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WTF???

Or more accurately, your “fitness tracker”? They’re all the rage, and come in so many brands, shapes, sizes, colours…you name it, they sell it! The purpose of them is to track your heart and activity rate, and give you feedback on how active you are, and ultimately give you the answer to the million dollar question…. how many calories you burn.

Sounds amazing right? Strap it on your wrist, hit the gym, and hey presto, you can calculate calories in versus calories out, down to the number of steps you take. For such a small device to give so much information is pretty darn incredible, but just how accurate is it?

A recent study by fancy pants Stamford University found that fitness trackers are amazingly accurate at calculating your heart rate, with as little error as just 2% (Apple Watch). Even the largest heart rate error margin was just 6%, which considering the device goes nowhere near your heart, it’s pretty accurate!

But when it comes to calorie counting, that’s where the margin of error gets a little scary. How accurate would you say a fitness tracker is at counting calories? Maybe 5% error? 10%?

No.

The smallest margin of error for counting calories, was 27%. YES, THE SMALLEST! (On FitBit Surge). You did not read that wrong. So if a fitness tracker says you have burned 2,000 calories that day, it could actually be as little as 1400 calories. The largest margin of error was 92% with the PulseOn. Again if it stated you’d burned 2,300 calories in a day, it could be as low as approximately 1,240 calories (read the full study here: http://www.mdpi.com/2075-4426/7/2/3 ).

Why is this important? We know that calories consumed versus calories burned are directly related to weight loss. If people eat more calories than the body burns, it results in weight gain. If people are in a moderate calorie deficit (are safely consuming less calories than their body needs), it will result in weight loss. The problem arises when the estimation of how many calories a body burns in a day is inaccurate. An overestimation will result in no weight loss at best, and weight gain in the worst case scenario. Conversely is the estimation is too low, it can result in drastic unsafe weight loss and possibly irreversible hormonal changes (like the 1200 calorie a day diet…don’t get me started on that crap!). The most accurate way to measure calories burned in a day is via an oxygen consumption machine to determine how much oxygen our body needs and calculate our calorie burn from that. Which is really easy because everyone has one of those, right?? OK so not everyone has these, so the next best thing is to calculate your Basal Metabolic Rate. This is the number of calories your body burns at rest. The next step is to multiply this number by the amount of activity you do on a daily basis. You can use this handy link to work it out:

https://www.muscleandstrength.com/tools/bmr-calculator

Nothing is 100% accurate, but this calculation is the quickest and most accurate way we can work out how many calories your body needs, which is so important for weight loss. Often when I introduce people to this calculation, I will hear protests of, “but my FitBit says…..”, or, “I treated myself to a take away because my iWatch said I burned xxxx calories on my walk today”. It’s an easy trap to fall into, so make sure you do the calculation yourself so you know for sure.

Despite what you may think, I don’t hate fitness trackers. I even have one myself…..

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See?

But hang on I hear you say! You’ve just told me my fitness tracker is LYING, so why would you have one?? I guess it depends what you have one for. I use the heart rate monitor to track the peak heart rate zones I’m training in, so I can tailor the intensity of my workouts depending on what part of my Roller Derby season I’m in. But this function is useful for everyone, and with a maximum of 6% inaccuracy, it’s a good guideline of how hard you’re working in the gym. So if you feel like you’re smashing it, but your heart rate is still at 85, you know to crank it up a notch….. 😉

As always, if you’d like any help or advice on how to improve your training or give your nutrition a kick start, drop me an email at alexvalentinept@mail.com , or text me on 07875465275.