Accuracy of Fitbit calories burned

The calories you burn account for the energy it takes for your body to function. When you walk or exercise, it adds to it. Our numbers are about the same (height & weight) and I have mine set at a 750 calorie deficit for the day. When I workout, my deficit ends up being at least 1000.

I have the surge, and it drastically over estimates my calories... but that's with the hr most likely going crazy during lifting which it's not designed for.

My One seems fairly accurate. (No experience w/ the wrist models.) When I hit maintenance weight, I learned that if I ate below my TDEE according to Fitbit that I continued to lose weight.

Fitbit cals burned are all day/TDEE including BMR. Not just for exercise/miles walked. Example I'm at 1299 right now, 6:50 pm. Its not 1299 'exercise' but 1299 total from all sources.

PS cals burned for any activity will depend on the person's stats. And for walking, also incline or not. A mile at 4mph for me is only about 75.

mommazach wrote: »

102 Calories burned in a mile for walking 4mph. You'd have to walk about 19.6 miles to get the 2,000 calories burned. I'd start checking the app settings for walking, or use another app like Map my walk, to get a better idea of the actual calories also. Don't give up on your Fitbit, but don't think of it as the most accurate measurement you can.

I have the fitbit zip, as the only exercise i do is walking, so a HRM would be a waste for me.

Yesterday I did 21,621 steps (10.6m) and fitbit estimated my TDEE at 2,706... So yeah... Can't say I 100% trust it.

StaciMarie1974 wrote: »

That is VERY active. What is your BMR?

Christine_72 wrote: »

I have the fitbit zip, as the only exercise i do is walking, so a HRM would be a waste for me.

Yesterday I did 21,621 steps (10.6m) and fitbit estimated my TDEE at 2,706... So yeah... Can't say I 100% trust it.

According to Scooby workshop, and lightly active, My BMR is 1424- TDEE 1979

jeepinshawn wrote: »

Christine_72 wrote: »

StaciMarie1974 wrote: »

That is VERY active. What is your BMR?

Christine_72 wrote: »

I have the fitbit zip, as the only exercise i do is walking, so a HRM would be a waste for me.

Yesterday I did 21,621 steps (10.6m) and fitbit estimated my TDEE at 2,706... So yeah... Can't say I 100% trust it.

According to Scooby workshop, and lightly active, My BMR is 1424- TDEE 1979

If you are walking that much everyday you are more than lightly active Imo

I try to get there everyday, but there are days like today when I've only done 12,000 steps. So the low days balance out the higher days

From December 2, 2014 to October 7, 2015, a period of 309 days that saw me moving from 224.7 lbs to 169.7 lbs and performing a total of 5 DXA scans, using the assumption that 1lb of catabolized lean mass is 1500 Cal and 1lb of fat mass 3500 Cal, ignoring <0.4lbs of bone mass changes, and making the assumption that my MFP logging is 100% accurate (which we KNOW it cannot be), that DXA scans are 100% accurate (fat % can be +/-1% from what is calculated) and assigning ALL discrepancy between expected and actual loss to Fitbit's TDEE calculation, the Fitbit started the time period by under-estimating TDEE by 0.5% and ended the time period over-estimating TDEE by 5.5%. Each scan showed a progressive increase to the over-estimation.

These observations tend to confirm my belief that there is a degree of adaptive thermogenesis and increased adaptation to exercise that has taken place as weight loss and deficits have persisted.

It also tends to confirm my belief that for all intents and purposes the bloody Fitbit (in conjunction with careful MFP logging) is remarkably bloody accurate if you are not an outlier.

So, to start, and absent your own data, just assume the darn thing is accurate! You paid good money for it, give it a chance!

Use a trending weight program that should probably be www.trendweight.com since you are using fitbit.com and can automatically connect the two accounts in less time that it took you to read this post.

Every month or so, compare your trending weight to your expected weight loss for the time period (hint click on your fitbit.com profile pic and look at the calories in-calories out graph for the past 30 days) and adjust your expectations and/or your deficit based on the results you've observed!

(and watch out for days where MFP-Fitbit integration isn't working and you have to manually correct wrong entries)

And while you're at it OP: cut your deficit to 500 Cal as you are currently cutting way more than 20% of your TDEE.

ETA: while obese I was aiming for a deficit of 25% of TDEE (and achieving slightly less than that). This was tapered to 20% when I became overweight. Since July I am aiming for a deficit that is closer to 10%. Note that my TDEE during the 10 months in question ranged from just over 3500 to just over 3100.

