Fitbit Surge Calorie Accuracy

Are these your adjustments on MFP or your reported exercise burns for the day per Fitbit?

Then that is the difference between your Fitbit Total Calorie Burn for the day and what MFP thinks you burned. Your Fitbit calorie burn accounts for BMR+daily activity in the form of steps + workouts
Fitbit Total - MFP estimated based on activity level setting = adjustment
If you click the little "i" next to the adjustment it will show you the math (website).
On the phone app - tap fitbit adjustment and then tap earned calories to see the math.

If you are getting extra calories on a day without exercise, then you likely have your MFP activity level set to low.

The only way to really know if your Fitbit Calorie Burn is accurate for you is to trust it for a couple weeks and see what happens to your weight. In a couple weeks compare what happened to your weight, how much you ate, and what you expected to happen with your weight. If it all lines up then it's accurate.

All calorie tracking for Fitbits is based on a (seemingly high) calculated BMR (base calories burn for just living and breathing) for the whole day, then the addition of calories based on exercise, walking, and general motion to give you a TDEE (Total daily energy expenditure).

That means it will continue to add calories each minute you are alive, which is why it gives you burned calories while sleeping and such. You may wake up and already have 600 calories burned base on being alive. As you move through out the day lesser Fitbit models base additional calories burned on steps and mileage. Heart rate Fitbits base it on your HR zones and adjust calories burns with that.

All that said, I have had many different fitness trackers. I loved my Fitbit Force. I have had the Surge for some time and I don't think it is nearly as accurate as the Force. Not so much calories burns for activities, which are generally around 15% higher than most online calculations you will find, but more so the general calories added through out the day. The highest calculated TDEE I can find ( http://iifym.com/tdee-calculator/ ), saying I am doing two HUGE workouts a day, puts me at 3100 calories per day. Now, I sit on my but most of the day at a desk, and I do get in about and hour of general HIIT, walking, and strength training, but not nearly two HUGE workouts a day, so I would more likely around 2600 calories a day for TDEE. The rub is, my Surge TDEEs are regularly over 3900 calories, with some topping 5000 calories burned in a day! If I was to eat and operate based on Fitbits numbers, I would be gaining weight like crazy.

I missed the time frame to be able to return it, unfortunately, so I have to work around those ridiculous numbers and reduce everything by around 1000 calories per day. I am still working with Fitbit to help them improve the unit though my situation, but in my opinion the heart rate measuring of Surge or Charge HR is useless and gives terrible calories burns. I am about to turn it off, which irks me because then I have paid $150 extra for what is essential what you get in the $99 Flex - a step and activity tracker.

I switched from a One to an HR a couple of weeks ago. I have not changed my activity level or exercise program since the switch and the HR is giving me an additional 350-400 calories burned daily. I expected that because I felt the One was undercounting the burn for my elliptical time. However, the kicker is that I'd lost 60 lbs in the last 8 months with a strategy of using FB+MFP and trying to hit a 750 daily calorie deficit on the nose. 60 lbs in 35 weeks is 1.74/week so my thinking is that the One was undercounting a bit since I feel pretty good about my calorie counting process. However, an extra quarter pound a week is only 125 calories a day rather than the 350-400 getting added by the One. That fits with my actual experience as I've not really lost anything since I switched 2.5 weeks ago. My experience over the last 8 months says it's too early to draw any firm conclusions but the initial indication is that I need to start under shooting the HR number by at least a couple of hundred calories a day.

I tried the TDEE calculator and the numbers look very consistent with my FitBit numbers early in the day before I exercise so I'm going with the theory that the HR overestimates exercise calorie burn for me by about 20%. But that's for my metabolism, my exercise program, and my diet. The only way to know for sure for you is to run it out for a couple of months and see what the scales say. I'll be watching the results of a daily planned undershoot of 200-300 calories to see if that gets me back on track. That said, there are so many uncontrolled and unknown variables, it's never going to be anything close to definitive.

testtannebil wrote: »

Chaelaz's results are wildly inconsistent with mine so I'm included to think that there's either a configuration problem or a hardware defect.

They have been working with me, but problems still persist. One issue at this point is the accuracy or the built in HR monitor, which does not seem to be working well for me. I've been side by side comparisons using the Surge and my trusty ol' chest strap HR monitor and while my Surge has never peaked over 148, my HIIT session regularly peg me 170+, as they should. The issue is, you can go the the Fitbit forums and find a a good section of people with the same issues.

That said, I am not sure what percentage of people are having issues, so I might just be that exception to the rule.

I'll post if anything ever resolves.

FYI - Fitbit is having me send my unit back for a replacement. HOPING it is just that simple. Will update again when I know.