How accurate are the calories burned?

[JennyRebecca]

I'm using my Charge 2 with the calories counting app My Net Diary.  They are linked together.  So far I'm averaging almost 2 pounds per week.  I couldn't be happier about that.  It's going really well and I feel amazing!

At the end of the week, My Net Diary tells me based on what I've eaten and what I've burned, what I should have lost that week.  It's always a lot higher that what I actually loose.  I should add, I'm honest about the food I log.  I only answering to myself so why lie to myself.  lol

So does that mean I'm buring less calories than my Fitbit says?

[A_Lurker · Accepted solution]

@JennyRebecca- the HR trackers can be a bit high (the non HR ones a bit low).  A lot will depend on how long you've been tracking as weight loss isn't always linear.  Also, I wonder sometimes about fitness level.  When I first started tracking weight loss vs. deficit I thought the difference was higher (15%+) however, the longer I tracked the closer it came to 10% off.  I figured it was more to do with collecting more data.  I was talking about fitness level yesterday and I remembered that even a medium paced walk to our warehouse and back would push my heart rate into the peak zone.  Now I'm at the point where I'd probably couldn't do that even if I tried to increase the pace.  So it's possible as my fitness level has become better that the tracker is more accurate.

Like everything though, BMR (which is what your average calories burned are if you do nothing) is an average number.  Some people will burn more, some people will burn less.  If you have data/results from more than 3 or 4 weeks you can use that and adjust.  The only suggestion is that you work out your BMR and don't eat consistently below it.  I know everyone is in a hurry to lose all their weight, but it rarely came on quickly, so it's not realistic to expect it to come off any faster.  You can put your information into the following site:

http://www.fat2fittools.com/tools/bmr/

[JennyRebecca]

Thanks @A_Lurker !  That's great information.  I have my calories set for a 1.5 lb loss per week which is 1510 calories a day.  During the week I always hit that and some days may go just a tad over.  Saturday a typical go a few hundred over that since it's our church day and we have a really yummy meal for lunch. 

The amazing thing is I'm still eating all the things I love (well minus drinking sweet tea) and eating what my family is eating and I'm losing weight.  I'm just changing my portions.  It's so freeing and doesn't feel restrictive at all.  🙂

[A_Lurker]

@JennyRebecca- that makes for good, sustainable weight loss.  Best of luck!

[Bigjohn1]

I use FitBit and wonder how accurate is the burned calorie tracker.  Does anyone have any idea?

[Dominique]

@Bigjohn1: there is no universal rule that all Fitbit trackers estimate calories burned for everyone with +/- 2% accuracy. We’re all slightly different, yet Fitbit has to assess our metabolism using a standard equation that relies on age, gender, height and weight. And metabolism is just one variable: the algorithm in your Fitbit must convert moves detected by it, heart rate (if supported) etc. into energy expended. It’s not exact science!

If you really want to know, log all your intake (everything you eat and drink) and measure your weight. Do this for 3-4 weeks. Based on the weight change and calories burned reported by your Fitbit, you will know whether it underestimates or overestimates your energy expenditure, and by how much. 

[noah_holt]

I feel the same way. My wife can't get over the idea that she doesn't have to deny herself(outside of her soda addiction) in order to lose weight. However, I am sitting here as living proof. I eat what I want every day. I just count calories and plan accordingly. And it is working. I am averaging about two pounds per week.

[Daves_Not_Here]

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@Bigjohn1 wrote:

I use FitBit and wonder how accurate is the burned calorie tracker.  Does anyone have any idea?

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Hi @Bigjohn1 - I believe the accuracy varies by person.  In my case, Fitbit underestimates my calorie burn by about 180 calories per day.  Besserwisser @Dominique described how to determine the inaccuracy:  measure your results over time and determine how many calories Fitbit would have add or subtract each day for your predicted weight to match your actual weight.  

[bspiglejr]

Short answer is the tracker is not accurate.  A study done indicates that the fitbit tracker will be off anywhere from 20 to 60 percent in either direction depending on activity.  Walking and running tend to overestimate the calories burned while biking and household activities (sweeping, gardening, etc.) tend to be underestimated.  Here's an article for more info :https://www.washingtonpost.com/lifestyle/wellness/fitbit-and-jawbone-are-accurately-tracking-steps-b...

[Daves_Not_Here]

@bspiglejr - thanks for posting the link - very interesting.

