracting that from my total calories yesterday would only leave 1300 for the day, which is way below my normal sedentary number. However, adding the bmi over the 5 hours I was out and about to 1300 gives me a number that I'd expect for a total couch potato day.

heybales

yirara wrote: »

Does the fitbit always show net calories? I don't mean the calories that fitbit sends to MFP (mine isn't linked) but the number that is displayed when you click on that workout. I'm almost certain that this one is gross calories, but can't find anything. The reason I think this is because I went on a slow 17km stroll yesterday (lots of geocaching and searching for caches involved), and Fitbit gave me 1400 calories for that. Substracting that from my total calories yesterday would only leave 1300 for the day, which is way below my normal sedentary number. However, adding the bmi over the 5 hours I was out and about to 1300 gives me a number that I'd expect for a total couch potato day.

It shows what was burned during that chunk of time - which is the way the vast majority of info is given for calorie burn. Garmin too.
Databases, machines, most formula's - it's BMR and the extra.
It never shows NET calories.

Calories from watts being the difference in exercise calorie burn.
Which is why when I manually log or correct a bike ride with watts calculated calories - I get the BMR back in there. 85 cal an hour missed can be major after a few hours. And considering I was still spending energy balancing and awake - more than BMR burn was missed by only reading the energy put into the pedals.

Some other math than what you did to see if it looks right - what is BMR level burn for hours of that walk - subtracted from that walk total calories as shown on Fitbit.
Look better?

But yes they belong in there in a replace-only system like Fitbit or Garmin.

I just confirmed on Garmin yesterday actually because I'd forgotten - when you manually add a workout, it assumes you are including BMR in there - the regular total burn for that chunk of time.
So it subtracts out the BMR already in that chuck of time.
So a 987 cal run manually added only increased the daily burn by 893. It removed the 95 cal BMR burn.