I'm not saying that there is zero truth to the output that the machines give you but I do now that the use of such a machine is normally relegated to a method of selling memberships to potential new clients. As far as I know doctors do not use this machine and it is merely something for people to spend to much money on for their own home or to have some sort of really advanced looking tech at the entrance to a gym.
They look like this and they are in my opinion, completely ridiculous. According to the person that administers the test on you, this scale that you also grab with your hands is meant to send some sort of electronic but not painful waves or signals from your hands all the way to your feet and then it can magically tell you how much body fat you have in each major part of your body.
Is it true? I would imagine not because to me it seems like a bunch of hokum.
I was recently checking out a new gym with a rather overweight friend of mine and before they would even let you look at the gym - which is what we were truly there for - they had us go through the process of standing on this thing and then waiting for it to "beep bop boop" its way into making a printout that told us exactly where our problematic areas of fat were on our body.
The results were not just impossible using a machine in my mind, but also quite obvious. For men your body fat is likely going to be concentrated around your belly, and for women it is going to be in the butt and thighs. We don't need a computer gizmo to tell us that. It actually wouldn't surprise me if one of the other gym employees was behind the counter where the machine is inputting random numbers into your printout based solely upon what it is that you look like and then just putting your actual weight on there as well.
This system is also something that I do not think is a very good selling point for the gym either. Especially for my friend who is probably around 50 - 70 lbs overweight, customers tend to not enjoy being told how fat they are by someone who works out for a living. Even with me, someone who is in relatively good shape, the ultra-ripped trainer felt compelled to advise me on my diet even though I wasn't asking for that information nor was I even a member yet. For my friend, it was much more humiliating and this condescending attitude on the part of the trainers was enough to convince us that we definitely were NOT going to sign up for a membership there.
These budget machines that they use at gyms should not be taken seriously and doctors do not ever use them either that I am aware of. This could be because they can't charge hundreds of dollars per use as is typical with anything medically related though.
pro athletes and other such really wealthy people use a machine called a DEX or DEXA and no, I do not know what that stands for but I presume it is an acronym. This machine will break down your body's entire composition of everything and having access to this incredibly accurate readout will cost you upwards of $1000 per go.
I think a better way to approach measuring your BMI or how much fat you have in your body would be to just look in the mirror. It's free and having that information isn't going to really benefit you anyway. If you are overweight, you probably already know it and don't need to get scientists involved in order to figure it out.