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.  

[Mite158]

Outside of walking,  my calorie burn on fitbit is also low. In fact I lost a dangerous amount of weight believing it. I started input my own using Log Previous and in some cases adding dummy exercises to get the nutrition I needed without having to look at that shameful OVERBUDGET notice. I wish they would remove that overbudget judgment. The 'share your results' page just gives calories in and calories out. Let's me be the judge of whether I am truly over budget.  

A second tip is how do you feel.  Without and in your own exercises or extra calories,  I noted +/- 200 calories around "In the zone", I was painfully,  painfully hungry.  Once I got 200 under budget,  the hunger almost suddenly went away. Same for way over. So something is not right.

[Rlpow]

100% agreed. My chest strap heart rate monitor calorie burn estimation is WAY different than my fitbit. For example, from 20 minutes of yoga today, my Wahoo monitor said I burned approximately 90 calories, and my fitbit said 23. That is a HUGE discrepancy and while my Wahoo monitor may be overestimating, the fitbit is definitely way underestimating.  The whole reason I got the fitbit was to track my calorie burn during exercise, so super disappointing.

[mjwillis]

Yep, this has been bothering me since I got back into cycling a few months ago. I started a weight loss journey 13 months ago, using diet and a workout program as well as walking (which I have always loved). At first I just relied on TDE estimates, but then was reconciling this with my Fitbit. This seemed fine when these were my activity types and I lost a chunk of weight at the expected rate. More recently I dug the bike out and have now progressed to longer rides. I have noticed the Fitbit calorie readings are way below those of biking/trails apps, which didn't really bother me as they are not personalised.

But yesterday I went for a 60 kilometre ride. The trail passes my gym so I stopped in for an upper body weight session on the outward leg and a core session on the way back. I wore a heart rate monitor the whole time. It calculated my calories at around 2000, whereas the Fitbit gave me more like 1000. 

I have more than reached my weight loss goals (started at 99kg with a goal of 85kg and a 'stretch goal' of 75kg and am now at 67kg) and am more concerned with undereating now than overeating.

I'm wondering whether something like a Garmin would be more accurate, or whether all wrist trackers are going to be much the same. I can't link my current HRM to Fitbit, which is a shame as I would still like to track my TDEE in one place.

[Rlpow]

I ended up returning my Fitbit because I just found it to be too unreliable! Chest strap heart rate monitor works a lot better for me.

[Looby52]

Hi,
I was surprised to get a notification for this post I put up years ago! My
Fitbit died on me at least 2 years ago now maybe longer and would not
charge. I’d not buy another one they’re expensive to have last just a year!
Thanks everyone

[CatBerge]

I have a hard time beleiving that you burn off 2000 calories in a 2.5 hour bike ride with some strength sessions. However, I find that my daily calories in fitbit remains too low, and no one from the company has answered any of our concerns. When I walk 20,000 steps in a day, it estimates my daily calory burn to be 2000 in a day, and I weigh about 57 kg. I would recommend you to not trust fitbit calorie estimates and use another app or function for this.

[Yanz]

Mine is crazy low. I have apparently burnt 900 calories in  total since midnight (its now 3pm) - 300 of which was from 2x 15km indoor bike rides.

It did at one point have me on 900 calories burnt right after my second 15km bike ride finished (at 12:30) but then randomly dropped circa 200 calories from nowhere. And calorie burn went back to resting before heart rate did? 

But even when it doesn't lose calories it seems low. A 30-45 minute hiit workout will only show as burning circa 100-150 calories, and a 75 minute boxfit the max I've ever burnt is 300. I'll admit I am petite (5') so won't burn as much as others but I think that's too low.

Has anyone found a setting or fix for this? 

[Rlpow]

I didn’t find a fix and ended up returning my Fitbit.

[phatbitzr]

Yanz, your description of your workout is arbitrary, so I cannot assess on how your tracker should be performing.

A 15km indoor bike ride means nothing, as if you turn it to resistance level 0, you will have a much higher distance travelled than if it is turned to a much higher resistance, even though the higher resistance workout would have had a much higher heartrate, and much higher calorie burn.

You have to see what your base metabolic rate is, then see how much higher your workout adds on top of that.  You should also correlate that with the heart rate zones you were in during your exercise.  Don't forget, a HIIT workout, you should be hitting close to anaerobic threshold.  If you are gasping for air where you can't speak a word, but your fitbit indicates your heartrate is in fat-burning range, then you are either super athletic or your have an abnormally low peak heartrate.

Fitbit tracks calorie burn based on heartrate, so the lower the heartrate, the lower the calorie burn.

I do have scenarios where the daily calorie burn drops on its own.  That is when I have another device tracking my exercise, and when fitbit sync that exercise over, it doubles up the exercise, but might count the calorie burn at a constant rate, and depending on how hard the exercise really was vs what its new estimated burn rate, the rate could go up or down.

[Julia_G]

Excellent answer @phatbitzr .  Thank you for your contribution!

[Yanz]

Yeah I get all that... bmr is low - circa 1300 so I expect my burn to be lower. I was, however, hitting peak heart rate (high 160s/low 170s) mid resistance, 15km in circa 22 minutes, not quite unable to breathe but pretty much at gasping... 

Last week waked with a friend who, yes, is taller and circa 10kg heavier but also much, much fitter than me and she burnt over twice the calories I did (I was circa 230, she was 560 odd). 

And then there is the random 'roll back' on cals. Watch and app showed me at 900  burned them randomly leapt back to 700 calls for no reason. I didn't 'unburn' them. It just doesn't make sense. 

[phatbitzr]

I am not sure what type of tracker your friend is using, it could only be an apples to apples comparison if she also has a fitbit.  Even then, weight, age, resting heart rate (which would skew one's avg heartrate during the walk) would all skew each one's result.  Look at yours and your friend's cal/min and heartrate for the exercise on fitbit's website.

Maybe the tracker is not picking up your heartrate consistently?  Does your exercise show a high heartrate level throughout the whole exercise?  My usually don't if I move my arm around, or even if it on my wrist while on the handlebar.  I now wear my fitbit with a bungee cord contraption as its wristband and slide it all the way near or above my elbow when on the bike.

When I am on the Keiser bikes, I sometimes look at its calories display and compare it with my fitbit's.  My fitbit's cal count is somewhat higher, but that is to be expected given that the bike doesn't know my BMR, so it doesn't include it as part of the total calories.  I also stop pedaling during recoveries, so the bike stops recording, while the fitbit counts my high heart rate during that time as burning calories.  I mostly look at average watts per session, which is what you should be looking at too (most stationary bikes has that).

As far as riding on a indoor bike, 15km in 22min seems to indicate you are riding at a really high cadence with the equivalent resistance of pedaling with the chain off.  Doing 41km/hr over 22min is unattainable in a real bike ride.  You are not doing productive work any part of your body, thus none gets stronger.  On the Keiser, I probably record 7.5km in 30min of work.

[Looby52]

This post was from years ago!!!! That Fitbit died long ago and I’ve never
been able to afford to replace it!

[Yanz]

Interesting because I also use an outdoor bike and yes, I am slower, but I do 10-11 miles in 45 minutes, but lower leg resistance when pedaling as I live on top of a significant hill so so 50% of my ride is on an uphill in the lowest gears and taken super slow because hills and my asthma don't mix 🤷‍:female_sign:

[Moverton]

I’m having the same issue. Looks like most of us are. 😒