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Hacking Your Watch for Weight Loss, Part 2

Use your smartwatch to help you change habits instead of paying too much attention to the active calories.

As you can see, smart watches have varying forms of accuracy when measuring heart rate:

The Apple Watch achieved the lowest error when measuring heart rate: 2.0% (1.2%-2.8%).

Samsung Gear S2 had the highest error: 6.8% (4.6%-9.0%)

The Fitbit Surge performed best with the lowest error of all seven trackers: 27.4% (24.0%-30.8%).

PulseOn had the highest error: 92.6% (87.5%-97.7%).

To rack up fake steps you can sit on a couch and shake your wrist; toss your fitness tracker in the dryer, or attach your tracker to an electric saw blade, power drill, paint can shaker, ceiling fan, metronome, dog, bike wheel, or hamster wheel.

Most popular activity trackers and smart watches (such as products from Apple, Amazfit, Coros, Fitbit, Garmin, Honor, Huawei, Polar, Samsung, Suunto, Withings, and Xiaomi) use an accelerometer to sense movement. This detects acceleration, which is your change in speed relative to time.

Devices typically measure acceleration in 3 planes; they are known as triaxial or 3D. The planes are X, Y, and Z, which are accelerations from front to back, side to side, and up and down. (To view great examples of raw accelerometer data for several activities, visit Unfit Bits: Research.)

If you wear a fitness tracker on your wrist and you move your arms around (even if you aren’t taking any steps) the sensor detects accelerations, which may be counted as steps. Hence fitness trackers can show, steps for napkin folding (identifed by a waitress), drum playing, and more.

Conversely, if the sensor can’t detect your changes in speed, it may not count steps. Thus a wrist-based tracker may not measure activity done while your arms are motionless (cycling, carrying groceries, or pushing a stroller or lawnmower).

However, if you’re moving over an uneven surface, the sensor may pick up wrist vibrations, giving you step counts that may or may not correspond with your actual steps. This is a key reason that a tracker’s location on your body is very important.

Your calorie burn during activity can be off anywhere between 40% to 80% of your actual energy expenditure, and that wearables can overestimate calorie burn by 14 to 23 percent.

Remember that while calories in vs. calories out is important for measuring energy, so is the quality of fuel being provided to the body.

Carbs are the quick energy, fast producing fuel that can foul up the burn of stored fat (energy). Try to eat healthy fats, protein, or low net carb fruits and veggies before or after your workout if on a weight loss journey.

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