But, you have to admit, it's pretty funny that the Washington Post could bring itself to publish an article about the accuracy of anything.  Maybe Harvey Weinstein should write a book on dating advice?

[Gelcap]

Low blow! I'm biased because I used to work there, but the WaPo has a better track record of accuracy than pretty much any other paper in the U.S.. Possible you're confusing it with The Washington Times? The latter doesn't do much actual reporting but they're known for deeply misleading editorials.

[Daves_Not_Here]

@Gelcap -- yeah, the Washington Times is pretty funny, too.  I'm surprised more is not made of their association with the Moonies.  More and more these days, I'll see references to articles in the Washington Times that treat it like a mainstream paper and don't mention the church.

About the only paper I can read with a straight face is the Christian Science Monitor.

[noah_holt]

I have a suggestion. How about leaving this forum to its intended purpose, which is fitness. The internet has turned into a very ugly and unwelcoming place. And I am sure you guys can move in any direction to spout your divisive drivel. Let us all have this place without destroying it.

Sent from my iPhone

[Daves_Not_Here]

@BruceBu - oh, you're right!  You got me there.  I guess I'm the one who got petard hoisted!

[Gelcap]

That sounds right. Though from "divisive drivel" I'm guessing you're more
Team Problem than Team Solution.

[BruceBu]

Calories burned are not very accurate for most fitness trackers. Average errors are 25-50% simply because of the wide variability in individual metabolic efficiency, with Fitbit's accuracy somewhere near the middle of the pack (Samsung by far worst). If you want accurate calorie burn you need to use one of those breathing masks & instrumentation that measure actual oxygen consumption. A scientific comparison of the heart rate and energy expenditure accuracy of various trackers can be found here.

[Anodyne2k]

Just to add extra voicing to this: your FitBit will never be totally accurate for calorie burn. There’s too many variables to consider. HR trackers really help narrow the margin of error but I’ve read that the BEST non-clinical metabolic trackers were anywhere from 7-9% inaccurate. I used the BodyBugg shortly after the Biggest Loser really started pushing it and it was very close to calories burned and I was extremely close with logging food and calculating weight loss. The scale affirmed it. That tracker was an arm band, not a wrist wearable and was bought out by Jawbone and discontinued (sadly).

For the FitBit I wanted to get accountable to activity and lose weight I’ve slowly put back on over the years and knowing the FitBit trackers (I use the Charge 2) are inaccurate I started with a 10% reduction in calories burned. So if my tracker says I burned 4500 calories, I subtract 450 and that’s was my working baseline. But that’s a 10% error margin and I’ve heard FitBit can be 12-15% off, so I adjusted you 12% variance which makes a little more sense. I don’t use the scale much I’m only measuring clothing fit because that’s what matters most to me but scale comparisons will tell you how close your tracker is.

Here’s the deal though: people burn more calories than they think they do. Only lean, shorter, non-muscular people burn under 2,000 calories a day. I’m 6’ 2” and my BMR isn’t around 2,800-3,000 depending on the formula used (I’m a big guy too) and ANY activity during the day pushes that number up. If you work on your feet some then you may be walking a mile or two a day without realizing it. That makes a big difference daily. If you’re more muscular and taller, that ups your metabolic rate naturally. Adding a 2 mile walk to your routine will probably add maybe 200 calories burned over your standard day, and this adds up over time. If you don’t use a scale to weight yourself, just make sure you build in a error factor. The worst case isn’t that your actually burn what your tracker says you do and you’ll be surprised to lose weight faster. But nothing sucks more than working for 3 lbs off once a week to see that you only lose 1.8. 

[SunsetRunner]

I see a weight loss doctor once a month. I told her about my new fitbit. She suggested that I remove 33% of my weight for the device, as they are all off, no matter what tracker it is. So, for my fitbit app, I removed 33% of my weight, and I have my normal weight set in my food tracker app. So, since I'm 284 pounds, my fitbit has me at 197 pounds. My doc says that my device will be a bit more accurate for me. After trying this out for 3 months, I would have to agree with her.

When I had it set to my normal weight, each workout, it told me I was burning close to 1500 calories (1.5 hours of weights and cardio). No way was I burning close to that amount.

with the adjustment, I'm burning more like 600-800 now, and that feels about right.

Even so, everything isn't exact anyway, not even the calorie numbers on the food labels. Everything is off. At least that's my take on it.

