Fitness trackers and smartwatches have become quite the go-to devices for fitness and health tracking. One of the early movers in the wearables market was Fitbit which continues to enjoy a certain amount of fan following. Fitbit makes smartwatches as well as fitness bands that come with a plethora of features. The one feature that most people end up monitoring on a Fitbit device is the number of calories they’ve burned in a day. But how does a Fitbit calculate how many calories are burnt in a day? Read on to find out:
What is BMR and why it’s important?
Before we get into how Fitbit does the calculation, it is important to know what BMR is. BMR or basal metabolic rate is the rate at which a person burns calories at rest to maintain vital body functions (including breathing, blood circulation, and heartbeat). You can estimate your daily BMR with the commonly used Harris-Benedict equation. This is a formula that takes into account your height, weight, age, and gender to find your BMR. Here’s the formula for it:
Women:
BMR = 655 + (9.6 × weight in kg) + (1.8 × height in cm) – (4.7 × age in years)
Men:
BMR = 66 + (13.7 × weight in kg) + (5 × height in cm) – (6.8 × age in years)
How does Fitbit use BMR for calorie calculation?
What a Fitbit device does is that it combines your basal metabolic rate (BMR) and your activity data to estimate your calories burned. If your device tracks heart rate, your heart-rate data is also included, especially to estimate calories burned during exercise. The number you see on your Fitbit device is your total calories burned for the day.
Your BMR is based on the physical data you entered into your Fitbit account (height, weight, sex, and age) and accounts for at least half the calories you burn in a day. Because your body burns calories even if you’re asleep or not moving, you see calories burned on your device when you wake up and will notice this number increase throughout the day. So there will be days when you haven’t exercised anything and spent a day watching Netflix and Fitbit might show calories burnt on the higher side. That is because your body is always burning calories. And Fitbit takes that into account.