Choosing a Health and Fitness Ecosystem - Part 3 - How Calories Burned is Determined

How Calories Burned is Determined

If you have ever done a side-by-side comparison of 2 devices that can calculate your calories burned, either throughout your day or for an activity, then you noticed that they gave anywhere from slightly to dramatically different results. My favorite example is when I was comparing FitBit Charge HR, Garmin 920xt with HRM strap, and non-HR FitBit Flex. The activity was a 30 minute run on the treadmill at a 10 min pace. My burn with Garmin was about 260 calories. The FitBit Charge was just under 280. The Flex was just over 310. So if I was trying to lose weight, and I was relying just on the Flex, I would have thought I could eat over 50 more calories...which is a super yummy snack. That's not good. However, it's not totally bad either and I will explain why.

The Flaw of Caloric Burn

Despite what all of the fitness sites will tell you, heart tracking for determining calorie burn is flawed in so many ways. For example, heart rate monitors are designed to work in an optimal condition of elevated heart rate for a period of time. So, for people who do strength training, caloric burn result will typically be wrong. I am not going into the full details of this, because it's not relevant for this article, but know that your body is a complex machine and it burns calories different based on how your muscles and cardiovascular system are engaged.

I am not saying to throw out your calorie burn results; but I am saying you need to understand that results are based on usually complex equations that are still flawed, because every person's body burns calories a little bit different from the next.

HRM vs. Non-HRM

I am not trying to pick on FitBit, but they are the easiest to use for this example. We are going to use the FitBit Flex and FitBit Charge HR for this segment. Devices and formulas have advanced very far these days, so non-HRM devices that show calories have dramatically improved over time.

Quick disclaimer: I won't be posting any exact formulas because I am not well-versed in the legal jargon that the various companies have around their proprietary formulas, and since I figured out a bunch of them, I fear posting them would put me in trouble. That said, however, I will post what typically goes into the calculations.

At the very basic fitness tracker level, meaning Non-HRM, it will take into account, your age, height, weight, and steps. Most will use your gender as well. Moving up the list for Non-HRM, some have average caloric burns in addition to the various data I already mentioned. Some will even go as far as to then see your averages and adjust accordingly. However, this gets very inaccurate since it needs heart rate.

So, Heart Rate Monitors. The most basic will take into account your age, weight, and heart rate from the activity. It doesn't care about steps, gender, etc. As you can guess, the more advanced keep adding more variables to get a more accurate picture of caloric expenditure. In addition, devices that have the ability to track heart rate (HR) all day, have different formulas than that of a physical activity. So if you don't workout or overexert yourself, it will use one formula to determine your full day calorie burn. If you also exercise or do some activity that raises your heart rate to a certain level or higher, then it will use a different formula, and then add those 2 values together. The devices know to not count workout time into the overall daily burn, since you would get over-inflated results.

In addition, most of the new HRM's and their fitness device (can be separate or the same device) will watch for patterns and adjust the burns as your fitness improves. For example, if I start running for the first time, and I am a bit overweight, my heart rate is going to be higher, and I am going to see a pretty decent calorie burn from a run. Maybe a couple months later after I have lost some weight and my cardiovascular system has more endurance and is more efficient, I might only be burning a fraction of the calories for the same effort.

What Do I Choose?

Despite the above probably being confusing, the decision on whether or not to get an activity tracker or fitness device that can track heart rate is fairly simple. If you aren't someone who counts calories, doesn't care about calories, or you aren't doing any sort of activity or training that you need heart rate data, then there is no reason to get a device that tracks heart rate. Nice and simple, right?

Summary

\In conclusion, many people who just want a device to help keep them active, track activities, or to claim some work or insurance incentives, do not need a device with heart rate tracking capabilities. However, if you don't fall into those categories, you will probably want one; you might not use it right away, but you will. Up next I will be doing a long series of discussing the good, the bad, and the ugly of the various ecosystems out there.