How are some electronic scales able to measure body fat or bone density?

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How are some electronic scales able to measure body fat or bone density?

In: Technology

Body fat scales use a technology called bioelectrical impedance analysis to measure body fat.

A small, unnoticeable electrical current is sent from one foot, up one leg and down the other leg. Fat is a poor conductor of electricity compared to other components of the body such as muscle. The more resistance the electrical current experiences, the higher the fat.

They are not particularly accurate, I believe.

They do a simple BMI calculation based on height and weight and display it. The real answer is they don’t measure, they approximate.

I don’t know about scales that can measure bone density, but I can explain how bone density is measured using medical DEXA machines if anyone is curious!

Traditional Xray machines use very high voltage to produce tons of high energy photons to pass through your body, and because different tissues in the body have different density, they block a certain amount of photons, creating the different levels of grey to differentiate bone, muscle, fat, air, etc. Bone density can be described in general terms on some exams because very dense bone and osteoporotic bone block/attenuate xrays differently and in different areas of the bones. DEXA machines use dual energy (very high and low X-ray voltage) and much fewer photons to produce an image which is not as detailed, but focuses on contrast and uses precisely calibrated software to provide measurements of bone density. Typically the lumbar spine, hip, or radius is used.