# Cronometer Estimates Custom BMR based on actual observed data

I use an activity tracking device (Garmin watch) to capture my calories burned (specific activities, Daily Activity) and I regularly enter my weight.

Thus Cronometer should be able to provide a custom BMR by totalling up calories consumed, calories burned, and weight change over some particular time period. (I downloaded data and did this in spreadsheets as a proof of concept.)

Yes, I could use the number I calculated as a Custom BMR, but I expect that it will change both seasonally and as I age. It would be great if I could just ask Cronometer to look at, say, my last 3 months of data and calculate the BMR to use in displaying my daily calorie requirements.

(If this is not a new request, feel free to close it and just move the text into a comment for the relevant feature request.)

• That's a neat idea! I'm curious how different was your calculated BMR from the one estimated by Mifflin St. Jeor?

I had my energy expenditure measured years ago by indirect calorimetry in an experiment I volunteered for at university. It was bang on the predicted value for my age, height and weight at the time. I'm not sure why, but I did think I would find something different.

Karen Stark
cronometer.com
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• Mifflin St. Jeor estimates 1456 kcal for me. My computed daily metabolic (non-activity) calories required was 1696 kcal. (Thus, 240 kcal difference.) So the Activity Level adjustment of "Sedentary (BMR x 0.2)" which adjusts by 291 kcal is not too bad of an adjustment.

Note that I don't wear my Garmin watch while sleeping, so my imported Activities won't capture anything that might qualify as a non basal metabolic activity during sleep periods. But I think that should be really minimal. Also, of course, Garmin is undoubtedly mis-estimating kcal burned in my activities. But a dynamic BMR estimator based on reported activities should just gracefully handle that, assuming consistency in reporting.

• I actually think that's a neat idea, especially as a professional data nerd. If Cronometer has all of your weight, activity, and food data should be able to tell you, with a reasonable guess, what your actual BMR is, at least in relation to the accuracy of your tracking devices and your food tracking. Even without a tracking device it may be able to give you a better number that way. This could also help adjust for error in a given tracking device, as long as it's consistently inaccurate the same way. Over a long enough period of time it should be able to handle small day to day variations like water weight.

I've found different services can give you pretty significantly different calories values for your target. Cronometer tends to be the lower and probably more realistic value.

I could see this maybe even being like a cool Gold option with a toggle for something like "Use Historical Estimated BMR" or even something like "Use Historical Estimated Calorie Goal" if you don't want to be claim to be estimating BMR or something.