The company announced yesterday that Samsung's new Galaxy Watch 4 features a function that calculates body fat percentage and muscle strength. This is the latest tech company to announce a body composition feature. It joins Amazon who has a Halo Band that can calculate body fat percentage.Although body fat is a better indicator of health than weight, it is often calculated using the crude and inaccurate BMI (body mass index). Wearables could be a better way to monitor your health, Diana Thomas, a West Point mathematician who studies the regulation of body weight, said to The Verge in June.Galaxy uses a technique called bioelectrical Impedance analysis (BIA) to measure body composition. This weak current is sent through the body by the Galaxy. The signal travels faster through tissue with higher water content to calculate the body's water content. The technique estimates how much fat is in a person's body because fat has a higher water percentage than muscle.BIA can provide an estimate of body weight, but there are limitationsThomas sent an email to The Verge stating that BIA can provide an estimate of body weight, but with limitations. She explained that there is no perfect ratio between body fat and water, and that the body's water content changes over time. This can fluctuate depending on how much water someone drinks or how active they are. A study showed that BIA underestimated body fat when the measurement was taken after drinking around two cups of fluid.Most devices that use BIA for body composition tracking send the current through your feet or palms. The sensors were resized by Samsung to fit on the watch's back. In January 2021, the Healthcare Sensor Lab published a study that described the technology. The study included 203 individuals who had their body composition analyzed using the watch, two other BIA devices and a device that uses dual energy X-ray absorptiometry, an X-ray technique that shows fat distribution throughout the body. This is the gold standard in body composition measurement.Analysis showed that the smartwatch was more accurate than the DXA measurement. The calculations came out slightly closer to the DXA measurement that one of the other BIA devices. Thomas stated that the watch works as well as a smart-scale based on this study. Based on the available information, the potential error rate calculated in the study was too high for her to use it in research studies. It may be acceptable for personal use, she stated in an email to The Verge.Samsung's approach is very different from Amazons Halo's body composition analysis feature. The first is that the Halo calculates body fat and not muscle. The app allows users to take pictures of their bodies, which are then combined into a 3D image that is used to calculate bodyfat percentage. According to an Amazon-funded study, the system can also calculate body fat accurately compared with DXA.Both apps seem to be better at calculating bodyfat percentage than BMI. Although it is often used to guide medical decisions, BMI can be misleading. This can lead to misdiagnosis and perpetuate the weight-based stigma in healthcare. However, it is easy and cheap to use. The majority of people don't have the ability to access more precise, expensive machines.To find out how reliable these wearables are in real-world settings, it will take some more research. They are easy to use and fairly inexpensive. They could be used to make health metrics more easily accessible if they are able to detect trends in body composition.
