Calories burned are incorrect - too low for some activities

[porcelina]

HI all,

I am a new member and looking for some help.

I have been tracking and logging fitness and food for many years now via sparkpeople.com. I also used to use a polar hrm for tracking calories burned when I was initially losing weight around 4-5 years ago. Neither of these had the same level of detail as the fitbit, and so I am still getting used to everything and figuring out how it all works. However, I am getting a bit perplexed!

At my goal weight (139 lbs) according to my HRM, I was burning about 400 cals on a 30 minute run and around 600 for an hours high intensity circuits class, sometimes 700 for Body Attack. Spark people would give a lower cal burn because it was more of an estimation than an accurate reading. 

I have been using my fitbit charge hr now for around a week - I have worn it for a 32 minute run, during a 45 minute Body Attack class and then for GRIT strength and CX worx this morning. Each of my burns seems a little low in my opinion: 169 for GRIT, 341 for my run, 356 for Body Attack.

The run probably makes sense to me as it was a gentle run as I am getting over a chest infection, however the gym classes don't. I don't wish to blow my own trumpet or sound conceited but I worked really hard - and always do - in GRIT and Attack. Also, a lot of my friends have fitbits and their burn was a lot higher than mine, and we were all pushing equally as hard together!

I am wondering if I have something set up wrong, or if I am using it incorrectly? The polar unfortunately is broken and it was a couple of years ago when I was using it, so it could be that over the years my body has gotten used to working at high intensity during these activities and so I don't burn as much - however I still feel just as pooped at the end of the sessions as I used to do!! Maybe I need to find some more intense workouts!

Any help would be gratefully received. Thank you.  

[AussieSteveH]

What independent data are you basing this assertion on?

[Julia_G]

Hi, @AussieSteveH, if that question was addressed to me, and you referred to my statement that "if the Fitbit is giving you reasonably accurate heartrate info then it is more likely to be correct than the elliptical", I wasn't basing it on independent data, I was basing it on first principles.  You will note that I prefaced the statement with "if your Fitbit is giving you reasonably accurate HR information" (if not, all bets are off).  For aerobic exercises, heartrate is a pretty good indication of calorie burn.  

Also, of course, I don't know how advanced your elliptical machine is...  at my gym the ellipticals have no means of measuring my heartrate.  Furthermore, they don't require me to input my gender, my age or my height and weight -- and this is all information that the Fitbit has and uses to compute calories.

So if you compare a tool for measuring your calories that has your personal information and is giving you a reasonably accurate heartrate reading it is definitionally going to be more accurate than one that is simply based on what the average person burns for X amount of time at Y resistance.

If you have an elliptical connected to a chest strap, and it knows your gender, age, height and weight, then (and only then) would I bet on its calorie estimation over the Fitbit's. 

I hope this makes it clearer.

[tigger25]

My polar has my data on and it always records more calories burned than the Fitbit. The polar is usually close to the treadmill or bike readings.

[calrenbowie]

Be careful. I thought the calories were low also then I put a chest monitor
on and found out it was accurate. My body was no burning as many calories
that the Internet or other sources say an activity is.

--
Sent from Geeesmail Mobile

[AussieSteveH]

I'm basing my assumption that the elliptical is more accurate on the fact that energy expended can be calculated with physics. That being, the flywheel of the elliptical will have a fixed mass. Moving that mass over a known distance for a known time at a known resistance will take a specific amount of calories to achieve. I trust in science and physics a little more than a gadget that purely measures my heart rate. Nothing more. The caveat here is that walking/running/cycling should be very accurate as gps along with Fitbit data will provide all those variables quite accurately. Also I acknowledge that as exercise equipment ages, it's tolerances and measurement equipment will deteriorate and be less reliable unless calibrated regularly.

[Julia_G]

The physics of the elliptical are known, of course.  But the biology of the person pushing the elliptical, and how many calories he or she is burning, will depend on the amount of energy that person needs to expend to push it -- a calculation without heartrate, gender, age, height, weight, will not make sense.

[Rob19]

I have a Suunto Ambit 2 with a chest strap heart rate monitor and a Charge 2. The profile (height/weight/etc) on both are the same. The heart rate readings from both are very close (I've been using them in parallel).

However, I burn 487 calories in 45 minutes on an elliptical with the Suunto, both only 400 with the Charge 2.

This is clearly not a problem with the heart rate monitor, but with the math behind the calorie burn. It appears that the Charge 2 is under-estimating the calorie burn from elliptical activities. Can someone from Fitbit just explain the math?

[Arachnophobia]

I have the charge 2, I also have an elliptical trainer with pulse monitor, it is also programmed with my age my weight my height etc. As others have said many times over, the calories seem to be way off, on a hard workout they usually come in at 50% on the Fitbit as opposed to the machine, or the app I use (iConsole, which also has all my data programmed in). The machine obviously calculates the tension, speed and, hence energy that you are generating in watts. To get the most out of the elliptical you need to be using the handles and so can't hold on to the pulse reader for the whole workout so Fitbit seemed like a perfect way to keep an eye on my heart rate. However, the calories burned are way off, unless I am sticking to the fat burning zone, in this case the machine and the Fitbit are quite close. This morning I did 30 minutes of hills, with the tension fairly high to begin with, 743 calories burned according to the elliptical, 328 according to Fitbit...

