I wear a Fitbit that tracks my heart rate. I’ve been really stressed recently which is causing my heart rate to spike at times. When this happens, Fitbit tells me that I’m in the “exercise zone” and that I burned a ton of calories. I’m assuming this is because my heart rate falls into the exercise “fat burn” zone, but does my body actually burn any more fat than usual if I’m just sitting at my desk and anxious? Seems way too good to be true…
In: Biology
At some level, sure. Takes more energy (calories) for a heart to beat more times per minute than less times per min.
Your watch should use the heart rate, and motion (and maybe galvanic skin) to determine how many calories you are actually burning. But yes, Sitting on the couch at 40BPM burns less calories than sitting and doing 100 BPM (all other things being equal).
No, the calorie calculations are assuming that your heart rate is rising due to movement of your muscles.
Emotional stress is just strain on your organs.
Lets say you go for a run. Running uses (mostly) your leg muscles and they need to consume more energy. Your heartrate increases to supply more blood to allow the muscles to consume more energy. A vast majority of the energy (calories) burned is from your leg muscles, but a small amount is from the extra energy used by your heart to pump blood.
If you are stressed out then technically you are burning that small amount of extra energy from your heart, but you are burning way less than you would exercising. Your fitbit does not actually measure how much energy you use. I don’t know what all sensors it has, but my guess would be that it only measures heartrate and it can’t tell why your heartrate is increasing and so it just assumes it is because you are exercising.
You’re burning more calories than if your heart was at rest. You’re only burning fat in a calorie deficit. You could be in a calorie deficit even if your heart rate was at resting by eating less calories than you burn.
Another tidbit is that when ur more stressed & hr goes up ur body produces more cortisol which (my understanding & I can be mistaken of course) signals ur brain to acquire carbs. I have found when I get the high hr due to stress, if I take a run up & down the stairs or 5 min jog, it’s like my body recalibrates. Issue is stress makes you not want to do a damn thing so I have to fight to build that habit.
A little. Your heart is a muscle that physically requires energy to work so it does burn more when it’s beating faster. But it is nowhere near what you burn during exercise where you are working major muscle groups. so in this scenario, your Fitbit is not going to give an accurate picture of how many calories you’re burning. It assumes you’re working out your body based on what your heart rate is.
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