Scale comparrison

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Ok - I have been using my Ikea scales since I started paying attentiion to my fitness back in September. they ahve done me fine and I will continue to use them. This morning I weighed myslef before breakfast and morning hydration - as I normally do. I was 68kg, which is about right.

this afternoon I go to a new gym for the first time and got a ftness assessment. They measured my height and weight - 69.5kg and 155cms. No problem. I had breakfast and water since my earlier weigh in. they put my data into the computer, which was connected to this high tech analyser :

http://www.tanita.co.uk/index.php?id=102&tx_f03showxtcommerceproducts_pi1[showUid]=1152&cHash=e2e62046bb

All my muscle/fat mass was then calculated. fine, but then I noticed they had input for my height 144cms, instead of 155cms. So I had to go on the machine again. My weight then came out at 65.5kg!!! They couldnt explain why as one was Philipion and one was Tunisian - both had limited English. All I got out of them is "Oh you are old madam" and "Oh you have a lot of muscle madam"

Are there any fitness professionals familiar with this equipment that can explain why I had lost 4 KG in the space of 4 minutes!? I am really curious!

I am not going to pay too much attention to the data generated - it was consistent with one thing though - my remaining excess body fat is around my trunk and upper legs. Technology eh - I can look in the mirror and work that out!