Calorie Burn Rate Formula Needs Adjustment

[Oriondestiny]

I've been doing a basic calorie in - calorie out diet where I eat less than what my Fitbit Charger 6 shows I burn every day. I've been doing this for 4 weeks now and lost 5 pounds. Fitbit knows my age, weight (I input daily) my heart rate, resting heart rate, activity and steps. With my weight down 4% and my resting heart rate down a good 7%, I would expect my calorie burn rate to drop as my body compensates for the lower calorie intake. I should see this in the hourly BRM calorie burn during the night while I'm sleeping which for me is still 56 calories per hour. This tells me that resting heart rate or heart rate is not calculated in the calorie burn. The other factor that should affect calorie burn is that I'm carrying around 5 less pound all day long while I'm  up and moving. You can see my Fitbit daily calorie burn, while up and down would average the same. It would make sense that if your carrying around less weight, you would burn less calories and if your heart is beating less during down times where your sleeping and sitting, your burning less calories. You can see the affects on my weight loss as time goes that I'm losing less each day on average by the arc on both average lines. It is obvious my BMR has dropped from dieting and the more weight I lose, the harder it is to lose, and of course, keep it off. I've both decreased my metabolism and from dieting, increased my insulin sensitivity from exercise so I'm primed to gain all that weight back fast, which is natural. Back to the point, they need to fix their calorie burn formula and add these other factors in. My Fitbit should be showing my calorie burn going down with my weight and heart rate and be showing the calorie out red line dipping down to the 2000 range with the same amount of activity. If I keep eating as little as I am, at some point the blue and red line should meet. I can only lose so much.

First chart is calories in and out, 2nd - weight loss graph, 3rd - Heart rate:

[Rich_Laue]

Does fitbit know your current weight, age, height, gender, etc 

If not, then it probably is wrong 

[mUNDh]

Orion you speak as an engineer: long sentences, full of details, long message.

Basic idea:

- you input all data, including your In Calories,  

- you see changes in heart rate, weight,

- Fitbit calculates your burned Calories like nothing happens with your body.

Yes, welcome to the world of Fitbit: looks great on paper that it calculates your burned calories. This sells. 

To me it shows i am burning 4000 Calories/day with amateur like exercise for some 100 Active minutes / day.  Imagine my surprise.

[LZeeW]

@Oriondestiny   Here is some basic Fitbit information and some observations.

• Fitbit uses the Mifflin St Jeor equation to estimate your BMR.  It uses your age, sex, height, and weight.  Resting heart rate isn't used in the equation.
• Your five pound weight loss (basically 130 to 125) will change your BMR by about 20 calories per day or less than 1 cal/hr.  This might explain why you don't any difference in your calorie burn graph.
• You are mentioning things like insulin sensitivity, but this is seen in more dramatic weight loss.  Insulin resistance with a normal (or low) body weight can occur in some ethnic groups.  Your profile picture isn't one of them.  Your 5 pound weight loss most likely hasn't change your insulin resistance.
• You are making incorrect conclusions that your calorie burn should have changed because your resting heart rate is lower.
• Your comments about how hard it is to lose more weight after some loss become important with more dramatic weight loss.  Again, probably doesn't apply to you.

There are several widely known equations to estimate BMR.  Mifflin St Jeor is widely accepted as giving a better estimate over a wide range of body types.  Fitbit uses proprietary, heart rate based algorithms to estimate activity calories.  They are estimates.  Fitbit only needs to change its BMR calorie burn when a better equation comes along.