Heart Rate/Calorie Burn Fitbit Paradox

jeichelb83

Hello MFP users,

I've been on here for about three years now and have lost about 40 lbs (from 148 to 110ish) so I know how to lose. I've just did some personal research as something just does't make sense to me.

I've been using a Fitbit (Charge HR I believe) and the calorie burn always seemed to be on the high side (I now only take a third of what it give me) but I've been semi-accurately predicting gains/losses until recently. It seems like I burn more with less effort than steady cardio at a slow pace than if I run or do HIIT cardio at more vigorous paces? This goes against everything I thought I knew. As I understood, higher heart rates burned more calories as long as you could safely sustain them.

Example: I'd walk on a treadmill at 3 MPH for fifteen minutes and it'll say I burned 160 calories. Then the next day I'd try a HIIT circuit on higher/lower speeds for the same amount of time, work up more of a sweat and it'll only say I burned 180 calories. It seemed like a lot more work for 20 calories.

Anyone else experience something like this or is there a trainer/expert out there that could explain this?

MelanieCN77

Our devices are fairly limited as to what they can really track and outside of heart rate and steps, they just don't really know what we are actually doing. I have a similar dilemma, in that I skate roller derby but the action is smoother than steps so I don't get a big exercise count on my Apple Watch (or my Fitbit, previously) even though I am sweating and speeding around and getting a good workout.

NorthCascades

Intervals means you're going back and forth between short periods of full effort, and periods of rest or active recovery. If you actually add up all the time you're at full effort, it isn't that much. That's why the calorie burn isn't that much greater. Intervals can be a good way to improve your fitness for racing, but longer exercise sessions at a moderate pace are better for weight loss. Better for fitness for most people, too.

jeichelb83

I was beginning to conclude that as well Cascades, thanks for the confirmation. I think I'm going to keep up the moderate pace until I lose the last 3-5 pounds then maybe switch back when maintaining. Thanks!

sijomial

Bit of a mixed answer here...

In winter I use a sophisticated indoor training bike for a mixture of steady state and intervals work, the calorie estimates come from the power I produce not from HR
Intervals often feel a lot harder, and recovery takes longer, but have a far lower calorie burn. There's a whole load of myths around HIIT since it became fashionable and inflated calorie burns are one of those myths.

If you think of an athletic event where the person who produces the most power wins you don't see them doing intervals.....

Interval training can be really good to work towards your fitness goals though, often as part (not the entirety) of your overall training.

BUT.... Your walking calorie estimate is dreadfully high for only 3/4 of a mile walked! Do you have a particularly high HR during gentle exercise perhaps?

This is a common formula -
Net Walking calories Spent = (Body weight in pounds) x (0.30) x (Distance in miles)

Is your Fitbit working on gross or net calories?

jeichelb83

I believe it's way too high as well, that's why I only take a third of what it gives me. It's a gross number I think because I just turn it on when I'm doing a cardio workout, stop it when I'm done and then it spits out a number that I take a third of and put in in MFP. I don't enter food on the website either so I don't see how it could come up with a net number.

With that formula that's really only about 25 calories for a 15 minute .75 mile walk?

110 x .3 x .75 = 24.75

Now that makes me wonder how I lost any weight all....the paradox continues...

MelanieCN77

How does Fitbit do its math? I know Apple Watch when I set it to "other" gives me credit for that amount of time of "brisk walking." I think that's underselling my skating but also the skating is like intervals, it's like one minute on crazy activity, two or three minutes off, so I try to pause it in big breaks and sometimes just track for half of the hour or whatever. It's not perfect but I have a feel for it.

GottaBurnEmAll

Just an aside... my Fitbit was a little high for me, and I started shortening my stride length in my settings until I started getting burns that reflected what the scale was telling me.

It enabled me to stop playing games with how much of my calorie burn I should be eating or not.

I realize I should have calibrated it properly from the start, but I really... just can't keep track of my footsteps to count them in order to do that. I always lose count.

jeichelb83

Yeah, I always had trouble measuring stride too. I just set it to auto for now to see how that goes. I'm going to give it one more week at the "take a third" level and go from there. If it's still way off I'll drop it to 25%. I'm not able to to use the above formula unless I'm on a machine because I don't think the Fitbit measures distance correctly either.

GottaBurnEmAll

jeichelb83 wrote: »

Yeah, I always had trouble measuring stride too. I just set it to auto for now to see how that goes. I'm going to give it one more week at the "take a third" level and go from there. If it's still way off I'll drop it to 25%. I'm not able to to use the above formula unless I'm on a machine because I don't think the Fitbit measures distance correctly either.

It measures distance based on stride length. If your stride length is wrong, distance will be wrong too. If it has you going much further than you actually do, shorten your stride length until the distance matches up.

You can measure the distance you've actually traveled by using this site:

https://www.plotaroute.com/

jeichelb83

Cool site, I'll have to play with it later. I'm going to keep a closer on eye on stride/distance as well. Thanks!