Why calories tracking is not so easy? What’s wrong with smart watch calorie tracker?


Having dealt with the myths about fat burning, let’s move on to the related issue. It’s about pure carbs and calories tracking. Their consumption, counting and burning.

The definition of net carbs was initially popularized by websites such as MyFitnessPal or FitBit. Their service with the appropriate account settings allow to subtracts calories burned during training from the calories consumed during the day.

As a result, the calories tracking shows the user can consume during the day more calories:

smart watches calories tracking - calories balance - calories in and calories out

Example: the user calculated daily calorie intake, and it is 1703 kcal per day. At the moment he ate 467 kcal.

However, during training, according to his SmartWatch, he burned 302 calories. The service takes into account these calories as an increase in metabolism, that is, the user today needs more calories because of training. Therefore, subtracts them from eaten. It turns out that the user ate not 367, but 165 calories. Are these calculations correct?

Mathematically all is true, after all, there is a theory about CICO (Calories In, Calories Out), according to which only the balance of energy (calories) matters for fat burning. So what’s the problem with smart watches calories tracking?

SmartWatch is the devil

In 2014, 5 million smart watches were sold worldwide. In 2018, the number of devices sold in this category exceeded 140 million. In applications such as the Fitbit or MyFitnessPall, the number of users in the millions. All this means that the number of people who use devices for daily calories tracking is growing rapidly. At the same time, the accuracy of the data is not controlled, it works on the basis of assumptions.

If you are refueling at a gas station, you know that the counters have the correct number because this device is checked regularly. In case of smart watches there is no such control – the manufacturer can program the device according to any algorithm of its choice, no one checks it.

The phenomenon itself is not new, because gym cardio equipment, such as treadmills or elliptical cross-trainers, for years tickle the ego of fitness club guest, delighting them with calories tracking information that display hundreds of burned calories. But this phenomenon has become so widespread only recently. To make matters worse, some people count literally every burned calorie.

calories tracking in the gym

The attitude of modern society to calorie tracking can be compared to playing in a casino. Where calories are casino chips that we can change for food.

How exactly do smart watches count burned calories

The app will tell you how many calories you burn when walking, sitting, sleeping, vacuuming or shopping.

You sit all night and watch TV? It seems nothing, and then it turns out that you’ve spend about 150 kcal, which is just equal to the caloric content of a small beer can. You were shopping, and you burned 200 kcal walking around the store? You can eat an extra bar of chocolate, the calories balance will be zero, right? Or not?

In the 2016 study the reliability of calories data provided by the popular smartwatch (Fitbit, Jawbone UP24) was estimated. It was found that the number of calories, indicated by these devices as burned, overstated by an average of 16-40%.

In 2017, re-examination was carried out. This time the device that analyzes the heart rate and transforming the measurements in the calories burned (including the Fitbit Surge and Apple Watch) were tested. The results showed that although the tested gadgets measured heart rate quite accurately, the calculation of burned calories was still not accurate. The inaccuracy was 27%. And in extreme cases, smartwatches even showed data 93% higher than the actual energy consumption!

smart watches calories tracking fail

How significant is the error of a smart watch in calories counting

Let’s assume that the lowest error is found, i.e. 27%. How critical is this? Let’s do the math.

Suppose you train 3 times a week. And your smart watch shows that you burn about 600 kcal per workout. However, they are wrong by 27%, i.e. 162 kcal, which means almost 26 thousand cal per year.

This in turn means that by consuming these calories, you not only lose weight, but even get fat by about 4 kg this year. And in this example we are only talking about 3 workouts per week and we assume the lowest of the found errors!

Does this mean that smart watches are useless in calories tracking?

No, absolutely not. They are useful and worth using. But calorie data isn’t an excuse for us to eat more calories.

Smart watches are extremely useful thing in many other matters. Including in terms of weight loss and health.

It is worth following the smartwatch instructions to keep track your daily activities. For example, to pass a sufficient number of steps per day. The smartwatch does a good job of reminding you to move more.

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