[Anodyne2k]

Yeah you can drop the weight in your tracker so it is more strict for calorie burn naturally. However 33% is extremely inaccurate and doesn't reflect the somewhat slim number of clinical and side-by-side tests done with the Charge 2, Alta, Apple Watch, etc. and a metabolic analyzer. I've seen the Fitbits with HR monitors (which are quite accurate, >5% off on average) under-calculate calorie burn or over-calculate. There's a couple things that people need to consider when trying to use the calorie burn tool to compare calories in vs. calories out:

1) Fitbits will inaccurately count step when you're driving in a car. If you have a smooth suspension system that doesn't jolt the vehicle around when bumps or dips are driven over, you won't have many/any falsely-recorded steps. If you have a longer commute, it's likely that you're going to get a few wrongly-reported steps so you can go into your Fitbit App and do a manual activity log (usually through the "+" button near the bottom of your screen when viewing the app). I do a lot of driving for work so I can end up with 500-1000 steps recorded that I never took and that throws off calorie estimates. Logging a "driving" activity for the time I knew I was on the road adjusts that and keep it honest.

2) Fitbits average ~13-15% inaccuracy in calorie burn reporting. This can be OVER or UNDER, so a 33% pullback in weight is aggressive. Because everyone is different there is no way to be sure about anything when it comes to these trackers because they're worn on the wrist (which isn't ideal for fitness tracking) and the input measurements can't be more specifically applied to you or these trackers might be less than 10% inaccurate (which is an acceptable margin for error). If you're someone that feels better about seeing a good number it may not be ideal to misrepresent your body weight by that margin because other clinical studies would suggest that's going too far in the opposite direction.

3) Don't bother adjusting weight, just do math. I personally wrote out a simple Excel spreadsheet that I use to see what my history is with calorie deficits, daily weight loss (in pounds), with a monthly and all-time overview (for the year anyway). I take away 20% now instead of 11-13% because I knew I may not be losing .6 lbs most days and averaging 2.8-3.5 lbs. per week because I'm not doing a lot of intense exercise and weight lifting. I'm just getting my steps in through more walking and some mild jogging here and there. Since 20% is the average calorie miscalculation I can just take Fitbit's calorie burn and multiply it by 0.8 and I get my realistic calorie burn. It's important to note that people that are heavier may be closer to the true number because their bodies are working quite hard to exercise and most of these error tests that are available online are done on fairly healthy people so there's no telling whether Fitbit's algorithms work better for very overweight people or if it's consistent regardless of body weight/shape.

In the end, the idea of the tracker is to get you moving. Your 33% is aggressive but if you still find motivation from that then do it. It's about what you're willing to accept without feeling like all is hopeless. Day to day weight loss is also something not to get wrapped up in. Losing 4 lbs per week is awesome but the eating habits are hard to sustain for a lifetime and that's why doctors recommend 1-2 lbs per week because the weight loss might be slow for a very obese person but they don't feel like they're cutting off food intake or setting goals so strict that a minor misstep destroys the day. I personally average between 2.25-2.75 lbs. per week right now (goal is to lose 100 lbs. over 10 months and I'm about 7 week in) and I will say that it's nicer being able to know I'm making progress and that in the next year I'll be where I want to be without being insane with my diet and exercise regimen.

[SunsetRunner]

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@Anodyne2k wrote:

Your 33% is aggressive but if you still find motivation from that then do it.

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I went by my weight loss doctors recommendation. She's pretty up on all these trackers and how cardio machines calculate calorie burn.

Plus, She did an extensive "run of the numbers" on my log from the month of April 2018. This log consisted of my daily calories and my exercise info through the whole month. With my recent loss of 136 pounds since January 2017, she did some math and some educated guess work (her being a professional, and bariatric surgeon), she came to the conclusion that even though I am currently 284 pounds, my body is probably at the metabolism level of a 190 pound person.

So, with taking off .33% of 284, I came to 197, which is about what she says I'm at metabolism-wise. And, the fact that everything she has guided me on over the last 15 months has worked for me, I think she's been pretty accurate.

There is just no way I burned 1400-1600 calories during a 1.5 hour training session of weight lifting and cardio being at 284 pounds that my fitbit says I do. And I work pretty intensely too, but it seems hard to believe that is an accurate number.

I'll stick with her recommendation.