Calories burned as it relates to caffiene and other thermogenics

[Zak151harry]

I understand how a fitbit estimates calories burned, but I'm not sure if stimulants that raise heart rate also raises caloric burn proportional to the increase in heart rate. For example if I walk on a treadmill at 2 mph for 30 minutes without having caffiene, my heart rate will be lower than if I had the pre-workout caffiene. However, if my heart rate is elevated it increases the fitbits estimation by a considerable amount. My heart rate can be up to 20 bpm faster at the same METs, so I'm curios if that artificially elevated heart rate is also artificay inflating calories burned, it seems to me that it would overestimate. 

[LZeeW]

Hello @Zak151harry and welcome to the Community.  Your Fitbit calorie burn is heart rate based.  So yes. that calorie burn is falsely elevated.  The key word is estimation.  Your Fitbit isn't a scientific instrument.