MFP exercise calorie calcs vs. Fitbit exercise calories

afatpersonwholikesfood

I hadn't really compared the two before. I went for a 1.5 mile walk earlier, and it took me 30 minutes. Actually, some of that time was spent waiting for walk signals and returning a Redbox rental, so my time spent in motion may have been closer to 25 minutes. Either way, it was a brisk walk of about 3 mph.

My Charge HR, which logged the walk automatically, showed a 330 calorie burn and 2,800 steps. Using the exercise database on MFP, that same walk shows up as 200 calories. I'm used to people saying that MFP really overestimates calorie burn. My Charge HR uses my heart rate, so I would think that would be more accurate, but it's obviously much higher. I'm not really concerned about this since the average TDEE Fitbit gives me seems to make sense as far as my rate of loss goes, but I am curious how the two compare for other people.

Or am I missing something here? You know, like MFP is showing straight exercise burn because of NEAT, and the Fitbit burn is including my BMR/sedentary burn in the figure for that 30 minute block of time?

NancyN795

That advice mainly applies to manually logged exercise - not exercise that your Fitbit can track well. For comparison, I tried manually logging a 30 minute, 3 MPH walk in MFP and it was going to give me 133 calories. I then went to Fitbit and manually logged a 30 minute, 1.5 mile walk in it and it gave me 91 calories.

In the case of a walk tracked by your Fitbit, it has multiple ways of determining your level of effort - with a Charge HR it can use heart rate plus intensity and frequency of steps.

heybales

The database is not NET, it's gross. As well as treadmills, HRM's, machines, ect.

People will claim huge exaggeration in the database merely because they heard that - few have any idea how it works or why that claim.

For anything that has no specifics to intensity - your effort may not match up well with the effort in the studies that made the entry. No way to know.

But entries that are specific, have a chance of being more accurate than even HRM.

But - and this goes to the FAQ and why it's better to use Fitbit database for manual entries - the studies resulted in calculations using BMR, but MFP converted that to weight based.
But a 200 lb 6 ft 20 yr old male doesn't have the same BMR as 200 lb 5'3" 50 yr old female.
So the farther your BMR is away from what the conversion resulted in, the worse your accuracy.
Both those people would be off using database entry - male would be underestimated, female inflated - for the exact same workout.

The other reason why many think it's way over, is because when you do low level stuff with low calorie burn for a long time, the fact you are only burning say 50 calories over BMR burn anyway starts to add up - but you are given credit for the whole thing - it should be only what is above base burn.

And actually - MFP already has a calculated per min burn figured for you - your daily calorie burn they take the deficit from. BMR x activity factor (like 1.25 for Sedentary).
In reality for proper eat-back method - it should only be what you burn above that figure, which is higher than BMR.
You don't eat back what you were already accounted and expected to burn.

So for people that do a lot of walking - that fact of how it's done starts to add up negatively and you could wipe out a deficit easily when manually logged.
Hence the reason many discover they must take 50% of the stated calorie burn if they want to lose weight.
The database is right (or close because of that weight conversion) - it's the application of the math with their workouts that kills the principle.

What you should do to compare is on Fitbit, using the activity record already there that said how many steps and miles and calories - is leave it and create a manual Workout record of same start time and duration, same distance, but let Fitbit calculate the calories.
Now you can look at both entries and see what's up. In the case of walking, unless you had lots of hills and more weight than your stats say - Fitbit's calculated will be more accurate than HRM estimate.

http://community.myfitnesspal.com/en/discussion/774337/how-to-test-hrm-for-how-accurate-calorie-burn-is/p1

afatpersonwholikesfood

I'm 5'10", female, 30, and 245 lbs. I've been in a caloric deficit and losing weight since the beginning of May 2015.

My Fitbit profile shows my 30 day average burn as 3,336, and it shows my average intake as 1,666.

I got my Fitbit on Nov. 28, and I've lost 34 lbs. since then, so my rate of loss seems to check out with the average daily burn Fitbit is giving me.

I let my Fitbit Charge HR use its SmartTracking (think that is what it is called) to pick up virtually all of my activity. I pretty much do an even mix of brisk walking and aerobics. I don't bother logging resistance work/yoga/pilates/etc.

I made a manual record to see how it would compare. For the same time and distance, it calculated 130 calories - big difference once again. Here's a screenshot of the record for the real walk that Fitbit automatically created for comparison:


I'm probably not going to spend too much brainpower on this, but I do get curious about the data from time to time. The discrepancy is just interesting.

heybales

If I might suggest, when you hit 200 lbs, lighten up that deficit so it's not the current 50% or more - no body is going to like that much deficit.
You'll likely start seeing signs of rebellion before that though, and hopefully not too late to take slight modification to keep it from getting worse.

Must have been some decent hills in that walk for the good variation in HR, or you sped up several times.

afatpersonwholikesfood

heybales wrote: »

If I might suggest, when you hit 200 lbs, lighten up that deficit so it's not the current 50% or more - no body is going to like that much deficit.
You'll likely start seeing signs of rebellion before that though, and hopefully not too late to take slight modification to keep it from getting worse.

Must have been some decent hills in that walk for the good variation in HR, or you sped up several times.

Nope, no hills. Totally flat. Maybe I was varying my speed without realizing it.

I actually eat more now than I did during most of the time I was above 300 - I initially started slowly. My doctor has been supervising my weight loss since I lost the first 20 or so pounds. She takes lab work here and there and checks in with me regularly. One of the things she asks me is if I am suffering or comfortable with the food that I eat, and I am comfortable now. I stuck to 1,200 calories for awhile to get my weight below 300. I wouldn't want to do that for a long time again; my body definitely didn't like that deficit. I increased to my current average (this was before getting the Fitbit and seeing what I burn; I do have days now where I enjoy a 2,000 - 2,200 calorie splurge), and I feel pretty good. 200 is actually my goal weight at the moment (still a bit overweight, but both she and I are happy with that number), so I'll start maintenance when I hit that and not lose any more weight for awhile while I take time to decide whether to stop there for good or not, and I will lose with a small deficit and lots of strength training/protein should I continue from that point. I do have to admit my doctor has pushed me a bit to keep up a fast rate of loss, but maybe that has been a good thing for me (as an individual; I'm not suggesting that everyone ought to lose at this rate).