I have electronic scales, which allow you to enter your age and sex. When I step on my scales as a 33 year old man, I weigh 72.5 kg. Anonymously, however, I only weigh 70.7 kg.
My curiosity was piqued, of course, and I did two more experiments by placing a towel over the scales (the scales measure my body fat with a small electric current – the towel blocks the current). No difference as anonymous person, but as a 33 year old man without body fat measuring I weigh 70.7 kg.
So based on the measurement of my body fat and my age and gender, my scales add another 1.8 kg to my weight. I have no idea why.
