Review: the Tanita RD-545 body composition scale

Want to know something really exasperating? I have bad genes. When it comes to my belly fat, that is. I’ve suspected it for a while, but now I have it in black and white. My waist-to-hip ratio is above the norm – and visceral fat is the culprit. That’s the fat stored in the free abdominal cavity, coating the internal organs, in particular those involved in the digestive system. Drat.

I inherited that from my father along with a bald head. He was slim all his life, never struggled with his weight, but always had a slight paunch. Thanks, Dad. No matter what I do to fight it, my genes come up trumps.

Body composition scales are all the rage

I’ve had a Runtastic Libra in my bathroom for a few years now. These body composition scales measure:

• body fat
• muscle mass
• bone mass
• body tissue
• total body water

However, the data that these kinds of scales reveal by way of bioelectrical impedance analysis is often miles off the actual figures. Swiss consumer issues programme «Kassensturz» (link in German) criticised them for as much back in 2016. Now, I’m testing a product promising nothing less than the accuracy of professional medical scales.

Bathroom scales

Tanita RD-545 body composition monitor

200 kg

48

Bathroom scales

Tanita RD-545 body composition monitor

200 kg

48

Frankly, I’m sceptical. The gismo costs just under 500 francs. Professional medical scales, on the other hand, easily run into five figures, so they should be much more accurate. But is that really true? On a quest to find out, I head to SportClinic Zurich (link in German) to be weighed by qualified sports scientist Matthias Ludwig. To do this, he uses the InBody 720, which fetches a price of around 10,000 francs. I’m then able to use the data it gives me as a reference to compare with the Tanita. But first things first, time for a little theory.

How does BIA work?

This method of measurement works by sending a weak electrical current through the body. In doing so, the composition of the body, such as its proportion of muscle, fat and water, is determined. Bioelectrical Impedance Analysis (BIA) makes use of physiological characteristics, namely the varying electrical conductivity of the body’s own tissues and water. It’s this conductivity of body fluids, as well as non-conductivity or high resistance (impedance) to electric current, that form the basis of BIA measurement.

The current flows through the water in your body, which has an electrical resistance. Water’s resistance is referred to as resistivity. The membranes of the water-filled cells in the body’s water give off resistance to the current, which is known as capacitance. BIA measures the impedance of the human body. This is calculated from the vector sum of the resistivity and capacitance.

Impedance makes it possible to calculate the electrolyte volume of a cylinder filled with water. To do so, you just need to know the impedance and height of the cylinder. If you were to picture the human body as a cylinder, a person’s water volume can be calculated using their impedance measurement and height.

Setting the stage

To make sure the figures are comparable and as accurate as possible, both tests are conducted as follows:

• in the morning
• on an empty stomach
• in underwear
• after going to the toilet in the morning
• having had a light meal the evening before
• using InBody 720 at SportClinic
• using Tanita RD-545 at home

The app

The Tanita is incredibly easy to use. You just download the My Tanita – Healthcare App (iOS and Android) and set up a profile. After that, you select RD-545, connect via Bluetooth and get started.

A comparison of the results

I take this opportunity to collect and compare data from the Runtactic Libra, too:

The verdict

Just like on professional scales, Tanita sends an electrical current through your feet and hands. This is supposed to give more accurate readings than if the current were only to pass through the feet from below. The most serious deviation is in relation to body fat. While the Tanita RD-545 gives a reading of 21.6 per cent, the InBody 720 says it’s 17.8 per cent. The figures for weight, BMI and calorie consumption are very similar, but when it comes to body water, trunk muscle mass and arm muscle mass, the differences are more significant. As for the legs, the Tanita and InBody come up with virtually identical measurements. According to the InBody, my visceral fat measurement is slightly high, whereas the Tanita places me within normal range.

Tanita promises the accuracy of professional medical scales. This pledge, however, is only partially upheld. The issue of body fat percentage is especially unfortunate. I mean, it certainly makes a difference whether my body is composed of 14.3 kg (InBody) or 17.2 kg (Tanita) of fat. I’m probably not the only one to be slightly put off by a false reading, thus starting the day in a suitably good or bad mood.

What I do think is great about the Tanita RD-545 is the segmental division of the body into arms, legs and trunk. It’s especially interesting in relation to muscle quality – my favourite of the scale’s features. Instead of measuring muscle mass alone, the scale measures muscle quality too. It distinguishes between contractile muscle tissue, connective tissue and fat within the muscular structure. Nice one.

What now?

All this begs the question of whether I’m willing to spend almost 500 francs on the scale, and what to do with its data. Let’s put the question of these scales’ accuracy to one side. After all, even if all the measurements were wrong, I’d be able to see the development of individual muscle segments in any case. Provided the measurements were recorded equally wrongly each time, that is. Obviously, though, the Tanita Rd-545 can’t compete with professional medical scales. But the latter also cost about 20 times as much. So, to round things off, I’ll bring the comparison with the Runtastic Libra (which costs about 100 euros depending on the seller) back into the mix. In this case, the Tanita is a touch better i.e. more detailed. If I’m laying out every last gramme of fat onto the scales, I’m happy to dig a little deeper into my pockets. At the end of the day, I am a body analysis and performance diagnostics buff.