I've got a lot of experience counting calories and observing my weight changes over time. I'm pretty consistent with it and can usually guess my daily consumption within 500 calories or so, especially if I'm eating foods I'm accustomed to. Suffice it to say, I can tell the difference between a 3000 and a 5000 calorie day. It seems Fitbit can't.
I got a pixel watch yesterday, and while it's been a great smart watch, I'm surprised by its calorie estimation algorithm. Today I went for a 5 mile run in 45m or so and did a CrossFit workout, which was about 40m of low intensity warmup and cool down plus 20 minutes of high intensity cardio and weightlifting. I also did some mild walking about and a dance lesson, none of which really got my heart rate to the level where I felt like I was working. But it would boost calorie burn somewhat. Fitbit figures I burned 5200 calories today. I know this includes BRM (as it should) and, yes, I did set my demographic info correctly. To put it in perspective, I've been wearing a Garmin Epix or Fenix for years and my Epix estimated today at 3600 calories (I wore both to see how they'd compare). I didn't wear the Garmin for the "not serious exercise" portions of the day though, so Garmin might be 200 or 300 lower than it would be if I'd work it all day long. From experience, I'd figure If I ate 3250 calories a day and did this volume of exercise, I'd lose about a pound a week. If fitbit's number was accurate, I'd be losing more like 3 pounds a week (an unhealthy/unsustainable rate of weight loss).
Anyways, this Fitbit number is just so wildly high as to be completely useless for any kind of weight management use. I donno if it's just inaccurate or deliberately inflated to make people feel better about themselves, but it can't possibly be this high. The only days i ever had 5000+ calorie days in Garmin were when I hiked 17 miles with a 65 lb pack on. And that was nearly 8 hours of hard work, not less than 2.
All this to say, can I calibrate it? Ideally I'd love to be able to log calories for a few weeks along with weight and have it calibrate itself based on weekly average weight. But, if nothing else, it would be nice to be able to adjust the BMR and maybe have it multiply the active calorie burn by some factor to fine-tune the result into something that is within the realm of possibility.
