Do weighing scales that measure body fat % actually work?

There's a weighing machine at our local super market and you put your hands on 2 handles at the side and it also measures your body fat %. I've used it twice and both times it's shown 21.5% - do you think this is precise or should I take it with a pinch of salt?

Public Comments

1. I don't think a machine in a grocery store will be very accurate at all. These machines can be fairly accurate but I would try a gym or dietician to figure this out.
2. It depends on the type you buy. Usually the cheap ones won't work. The quality won't be good.
3. thats not accurate at all, get a physio to do it and then you know the figure for certain
4. They aren't very accurate. It's impedance balance testing and a number of factors can throw off percentages including hydration levels. If you weigh first thing in the morning, your percent will be lower. Ditto on after exercise (lose moisture in sweat). But drink a large glass of water and wait 10 minutes, then your fat percent increases. Best way to tell? Take off your shirt and look in the mirror.
5. I think they are less accurate, the more muscle you have. My brother and husband used my body fat scales and their body fat came out as 18% and 24% respectively. I know my brother doesn't have an ounce of fat on him and my husband is a competitive body builder lol, so you tell me. HTH : )