Question about ftbit charge exercise and calories burned

[Haydensmom]

I used my fitbit today while walking 4 miles. I set the timer on it so that it could record the time walked vs. my heart rate, I don't know if this is accurate, it stated that I burned 677 Calories in 83 minutes. Is that possible? By the way, I am a female, 40 years old and weigh 205 pounds (I don't know if you needed to know that) I spent 74 minutes in fat burn and 43 minutes in he cardio zone? That math just doesn't add up. I am guessing that I didn't start my timer on my fitbit when I actually started my walk. I started it about a .25 mile down the road.

[Haydensmom]

I used my fitbit today while walking 4 miles. I set the timer on it so that it could record the time walked vs. my heart rate, I don't know if this is accurate, it stated that I burned 677 Calories in 83 minutes. Is that possible? By the way, I am a female, 40 years old and weigh 205 pounds (I don't know if you needed to know that) I spent 74 minutes in fat burn and 43 minutes in he cardio zone? That math just doesn't add up. I am guessing that I didn't start my timer on my fitbit when I actually started my walk. I started it about a .25 mile down the road.

[FitBeforeFifty]

Based on your stats, the standard METS value for that walk would be 435 calories. The reason it is logging it higher is probably because your HR was very high -- which may be inaccurate.

I have a fitbit charge HR as well. When I first got it I compared the HR on a run to my garmin HR chest strap and it was fairly accurate. On my run today, however, it was way high and thus gave me an elevated calorie burn. I'm not sure if it was sweat or if the sensor was dirty. I cleaned it afterwards and I guess I'll see if it's better on the next run. Of course I know what my HR should be for a given run (I've been running for years with a HR monitor), so judging the accuracy for you might be challenging without a basis.

What was your average HR for the walk ? Have you walked a lot in the past or are you just starting ?

[Dominique]

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@Haydensmom wrote:

(I don't know if you needed to know that)

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Actually, we’d also need to know your height, since the standard formula (Mifflin St Jeor) for calculating your basal metabolic rate (MBR) uses: sex, age, weight and height. 

Use this online calculator to determine your BMR. Divide by 1440 to obtain your BMR per minute (there are 24 x 60 = 1440 minutes in a day). Multiply your BMR/minute by 83 (duration of your walk) and by 4.3 (METs for walking at 3.5 mph, as per the Compendium of physical activities referenced in this post). See if it comes close to what your Fitbit Charge credited you with.

[Haydensmom]

I'm a female, 5'6, 204, 40 years old.

[Dominique]

OK, your (calculated) BMR is 1612. BMR per minute is 1.12. In 83 minutes, you would burn: 1.12 x 83 x 4.3 = 400 calories (assuming walking at 3.5 mph is 4.3 METs). It’s quite a bit lower than what your Fitbit told you. Remember tracking calories burned isn’t exact science (see this link).

[Haydensmom]

Does the 18 floods I walked be possible to contribute to those calories?

[Lily-Mari]

you may not have started the timer at the same tiime that you started the walk and based on your health your heartrate may be unnaturally high which would influence the tracker thinking that you were burning more calories.

[Lily-Mari]

i think that it is most likely that you just have a high heartrate.

[Haydensmom]

My resting heart rate is 56

[Dominique]

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@Dominique wrote:

OK, your (calculated) BMR is 1612. BMR per minute is 1.12. In 83 minutes, you would burn: 1.12 x 83 x 4.3 = 400 calories (assuming walking at 3.5 mph is 4.3 METs). It’s quite a bit lower than what your Fitbit told you. Remember tracking calories burned isn’t exact science (see this link).

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Actually, your average speed (4 miles in 83 minutes) was 2.9 mph, not 3.5 mph (as I worked out quickly out of my head). The METs for that activity are correspondingly lower (3.5 instead of 4.3):

Your relatively low resting heart rate wouldn’t affect calories burned during activity IMO. However, your relatively high heart rate during activity could possibly trick your Fitbit into thinking you burned more than what the standard METs would predict.

You may also want to repeat the experiment: perform and record the same activity (same distance, same time) and see whether you consistently get the same numbers.

Anyway, regardless of what Fitbit said you burned, some activity is better for you than no activity at all, so just keep moving!

[Dominique]

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@Haydensmom wrote:
Does the 18 floods I walked be possible to contribute to those calories?

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You probably meant "floors". The standard METs I gave you assumed walking on a flat surface. If this is not the case (as suggested by the number of floors you were credited with), you would burn more.

Anyway, for weight loss TDEE (number of calories burned during the day) is more important than calories burned during a single activity. If you wear your Fitbit 24/7, you should get a relatively accurate TDEE. Eat less than that during the day and your weight will start to come down.

[Haydensmom]

Lol. Yes I meant floors.. swipe text is awful..

[Dominique]

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@FitBeforeFifty wrote:

Based on your stats, the standard METS value for that walk would be 435 calories.

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Actually, it’s even less than that, based on the added information (height) supplied by @Haydensmom in the Get Fit forum.

@Haydensmom: please do not start the same discussion in two different forums (such as here: Get Fit and Weight Loss). Pick up just one (the most appropriate) and keep the discussion going on that forum.