Body Fat Measurement Device Question

Yesterday, my office held a health fair. I went to get my body fat percentage measured. The technician asks me for my age (32), my height (5’10") and my weight (152). Then I grasp 2 handles on a device which spits out my body fat percentage (12%). A couple of people comment on how good that is, and I must admit that I’m feeling pretty proud.

Then I think to myself: “How did that device read all the fat throughout my body simply by me grasping the handles?” Was I duped? Did the age, height and weight answers imply my body fat %-age? Or did grasping the handles really do something magical? And how?

This was covered here:

Electrical impedence through water and fat.

Your age, height and weight and level of exercise/activity (are you an ‘athlete’?) all help the machine make sense out of the electrical impedence number that comes out.

My experience with those machines is: they suck.

If the machine is set wrong, someone with 20% body fat could be anywhere from 10-25% at the read out.