Are fitbit charge calories accurate?
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robcarter10
Posts: 5 Member
I previously had a Fitbit Charge without the heart rate sensor. It averaged me from about 2,700 calories on a lazy day to about 3,700 on a day I worked out or was busy. I am 6ft 285 Lbs. This always seemed fairly accurate to me based on what other online TDEE calculators estimated it would be. I also previously owned a Jawbone UP2 and the calorie burn was close to what fitbit says. Well, I just started to use a the Charge HR and the numbers seem really off. For example, yesterday I did 8,466 steps and Fitbit told me I burned 4,431 calories and spent 787 minutes in the fat burn zone, 30 minutes in the cardio zone, and two minutes in peak. All I did was house cleaning and went to walmart. I know that my heart rate it is a little faster than it should be. When I check it while moving around, I am usually between 85-105. However, I doubt that would cause me to burn that many calories.I thought that a heart rate model would be more accurate but feel like it is over estimating by about 500-800 calories. I usually eat somewhere around 3000 calories a day. So, it that number was accurate, I should not have been staying a consistent weight. Has anyone else experienced something like this?
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The first couple weeks of HR-based device usage has the Fitbit trying to decide when your exercise level of HR has started and it should switch from step-based calories to HR-based calorie calculations.
It uses your restingHR as part of that decision, perhaps some other factors, like small numbers of steps still making you go into the fat-burning zone, which should be for exercise only, not daily stuff.
So right now it's probably using HR-based calorie burn for many daily activity things it shouldn't be - exactly for the reason you've observed - inflated calorie burn compared to more accurate step-based calorie burn.
This is exactly why HR-based calorie calc's aren't decently accurate below the exercise zone, nor above the aerobic zone when anaerobic, like strength training.
That should get better once it has a handle on your restingHR after a week or two.
You may also be able to help by setting your own HRmax stat on Fitbit, so that your aerobic zones start higher.
They use the common and frequently wrong 220-age.
Here's some potentially better ones, and you may be higher.
http://www.fitdigits.com/maximum-heart-rate.html
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Thanks for that input, heybales. I just got a Charge 2 a couple weeks ago and have noticed my fitbit calorie adjustment is much higher than with my Fitbit One, even though my steps are lower. I have left the HRM on constantly, so perhaps I should only have it on during exercise. I will also check out the link you posted.0
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I also noticed a huge increase in fitbit's calorie estimate when I upgraded from my flex to my charge HR. The flex was a lot closer as I had it linked and would eat back a portion of the added calories, normally I would have maybe 2500 calories total on a regular day and up to 3000 on active days. However once I switched to the Charge HR I started getting huge calorie increases, sometimes it tells me I burned 5000 calories in a day. This was throwing off my calorie counting so I unlinked my device and only log my exercise based on exercise and minutes now instead of letting fitbit adjust it for me. I was literally getting an additional 1200 calories for sitting around doing nothing.
Being that I had my flex linked for a year and a half I was fairly confident in the calorie estimates as using that plus mfp I was able to drop 70 ish lbs. This is how I knew the charge HR was totally off1 -
KaeChelleA wrote: »Thanks for that input, heybales. I just got a Charge 2 a couple weeks ago and have noticed my fitbit calorie adjustment is much higher than with my Fitbit One, even though my steps are lower. I have left the HRM on constantly, so perhaps I should only have it on during exercise. I will also check out the link you posted.
It may be enabled - but the per second logging and use of HR-based calorie burn would only be when it increases enough along with steps.
Just because it's displaying HR doesn't mean it's using that as basis for calorie burn.
But your idea is indeed the best way to confirm Fitbit isn't guessing wrong as to what is exercise starting.0 -
Out of curiosity, what type of activity is "supposed" to count as fat burning zone (which, I assume, is when the HR-dependent calculations kick in)? Walking, presumably. What about standing and teaching? My FitBit currently says I spend about 4 hours a day in the fat burning zone. Which I suspect means it's counting both walking and teaching time as well as work-out time.0
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From what I've seen if the HR and steps both increase to certain level to like confirm increased activity (not just scared, super hot, upset, ect), a workout will be started and Activity Record created, if it can figure out what the activity is, it may auto-name it too.
I'm starting to think if just the HR goes up, but by enough for long enough, it also decides this is a workout and switches over - not sure if it creates Activity Record though. Perhaps if it can't figure out the activity it doesn't.
By enough means is based on restingHR and HRmax creating the zone levels in the first place.
I think this is also answering the question I had when they changed what restingHR means. It used to NOT be the morning restingHR as is normally meant by that term, but seemed rather to be an average daytime low.
But lately it seemed to go to what restingHR really means, the low of the low at about wakeup.
I was hoping they kept another stat but hidden for that avg daytime low - because that is mighty useful to get an idea of easy walking HR or such.