I had the HR for about 9 months before I upgraded to the Surge. I found the HR pretty accurate, but when I did sports that involved using my hands (skiing, horseback riding, even hiking...most sports apart from running basically), it underestimated the calories burns. I use a H7 Polar belt now for everything apart from running/walking.

PAV8888 wrote: »

a period of 309 days that saw me moving from 224.7 lbs to 169.7 lbs

Impressive!

synacious wrote: »

I find that my Charge HR is accurate. I think for some people, not all, they find it inaccurate not because the calories are too high, but because they think they're eating the calories Fitbit says they can, but they're not. Without a food scale it's all just even more estimations on top of the Fitbit calorie estimation. So if they're trying to take advantage of every last calorie, they may actually be going over by several hundred.

Anyway, I think people can underestimate their level of activity too. 20K steps and up will never be lightly active. 10K is already lightly active. Most people, especially in the US, get no more than 5000 to 8000 steps per day. THAT is what sedentary is.

Based on currently available evidence, we propose the following preliminary indices be used to classify pedometer-determined physical activity in healthy adults:
(i). <5000 steps/day may be used as a 'sedentary lifestyle index';
(ii). 5000-7499 steps/day is typical of daily activity excluding sports/exercise and might be considered 'low active'; (iii). 7500-9999 likely includes some volitional activities (and/or elevated occupational activity demands) and might be considered 'somewhat active'; and
(iv). >or=10000 steps/day indicates the point that should be used to classify individuals as 'active'.
Individuals who take >12500 steps/day are likely to be classified as 'highly active'.
http://www.ncbi.nlm.nih.gov/pubmed/14715035

My own observation of the correspondence between MFP and Fitbit is:
MFP Sedentary: 3500 to 5000 steps
MFP Lightly Active: 5000 to 8000 steps
MFP Active: 8000 to 12500 steps
MFP Very Active: 12500 to 15500 steps
Exceeds MFP Very Active: above 15500 steps

My own experience with Charge is that it's fairly accurate. It gives me ~500 calories for an 7 mile run. I've been eating all the FitBit calories and I've been maintaining for a year now.

I walk an average of 25k steps daily ( I typically do high stepper challenges ) and I have been nervous about eating my fitbit calories because they're so high, however I est most of them, if not all at times and have been losing. Slowly but losing. On my rest days, which I tend to average about 12K steps I burn around 2500 or more. I have only had my charger hr since Christmas but I think it's fairly accurate. I am also into strength training and I am not sure how that influences things.

When I had the Zip, it tended to UNDERestimate. For reference, all my cardio was step based (light jogging/walking), and I ligged strength training through manual entry. I told it I was 5 inches taller (but kept stride length true to resl life) to make it accurate for my personal experience.

Then I traded up to the Charge HR. In the year I've had it, I've found it much closer to accurate. I've only made a 1inch adjustment. Seems spot on, more or less.

PAV8888 wrote: »

Fitbit seeks to encourage people to move more.

The basic Fitbit formula ought to under-estimate most people for whom Mifflin St Jeor holds true. Fitbit assigns straight BMR to any time period it doesn't detect movement. If you look into the MET tables, this is an under-estimate as many non movement generating daily living activities would get you MET 1.3ish. In fact, if you factor in corrected METs this could be even more for many people.

So yes, Fitbit gives you perhaps a little bit more than straight MET value for your walking; but, it tends to average out JUST FINE because most people have way more periods of low activity than periods of high activity during their day

In any case, there is a heck of a lot of difference between I need to run a 1%, 5% , or even 10% correction to my Fitbit TDEE estimate, and OMG I can't trust the calories my Fitbit gives me, I don't eat any of them back (or even I eat 50% of them back given that a Fitbit TDEE adjustment is not a true exercise adjustment and should not be eaten back at only 50%.)

For most people we are discussing a sub 10% correction which would be smaller than the total deficit/surplus they are running. And if you connect Trendweight to Fitbit, reviewing how far off your logging is from your expected results is relatively easy!

Of course, as already mentioned, the quality of your food logging also matters: if you are 20% too low when it comes to recording your food intake... yes, Fitbit will "overestimate you".

Like many things in life: trust AND verify!

Yes, this is true. For me, I think the difference is up to about 8-9% a day, and a lot of days I happen to fall a bit short of what it says anyway without really making an effort.