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About body composition

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How does body composition measurement work?

The body composition feature works by sending a small and harmless electrical current through your body. The current flows more easily through muscle than through fat, so by measuring how much current flows at various frequencies, an estimate of the percentage of body fat and muscle can be calculated. Everything else that your body is composed of falls into the “other” category.

Why measure body composition?

Measuring what your body is made up of gives you more relevant results than simply weighing or calculating your BMI (body mass index). Since muscle weighs more than fat, you could gain weight from strength training, yet look slimmer. By measuring your body composition over time, you’ll be able to see if your muscle and fat percentages go up or down and you’ll have a more accurate picture of how your body is changing.

Accuracy of measurements

When looking at body composition measurements, the important thing to note is the trend over time. Many factors, such as exercise, eating and hydration levels can influence a single measurement and therefore cause minor daily fluctuations. You’ll be able to see how your fat and muscle percentages change over time in the TomTom Sports app and on the TomTom Sports website.
We recommend that you measure your body composition at the same time of day, and follow the steps for How to accurately measure body composition.

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