How accurate are body fat analysers? Also a bargain!

[Ciber]

I've been working on my shape and as a way of measuring progress I've used the machine at boots and the one in my local tescos health section as well. The two machines roughly agree, giving me a loss of body fat over 6 moths which agrees with what I see in the mirror. Today I saw a hand-held body fat analyser at maplins, so I thought that would save me money on using the machine in tesco (70p a go). http://www.maplin.co.uk/module.aspx?moduleno=31714 (£6.00) The trouble is the one I bought in maplins says I'm much fatter. Later on after looking up body fat analysers to find more info I saw one on offer on Argos for 99p so I went and got one of those too. http://www.argos.co.uk/static/Produc...3EBODY+FAT.htm A right bargain by the way, for £1 you can't go wrong really! That one tends to agree with the maplins one and seems to work much the same. I think I'll try to get a refund on the maplins one tomorrow or ebay it.

The thing is I don't think the hand held device is right. Surely the big machine at boots or tesco is more likely to be close to the truth. I definitely haven't doubled my body fat since measuring at tesco, in fact I'm sure it has gotten lower if anything. Anyway, here are the measurements:

25th Jan 08 at Boots machine: 84.2kg, 17.9% body fat

19th July 08 at Tesco machine: 81.1kg, 13.2% body fat

I weighed myself 17th sept 08 at the gym, 81kg.
4th Oct 08 using Maplins device: 23.5% body fat. - no way! I'm thinking no way is that right.
using Visiq device from Argos: 24.8% body fat. Hmm even worse!

Now I know these things are only supposed to be an estimation, but I'm confused by this much disagreement. Very much bemused!

[TooNice]

That's why I use those devices to work out an estimate of changes over a period of time. If they are worth anything at all, they should at least be somehow consistent if you gain/lose body fat, assuming you try to keep other variables as constant as possible (i.e. if you have a habit of weighting first thing in the morning, keep doing that), and don't try to 'cheat' the device (wet hands/feet/body). My Tanita scale seems to work well enough for that purpose. If I spend two months eating oven pizzas and not doing exercise, I will see my body fat go up a bit and if I go to the gym every other day for 2 months, I will see it go down over time (though to be honest, my weight/body fat doesn't fluctuate much in the first place). I also try to compare it with other means of body fat measurement. For most part, my body fat % is reasonably consistent across the different measurements I've taken, though I've not tried those hand-held devices.

Keep in mind that most of those devices probably don't measure the body fat through your entire body, and make approximation based on the area it measures. It may well be that you have more fat in those areas than others, but less in other places. The machine wouldn't know that.

[Ciber]

Would this be any good then? http://cpc.farnell.com/LH00884/test-...questid=188866