[brigids]

No. It did not. Both devices are wrist monitors, hr measurements almost identical. Why does fitbit consistently record a lower calorie burn than other apps using exactly the same data

[Jussywuss]

Finding the exact same.. I wore my polar (with chest strap) and Fitbit for a HIIT session on an exercise bike.. the Fitbit showed the same HR data as the polar (great!) but Fitbit showed as 65 cals less than the polar.. I got the Fitbit as an "upgrade" to my polar but now it doesn't seem worth it..

[Veryberrystyle]

I have been monitoring my hr a d calories with a navigator good quality watch and when I got the fitbithr I decided to wear them both at the same time. Let's just say that if the fit bit is correct then I night as well never exercise. An hour spin class reads as about 250 working really hard, compared to about 600 on the other watch. I can run 10 kms and it is only a couple hundred calories.  It's so wrong it's a joke

[Mike007]

• Come on Fitbit, please fix this problem. If average HR is the same using different devices, the calories burnt should be the same. I've compared Charge HR to Polar chest strap using Fitdigit. Profile data is exactly the same, average HR is the same, calories burnt with Charge HR are way low. Obviously the formula you use for calculating calories is wrong. 

[Mike007]

This thing is crap! Calories burnt is directly affected by heart rate right? The higher your heart rate is the more calories burnt per minute right? Well please explain these results?

[monchi88]

I am only repeating what has already been said 100x on this thread, but my calorie count is also inaccurate for various exercises, despite the HR average being within very close range. I have a Polar chest strap and have performed the following exercises with both devices on (polar and Charge 2) and received the following average HRs and calorie counts: 

1. Elliptical and weights - 1hr - Polar: 119 hr average/ 422 calories burned; Charge 2: 124 hr average 294 calories burned

2. Barre class - 1 hr: Polar: 114 hr average/ 352 calories burned; Charge 2: 113 hr average/ 201 calories burned

3. Tracy Anderson workout - 51 mins: Polar: 125 hr average/ 365 calories burned; Charge 2: 122 hr average/226 calories burned

You can see that the HR averages for all three different workouts are pretty close, which is great, yet the calorie count on the Charge 2 is under by at least 100 calories! This clearly just means that fitbits way of calculating the calories burned is inaccurate, right? How difficult is it to fix an algorithm to put an end to this issue? The "type" of exercise I input to each device is the same, my age, height, weight, and sex are all the same... what gives? What a disappointment. 

[Mike007]

Hey Monchi, as you can see from my previous posts I agreed with you a few days ago, but after a lot of research I now believe Fitbit is actually the more accurate one and my other apps using the polar hrm have been over calculating all this time. 

[Julia_G]

Most people, and aparently many systems, vastly over calculate calories burned from exercise.  I think Fitbit is correct.  Unless you are following Fitbit's systems and actually losing weight, I would go with them.

[Mike007]

I think u mean NOT losing weight Julia lol

[monchi88]

Hey Mike, thanks for the insight. What kind of research did you find that makes you think Fitbit is actually correct? I'm not disagreeing with you but the low cal counts just don't "feel right", but perhaps that is because I've always used the polar strap and got accustomed to the high calorie counts? 

[Mike007]

Hi monchi,

For the last couple years I had a Flex to count my daily steps but always used a polar HRM linked to Digifit, now called Fitdigits, when I worked out. If I ever did a walk with only my Flex the calories were always way lower, which I put down to being wrong because my hr wasn't being recorded. I had in my head that it didn't matter what exercise I was doing, the higher my hr the more calories I burned, which I now know is wrong. For example, it's much easier to get your hr higher riding a bike as it is walking/running.

I recently got a Charge 2 because I was sick of wearing the strap and wanted an all day read of my hr, and was immediately disappointed with the calories burned. I started doing multiple tests to compare, and lots of reading online. To make a really long story not quite as long, I'll tell you the two main points that finally made me believe Fitbit was accurate.

Polar HRM and Digifit would always log a way higher calorie burn per min riding than walking with about the same actual effort, which obviously can't be right. My Charge 2 logs walks and rides at the same CPM burned even though my average HR is a fair bit higher riding. Same effort = same calorie burn right?

And the second thing was I decided to forget about all the gadgets, heart rate, age, height etc etc and just google "calories burned walking". I read multiple results and not one of them came anywhere near the calories I was apparently burning with the Polar HRM with Digifit. Every one was actually under what Fitbit was recording, which I put down to the lack of the other info not taken into account.

Sorry this was so long winded but I hope it made sense. In the end, ultimately it's up to the individual what they want to believe.

Cheers Mike

[Julia_G]

Hi, @Mike007, no, I did mean losing weight.  If the Fitbit is UNDER counting calories, and you are actually burning much more calories than the Fitbit thinks, you might find yourself losing weight... (assuming, of course, you eat based on the information Fitbit gives you).

If you don't find yourself losing weight by using the lower calorie burn calculations, that would suggest the lower burn is correct.