Resting could be 55 because of being aerobically fit, but because of carrying extra weight, standing and easy moving has HR up at say 90 (which can happen), but then again daytime low at say 70 would show that level isn't really exercise level. But compared to restingHR, it could appear so.
Because simple walking, and definitely not standing, should not be based on HR.0 -
I agree that those shouldn't be HR-dependent and, in fairness, I don't know when the HR calculations kick in. They might only kick in in the cardio zone?0
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From several reports - your's included - I'm getting the sense they start at fat-burning zone. Perhaps part way in to it.
Which for traditional zones that would indeed be fair use of it. HR-based calorie burn can be decent estimate within the aerobic exercise zone (with some known caveats) for steady-state exercise.
Perhaps when you enter the cardio zone is when the auto-Activity Record is created.
But all zone creations I've seen based on HRmax, or including restingHR - don't start at 90 for the first zone, it's always a way up in the range.
For instance, usually given that anaerobic starts at about 85% of HRmax, so from there down to say 50% as bottom of Active-Recovery zone (the original and better name for fat-burning zone), you still wouldn't be reaching the 90 level that avg person starts exercise level at, except for the old 220-age method.
Once at 40 years old (220-40 = 180 calc'd HRmax), then 50% start of lowest zone is 90.
But that would then make 50 yr old start at 85 for exercise level - and that's just not the case because you've gotten older.
I'd hoped Fitbit was using the restingHR to obtain Heart Rate Reserves method, which at least allows accuracy on one side of the range better.
HRmax say 170 - 60 restingHR = 110 HRR x 50% for start of Recovery HR zone.
So 55 result for that + 60 restingHR = 115 start of that zone.
110 HRR x 60% start of Aerobic zone = 66 + 60 resting = 126 Aerobic zone.
If you understand this for your own figures - can you discern what Fitbit is using for the start of your Fat-burning zone?
You'll need Fitbit's restingHR stat, HRmax stat, and that's it. Not sure where buried in the app.
Or if you want to share those stats, I'd love to see what it might work out that they are using for your first zone creation.0 -
I'm 40, so I believe it uses 180 as my maximum heartrate.
My resting heartrate fluctuates between 64 and 66, so call it 65.
As of 2pm this afternoon, I had been in the "fat burning zone" for 122 minutes (just over 2 hours). I had 38 "active minutes".
I can't find a bigger graph for heartrate than the one on the dashboard, but I had absolutely not had a heartrate over 100 for 2 hours. My heartrate crossed the 100 line four times - two just barely touching it (i.e. maybe 2 minutes each?), one for about 5 minutes and one for 10-15 minutes.
I believe the 38 "active minutes" were me walking from my car to my office (almost a mile), walking from my office to my classroom (about 1 km) and back again. The higher heart rates will have been stairs and/or hilly bits. (I work on a university campus. It is not flat.)
Add 75 minutes of teaching to those 38 minutes and you get about 2 hours of "fat burning".
At that point, my FitBit adjustment on MFP was +150 cals over "active". So, that was predicting a total calorie burn of about 2450 cals for the day for ~10,000 steps for a 172 pound 40 year old 5'4 woman. Which might mean that that number was just calculated using steps since 10,000 steps in a day isn't that far off "active".
I was given burns of 2410 and 2426 cals for the last two days, each of which was 11,000-12,000 steps. On working days, I'm closer to 20,000 steps and it tells me I burn almost 3,000 cals/day (or over 3,000 if I worked out as well). That seems slightly high. Based on my intake and weightloss, I estimate that I burn about 2,700 cals/day on average (which would mean slightly higher on weekdays and slightly lower on weekends).
Edited to note that I just walked to the end of the hall and back (a few hundred meters with two flights of stairs in the middle). That added 5 "fat burning" minutes but no "active minutes". My heartrate ticked just over 100 while doing this.0 -
If you understand this for your own figures - can you discern what Fitbit is using for the start of your Fat-burning zone?
I had a heart rate of 90 bpm a few minutes ago and the phone app said that was "Fat Burning Zone". Since I'm 40, that's exactly 50% of my alleged maximum heartrate (calculated using 220-age).0 -
Bummer.
The free research is there to use some much better methods, that's too bad they don't.
I'd consider your situation to probably be in the average of their typical users, that would end up with start of fat-burning zone at 90 (or less if they really keep doing the math that way).
The Active / Very Active levels are based on average METS over a given amount of time, so basically calorie burn level must be high enough, based on HR or step-based, to be given those minutes.
Then again - that test was with body weight squats last spring, so little to no steps, but of course HR went way up for I believe it was 5 min even that the person did it. No A/VA minutes based on high HR.
But maybe that has changed too if HR is giving calorie burn as it is, and that is higher than limit.0
