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Old 03-31-2010, 04:57 PM
 
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Default How accurate is bioelectrical impedance analysis for measuring body fat?

As I noted a couple months ago, after losing about 40 lbs, I have gained some of that weight back -- about 10 pounds or so. However, I wasn't sure if the weight gain was due to fat or muscle, since I have been lifting weights for the past year or so.

So on Saturday, I went to a health fair where they used bioelectrical impedance analysis (BIA) to calculate body fat. Basically, I had to stand barefoot on this bathroom scale type device and it registered my body fat. It came in at a really good level -- about 10.8%. But when I got home, I read disclaimers that BIA is not always accurate, and can be thrown off by a number of factors.

So I'm wondering how much faith I should put in the device. Hopefully my measurement isn't too good to be true! Any experiences with BIA analysis?
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Old 04-01-2010, 10:28 AM
 
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Not very accurate.

Body fat percentage - Wikipedia, the free encyclopedia

There is a section on methods in that entry. Personally I was getting dehydrated a lot and was veiny even though the scale number said my body had fat to shed. I forget the exact numbers but I gained 10 pounds on purpose and feel much better. With the error factored in I was getting too close to 10-12% in the math. That is essential fat to live (for a F) so I thought it was best to gain to avoid too low body fat health issues.
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Old 04-02-2010, 07:50 AM
 
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I have one of those fat scales. I don't put a lot of faith in the percentage that it gives me every day -- I don't want to believe it! ha! -- but I DO use it as a measurement of progress. As I lose weight, that fat percentage slowly goes down, so I just embrace seeing the number go down, rather than focusing on what that number actually is.
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Old 04-02-2010, 09:02 AM
 
Location: Tucson
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There's only so much these scales can do... I have a Tanita body composition monitor. The fat percentage (just like the weight) varies throughout the day. I believe it's based on the level of hydration, which is very different at various times. The body fat percentage is supposedly the most accurate in the late afternoon, before dinner. It makes sense because the body is dehydrated right after getting up in the morning. Yes, many people question the accuracy, but it IS as accurate as it gets. As Tanita folks mention on their website, the only absolutely accurate way of measuring body fat is autopsy and you don't wanna do THAT!
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Old 04-02-2010, 09:22 AM
 
Location: SoCal - Sherman Oaks & Woodland Hills
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I thought for sure I replied to this thread yesterday. But........ oh well.

Those devices are fairly accurate with the top of the line Tanita products being a bit more accurate than others. The most accurate ways of measuring your body fat are:

1. Water displacement test.
2. Body fat calipers.

Other methods are really no more than "guesstimates".

I suggest getting some caliper and going about it the less expensive (and more accurate way) than those scales. Most caliper companies have websites where you can input your height, weight, sex, measurements of wrists, ankles, hips, waist, neck, etc. along with the results from the calipers and you will end up with pretty good body fat % estimate.

With the type that the OP mentioned (along with the Tanita Ironman) its important to measure at the same time during the day because those things are sensitive to the water levels in your body. In the morning is probably best time to use it.
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Old 04-02-2010, 09:56 AM
 
Location: Tucson
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Quote:
Originally Posted by LaoTzuMindFu View Post
In the morning is probably best time to use it.
No, it isn't. It's only the best time to feel the lightest.

Q: Are there optimal conditions for determining body fat percentage using Tanita's products?

A: Yes, there are:

Select a consistent time of day, and stick to it.
With an empty bladder
When normally hydrated
Unclean foot pads may interfere with conductivity.
Nylons interfere with conductivity. If it is absolutely necessary to measure in nylons, use a drop of isopropyl (rubbing) alcohol on the foot pads to act as a conductor.

Early morning is not recommended because the body is often dehydrated after a night's sleep. Once you have established your baseline, monitor body fat about twice a month. Checking body fat more frequently is not beneficial as changes occur slowly over time.


Tanita | FAQ
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Old 04-02-2010, 10:04 AM
 
Location: SoCal - Sherman Oaks & Woodland Hills
12,980 posts, read 17,910,902 times
Reputation: 10491
Quote:
Originally Posted by sierraAZ View Post
No, it isn't. It's only the best time to feel the lightest.

Q: Are there optimal conditions for determining body fat percentage using Tanita's products?

A: Yes, there are:

Select a consistent time of day, and stick to it.
With an empty bladder
When normally hydrated
Unclean foot pads may interfere with conductivity.
Nylons interfere with conductivity. If it is absolutely necessary to measure in nylons, use a drop of isopropyl (rubbing) alcohol on the foot pads to act as a conductor.

Early morning is not recommended because the body is often dehydrated after a night's sleep. Once you have established your baseline, monitor body fat about twice a month. Checking body fat more frequently is not beneficial as changes occur slowly over time.


Tanita | FAQ
Which just goes to show you that these scales arent as accurate as the calipers method. Because levels of water in the body can affect the reading, it really makes it a guesstimate. Maybe measuring twice per day - in the morning after going to the restroom AND in the evening before going to bed.

We have one of those Tanita scales and I never use it. Have no idea what my body fat is (too high I know) but as long as I can see my abs and the "V" Im okay.
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Old 04-02-2010, 10:18 AM
 
Location: Tucson
42,846 posts, read 52,681,702 times
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Quote:
Originally Posted by LaoTzuMindFu View Post
Which just goes to show you that these scales arent as accurate as the calipers method.
Eh, that's for the truly obsessed. I can't quite figure out the 105 lbs "fat" people, though...
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Old 04-02-2010, 05:43 PM
 
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I was probably on the slightly dehydrated side when I took the test. I had exercised a couple hours before. Being dehydrated would tend to underestimate body fat, as I understand how the process works.
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