How Accurate are Body Composition Watches?

Body composition watches hit the market, but are they accurete?  

Our watches don’t just tell us the time anymore. They send texts, answer phone calls, measure your heart rate, track your steps and even monitor your sleep! And now watches claim to measure your percent fat.  

So, are they accurate? Hmmmmm, here’s some recent study data...
In two studies comparing smartwatches to Dual-energy X-ray Absorptiometry (DEXA) (Bennet, 2022) and to an alternate 4-Component Model (Brandner, 2023), the watches underestimated percent fat by 2-4%. The watches also overestimated fatness in those with low body fat and underestimated fatness in those with higher body fat.  

The bottom line is that Body Composition watches have an error rate for estimating percent fat that is plus or minus nearly 5%, which puts this method only as good as BMI (for estimating percent fat). In other words, if your watch says your percent fat is 25%, your actual percent fat is really somewhere between 20% and 30% which isn’t very helpful for most of us. And if you measure under conditions that are not ideal, that error rate increases.  

So, it may be better to spend your money on some healthy snacks or a gym membership!