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jdelasko 08-20-2012 05:30 AM

How does Fitday calculate calories burned vs METS?
Fitday's activity log uses standard MET values that can be found here:

I am wondering what the exact formula Fitday uses to calculate calories burned from these standard MET values. I ask, because the numbers Fitday comes up with, vary dramatically from the results I get from any of the equations presented on the above referenced site. It makes me wonder how accurate Fitday's calorie burn numbers are.... or anyone else's for that matter.

cjohnson728 08-20-2012 01:20 PM

I can't say for sure what formula FitDay uses, but I can relate to the frustration of "how well does anyone know, really." Our body knows for sure and anything else is just a guess.

The longer you follow whatever eating/exercising program you do, and the longer you log, you will get more of a sense of how accurate your numbers here are. There are ways to make adjustments. Some of us find it's more accurate if we log our sleep hours, even though that's theoretically taken into account. You can also customize your metabolic rate and put in the number of calories you think you burn through that.

A year or so ago I did one of those hydrostatic body composition tests and part of the result entailed a printout of the calories burned for basal metabolism. I plugged that value into the customized blank in FitDay. If you have anything like that, or data from a BodyBugg or similar device, that's probably the most accurate you can get, but most of the time it's just a "best guess" anyway.

jdelasko 08-21-2012 04:32 AM

I was hoping someone from Fitday could post the actual mathematical formula... assuming it's not some deep, dark secret. I'm sure it takes into account, age, height, weight, and gender. I'm just wondering what the actual equation is, and where it came from. Some of the formulas to calculate calorie burn from the MET value and body parameters, give me a wildly different result. The differences aren't subtle, so that's what has me wondering where the Fitday formula got it's origins.

As an example, a stationary bike at the gym tells me I burned about 300 calorie in 30 minutes. Using the same numbers here on gives me a number about 50% higher.

cjohnson728 08-22-2012 07:14 PM

Hi j., as far as I know, it's not a deep dark secret, but I did forward this to moderators and other support. The quick answer is that the formula that is used here is similar to the ones widely used by others, but to get a definitive answer will take some digging. Given that the techs are pretty busy programming new and awesome stuff into the site, it may take a bit.

I agree that the numbers should not be 50% higher, but also keep in mind that the counters on the machines at the gym are widely thought to be rather inaccurate. Sometimes I've had the thought that it would be cool to just have a device we could plug ourselves into and it would automatically calculate calories eaten and burned! Using a heart rate monitor was as close as I got.

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