Is your fitness tracker making you gain weight? How accurate are they really and which one is the best?

Isn't it a great feeling when you check how many calories you burned at the end of your workout and it says "500 calories"?

Wearable gadgets have flown into our lives and they're hyped more and more. But are they actually accurate?

Not really. That hour you spent on the treadmill might not have burned as many calories as the tracker wants you to believe. And here's why.

How do fitness tracker calculate calories burned?


The calorie counter in a fitness tracker is based on your basal metabolic rate (BMR), recorded activities by the tracker itself or activities you log manually, and sometimes your heart rate.

Here's the problem: Trackers only keep an eye on some metrics. Many of these can be skewed by all kinds of circumstances, such as emotional stress, hydration levels and current training status, which can lead to misleading results.

Plus, they don't have all the numbers they need, to accurately determine your caloric needs. Your weight and age alone are not even remotely enough, to get a decent result. It's clear that a 90kg/200lbs person with very little fat burns a hell of a lot more than a person with the same weight, but mostly fat.

Trackers don't account for that, nor for even harder to determine factors like your individual metabolism, hormonal state, etc.

What about gym equipment. How do they get the number?


It's the same as with fitness tracker. The calorie counters are based on estimations and averages.

Here's how they get these estimations:

A lot of people had to run on a treadmill hooked to a mask, which calculates the amount of oxygen they needed. With that amount, they calculate the calories burnt. The average is then used for the gym equipment, which spits out a number based on the weight you entered and how fast the drums were turning.

This number can be somewhat accurate if you're close to the average, but chances are it's highly inaccurate if you're a frequent gym visitor.

Why you might gain weight with a fitness tracker

I see a lot of people using wristbands and calorie trackers, but the weight just doesn't want to come off or they even gain weight. The problem is that they overestimate the calories they burn.

If you only rely on the tracker and adapt your caloric intake to what it tells you, you might not even be in a caloric deficit anymore, but in a surplus.

So many people are fixed on this number, that they forget to see the bigger picture. Obesity can be the result of a number of factors, like medications, health conditions, genetics, portion control problems, wrong diet, binge eating and so on. Just giving someone who needs to lose weight a fitness tracker doesn't treat the problem. Always treat the cause, not the symptom! Maybe they need a stronger intervention than simply a device (that only presents them with misleading data).

A motivation booster but not a tool for weight loss

See, the main problem is when people make crucial decisions based on the tracker. If they go to the gym and think they've burned 400 calories, then they might feel they've got 400 extra calories to play with, when in reality they only burned 200 calories.

Oh and by the way: if it says you've burned, say 500 calories, in 1h of running on the treadmill - even if that number were correct (most likely not!), that's not on top of your calories, but in place of them. An average male will burn 60 calories per hour while at rest. Which means an extra 440, compared to sleeping! Or maybe an extra 200-300 compared to working/walking/shopping/whatever. But certainly not an extra 500!

However, fitness trackers have been proven to help users to stay motivated with their fitness goals by encouraging regular exercise.

You really want a fitness tracker? Then which one is the best?


Personally, I wouldn't recommend to buy a fitness tracker. However, some of my clients started to rather walk or bike somewhere instead of taking the bus, since they wear a fitness tracker. So if you want to and have the money for this optional item, go ahead.

Here are a few tips to help you choose the most accurate device:

  • Pick one that monitors your heart rate automatically and continuously right on your wrist. Those track calories more accurately. Plus, heart rate data is surprisingly good. Don't buy one without HR sensors
  • You also want a device that allows you to enter as much data about yourself as possible. From height, weight, age and sex, to body fat
  • Runners should look for devices that measure stride rates and cadences
  • Cyclist should focus more on power meters

So, if you really feel the urge to buy one, my tip would be either the Fitbit Charge HR or a simple pedometer. Several smartphones have one integrated nowadays, so just use that one if possible.

We all agree that activity is better than no activity. If you feel more motivated by wearing a tracker, so be it. But don't base too much of your diet on it's results.

Do you use a fitness tracker? If so, which one and why?
