Fitbit Surge Caloric Output accuracy.

[andrw45]

Hey guys, I'm a 26 year old male weight approximately 255 pounds 5"10" tall. I just bought a fitbit surge and noticed that my caloric output is notably higher than estimates from my earlier One and Flex Devices. I know this takes into account your heart rate and those devices do not. 

For instance, today I walked just shy of 12,000 steps with 158 active minutes. I was on my feet pretty much all day and every time I checked my heart rate it was upper 90s to around 120 at the highest. So my heart rate was elevated most of the day. Caloric output came in at roughly 4800 calories as of midnight. 

Thats a pretty high number to me. Does it seem like a ballpark accurate figure? Other men of similar height, weight, and age, feel free time chime in and compare numbers. 

I put this in the weight loss forum because its not really a issue with the device as much as checking accuracy and comparing with others. And becasue I am trying to lose weight, I need this figure to be as accurate as reasonably possible. 

[GershonSurge]

I have a Zip and a Surge. I wear both of them all the time. The Zip is attached to another account.

I've checked the accuracy of both of them while losing weight and during both high exercise and low exercise periods. I've been nursing an injury for the last five or six weeks, so my recent activity is low. Before this, I was averaging 4,000 calories a day. The way I checked the accuracy was by comparing the total calorie deficit over a period of time with weight loss. I weigh and log all food, so the input was measured as accurately as is possible.

The Zip undercounts calories by about 20%, and the Surge overcounts calories by about 20% during periods of high exercise. They are more accurate during periods of low exercise. The error seems to be in the activity calories. It takes about a 4,200 total deficit to lose a pound according to the Surge and 2,800 according to the Zip. Both are consistent in their measurement error.

On your active day, you likely burned about 4,000 calories. 

The devices don't really need to be accurate. They only need a consistent error. While losing weight, I seldom ate below my Basic Metabolic Rate. At first, I often had a 1,500 calorie deficit according to the Surge. Lately, I've discovered a 750-1000 calorie deficit works just as well. This was likely because my body adjusted its metabolism with the larger deficits. 

[Jeroniymo]

i wold suggest that dies seem high - yesterday i was in the 16000-17000 step range with 140 active mins - i am a similar weight to you though a bit shorter (stride length 68cm).

my overall caloric output for the day was ~3600 using my flex.

It could be that your heartvratevbeing taken into account makes the key sifference, but 4800 seems a lot above where mine put me.

[FitBeforeFifty]

In general, I think fitbits without HR monitors are going to under estimate calories and those with HR monitors tend to over estimate.

I've had my fitbit charge HR for 3 months now. Based on my weight and my food intake, it's over estimating my calorie burn by 700 - 900 calories per day.

[JohnRi]

I'm a couple inches taller than you, and 45 lbs lighter, but I typically burn around 3200-3400 calories on most days.  I walk for 4-5 miles at around 4 mph everyday, and lift weights for about 50 minutes 3 times a week.  I used to burn around 4000 calories when I was a lot heavier.  Back then I was walking 3-4 miles every other day, and walked for around 90+ minutes.

I usually only get 60 active minutes a day now.  Anywhere from 11,000 to 15,000 steps is normal for me.

So did you burn 4800, probably not, did you burn 4000-4800, probably so.  It's in the ballpark.  There is no tracker that is going to be 100% accurate.  But you just need to have a rough idea, so that you can know how much to eat.  Assuming you are doing a 1000 calorie deficit, I would have eaten around 3000 calories the day you hit 4800 on your Surge.

Good luck and keep active!!!

[andrw45]

Thank you for the replies so far. Its interesting to see what kind of results others are seeing. And I'm not counting calories too closely yet, just watching portions, drinking less soda pop and beer, trying to be more active, and drinking more water. At least I'm not gaining anymore.

[emili]

the answer lies "on" the scale. Once you start counting calories in and monitoring calories out- the scale will tell you how accurate you are in your deficit. the scale will tell you what adjustments need to be made. if you are currently not losing or gaining- this means your in is equal to your out give or take a small percent to account for salt, water and waste. the number in and the number out is all based on estimates, it will never be 100% accurate- but it gives you guardrails to stay between so you can lose, maintain or gain. much luck in your journey.. best, E.

[FitBeforeFifty]

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@emili wrote:

the answer lies "on" the scale. .... it will never be 100% accurate- but it gives you guardrails to stay between so you can lose, maintain or gain. much luck in your journey.. best, E.

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While I agree the it will never be 100% accurate, my point is it isn't even close enough to provide guard rails. The HR versions of fitbits way over estimates energy expenditure. I've had my charge HR for 3 months. I've tracked exercise and food intake since June of 2011 using another app, so I have a pretty good idea what my energy expenditure is, based on my ability to maintain my goal weight for 4 years. Before purchasing my fitbit 3 months ago, I used an app that used BMR * 1.45 + ExerciseCalories where ExerciseCalories is based on the METS. Based on my weight and comparing a typical day to my previous estimated TDEE, my fitbit over estimates my TDEE by up to 900 calories per day. A 900 calorie error isn't really useful. I could think I'm eating at a 1000 calorie deficit to lose 2 lbs per week when I'm actually eating at maintenance. 

After 3 months of using my fitbit to estimate energy expenditure, I think I'm just going to disconnect it from my calorie tracking app and go back to my old way of estimating energy expenditure. 

[andrw45]

I don't like the idea of up to a 900 calorie overestimation. I'm considering taking it back and exchanging it for a non HR Charge or Alta. Half the cost and more useful data. I'd rather have it slightly underestimate calories burned than overestimate by up to 900. I bought this thing specifically to track my bike rides and runs but if it won't give me an acurate estimate of calories burned or even my heart rate, I can't really trust it. I could just use the S Health app to track my rides and runs and then manually log the data in the fitbit app or online.