The Samsung Galaxy Watch 4 Might Measure Body Composition

The Samsung Galaxy Watch 4 Might Measure Body Composition
Photo: Victoria Song/Gizmodo

The rumour mill surrounding Samsung’s next-gen smartwatches has been absolutely buzzing these past few weeks. The latest contends that Samsung’s next flagship — the Galaxy Watch 4 — might add a bioimpedance analysis (BIA) sensor. If you’ve never heard of BIA before, it’s the same tech used in smart scales to determine your body composition.

The rumour comes via Android Authority and Max Weinbach, a tech writer with a decent track record of sussing out what’s coming next for Samsung gadgets. That said, there’s not much else to go on. Weinbach kept things snappy in his tweet, merely stating “Galaxy Watch4. BIA sensor.” Rumours and leaks should always be taken with a heavy grain of salt, but there are two main reasons to think this one might not be totally bunk.

The gist is BIA works by sending a weak electric current through your body. Depending on the impedance or “resistance” that signal encounters, you can estimate body composition as different types of tissues have higher or lower electrical resistance. Fat is more resistant to electricity compared to water, blood, and muscle. Most smart scales using BIA, for instance, claim to measure body fat, muscle mass, water, and occasionally, bone density. To do this, you need a pair of electrodes — one to send out the current, and another to receive it, thereby creating a complete circuit.

That should sound familiar, as it’s also how advanced smartwatches — like the Samsung Galaxy Watch 3 — take ECG readings. For ECGs, the reason you’re asked to place a finger in a specific area on the watch is to complete a circuit. Samsung already knows how to send and read electrical currents sent through the body, so it’s not like it’d be an extremely heavy lift to add body composition analysis.

The second reason is Amazon’s also dipping into body composition with its Halo tracker and app — albeit using a totally different method. Amazon Halo measures body fat in an extremely problematic way. It requires you to strip to your skivvies and take pictures on your phone to get an estimate of your body fat percentage. You’re also shown a 3D model of your body that comes with a slider, so you can see how you’d look with minimal body fat and a six-pack, or a high percentage of body fat. The company claims its method is highly accurate and comparable to clinical lab tests, though accuracy isn’t the problem with Halo.

So given that another major tech company is dabbling with body composition, and the fact it wouldn’t be a huge technological lift, it’s reasonable to think Samsung might introduce this kind of feature. Among flagship smartwatches, we’re also in the midst of a “health tech arms race.” So far, Apple, Samsung, and Fitbit have led the pack. Apple and Samsung are both heavily rumoured to be working on blood glucose monitoring and Fitbit introduced an electrodermal activity sensor with its ambitious Sense smartwatch. However, BIA is something neither Apple nor Fitbit has brought to the wrist. (Fitbit does, however, have a smart scale that uses this tech.)

The thing is, while this could give Samsung a leg up, it’s also wading into murky territory. Measuring body composition is, on its own, not a bad thing. Metrics don’t have any morality. However, BIA is not the most accurate measure of body composition, although it is the most easily accessible to consumers. For example, if you drink a lot of water, or are dehydrated, that could throw off your BIA measurements. Clinical methods, like DEXA, air displacement plethysmography, and MRIs, are more accurate but are expensive and require you to go to a lab. In short, BIA is fine for roughly estimating your body composition over time — but you can get bunk individual readings.

Giving consumers an accessible way to gain insight into their training or weight loss efforts is, broadly speaking, a good thing. However, there’s a lot of nuance to interpreting these results in a responsible way. If done carelessly, like Amazon Halo, you’re possibly handing people with body dysmorphia or eating disorders a dangerous tool.

Samsung has made strides in recent years to improve its health offerings, largely to great success. There have been a few hiccups, but after reviewing the last four Samsung smartwatches, I can say each watch has been better than the last and Samsung itself has taken care to comply with regulatory bodies like the FDA. Personally speaking, Samsung has a better chance of pulling off body composition features than Amazon, as it has way more experience in health tech. However, it is nerve-wracking to imagine Big Tech wading into the incredibly nuanced and controversial relationship between body fat and health. If this Pandora’s box has to be opened, here’s to hoping it’s done with more care going forward.