Guide
How accurate are body fat scales designed for home use?
by Oliver Fischer
Review: the Tanita RD-545 body composition scale
13.6.2019
Translation: Katherine Martin
These days, bathroom scales can measure anything from muscle mass, to hidden fat, to metabolic age. And sure, your weight too.
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
How does BIA work?
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
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?
Patrick Bardelli
Senior Editor
Patrick.Bardelli@digitecgalaxus.chFrom radio journalist to product tester and storyteller, jogger to gravel bike novice and fitness enthusiast with barbells and dumbbells. I'm excited to see where the journey'll take me next.
