I have some physical understanding, but how can they tell my body fat % and how accurate os that?
In: Technology
It uses something called bioelectric impedance. Fat and muscle conduct electricity differently because muscle has more water content while fat is an insulator (slows down electricity). The little silver parts you stand on send out a super small electric signal that you can’t feel but it measures how quickly it goes out one silver piece and back into the other. Since it knows how fast it goes through water/muscle and fat, it can estimate how much of each it went through. It also uses characteristics such as age to help it be more accurate. BIA is accurate to within roughly 3-5% under perfect conditions, but how hydrated you are, your body temp, etc can alter results quite substantially.
They have metal pads that you stand on while bare-foot. It puts some small amount of electricity through your body, measures how much goes through (the “resistance” of your body), and estimates your body fat percentage based on the results.
It’s reasonable accurate as long as your body fat is, uhh, normal. If your body fat is in unusual places – perhaps as a result of medication or surgery – then the estimate may be off. As with all things electrical I suggest making sure your body is completely dry. But if you’re using it daily or weekly to measure your weight loss/gains, the general trend of going up or down will be fine.
Imagine you’re standing on the scales with bare feet. The scales send tiny bits of electricity into one foot, which travels up one leg, down the other, and out the other foot and back into the scales.
Electricity travels through fat and muscle (and even water) slightly differently, so depending on what the scale gets back through the second foot it can work out what you are made of.
They don’t measure your fat and muscle in your upper body, so the result is mostly just your legs.
They aren’t very accurate, because as mentioned earlier electricity also travels through the water, which will mess up the results the scale gives you.
They can be used to measure fat gain/loss over time, however, as long as you’re never really thirsty.
I had developed computer software for Tanita scales. They work by giving different doses of electricity through metal pads and reading the impedance values. Many models include hand parts so upper part is also measured. Then they correlate that data to their internal data set and produce the result. The only accurate way to read how much fat you have is to remove all the fat from your body anfter you die and then weight it. Close enough version includes submerging in special water pods.
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