Charge HR calorie burn UNDER estimation?

UncreativeMe123

Have any of you had any suspicion that your fitbit's were underestimating calorie burn? I wear a Charge HR almost all the time (except of course swimming, in which case I use their website estimator), and I lost weight really fast and got to my goal weight using their calorie estimates. Twice this week I seriously binged and didn't gain weight, and am wondering if the route of the binge urges might be because of calorie underestimation.

editorgrrl

I have a Flex, not a Charge. I've been in maintenance for 8 months, and have gone over goal every week. I've lost 4 more pounds.

We should all be looking for the maximum number of calories at which we lose weight or maintain—never the minimum.

NancyN795

From what heybales has said - and it makes sense to me - FitBit is generally going to underestimate calorie burn by a little. It counts all inactive time as burning calories at your BMR, but in reality, if you're not asleep, you're burning more calories than that, even if you're not moving much.

However, weight can fluctuate for a lot of reasons, so those two serious binges could end up showing up later, when you least expect it. You may have lost some water weight that offset the extra calories temporarily, but will be back. Not that I have anything against a good binge now and then. I'm just aware that if I chose to indulge, I always have to pay for it one way or another.

It has been almost a month since I started really trying to test how close my FitBit's calorie estimation is for me. So far it seems to be darn close but maybe underestimates a little. However, going by your profile picture, you're much younger, and much thinner than I am, so you could be quite different. The only way to really know is to track what you eat very carefully for several weeks. I resisted doing that for a long time.

heybales

UncreativeMe123 wrote: »

Have any of you had any suspicion that your fitbit's were underestimating calorie burn? I wear a Charge HR almost all the time (except of course swimming, in which case I use their website estimator), and I lost weight really fast and got to my goal weight using their calorie estimates. Twice this week I seriously binged and didn't gain weight, and am wondering if the route of the binge urges might be because of calorie underestimation.

If you didn't have much to lose, and were eating at decent level prior, a healthy body can take a short big deficit, or surplus, and deal correctly with it.
So it appears it didn't slow down on big deficit, so you lost fast. If you had more to lose you'd probably discover the body will eventually adapt and slow down.
And when you ate in surplus, it sped up to deal with extra calories.

Good job.

If you are still in diet mode, time to come out.
Also realize the device is estimating calorie burn only during the workout outside of daily steps.
When eating at maintenance and doing really hard workouts that require a lot of repair from - it has no clue your metabolism went up for hours on end. If lifting, that repair can take 12-24 hours.
- You will burn more than that is unaccounted for.

It's why many using the devices go in to bulk mode lifting, trying to gain muscle. They'll eat 500 more daily.
And discover they don't gain 1 lb weekly, if any, for many many weeks.

jaydotch

Just got my Charge HR yesterday and went on a usual 3mile run and it calculated I burned 385 cals or so where my usual RUNKEEPER app estimates I burned 480 during the same period/pace. I didn't click the activity tracker on my Charge though (referring to holding the button till the timer comes up) Not sure if that makes a difference.

NancyN795

jaydotch wrote: »

Just got my Charge HR yesterday and went on a usual 3mile run and it calculated I burned 385 cals or so where my usual RUNKEEPER app estimates I burned 480 during the same period/pace. I didn't click the activity tracker on my Charge though (referring to holding the button till the timer comes up) Not sure if that makes a difference.

If you didn't create an exercise record (by holding the button, or by entering the time and duration later), how do you know what your FitBit calculated for the run?

Still, I believe you when you say that your Charge HR estimated a lower burn than RunKeeper. Mine usually estimates a lower burn than Map My Walk. I keep the FitBit number.

If you put your Charge HR into exercise mode for your run then it will guaranteed use heart rate data, rather than step data, to calculate your calorie burn and it will take more frequent heart rate readings. So, it will probably be more accurate.

Plus, exercise mode it makes it much easier to compare not only calorie burn, but distance. You should check to make sure it has a roughly correct stride length. Heybales has good instructions for that in his FAQ. I don't have easy access to a treadmill, but over time I've gotten mine better just by comparing the FitBit distance to the Map My Walk distance and tweaking it. Stride length probably doesn't affect calorie burn calculations as much for a Charge HR (or Surge) as it does for the other FitBits, but I think it is still better to calibrate it.

You just got your FitBit, so give it a few days to "learn" your patterns. Then, for several weeks (at least), log your food carefully and compare what FitBit predicts you should have lost with what you actually lost. The only way to really assess whether it is estimating accurately is over a longer period like that. On a day-to-day basis our weight can fluctuate for many reasons, but over the long term it responds to a calorie deficit (or surplus) in a predictable way.