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Old 02-01-12, 10:40 AM   #1
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Scales that measure body fat... legit?

"Bioelectrical impedance analysis"

Specifically I'm looking at the Tanita Ironman BC-350 and was wondering if anyone might have experience with this scale.

It's tempting to be able to measure some of the metrics this scale offers:
  • Weight, Body Fat%, Body Water%, Muscle Mass, Physique Rating, Metabolic Age, Bone Mass, Visceral Fat
  • Basal Metabolic Rate (BMR)

But could they even be remotely accurate? This page suggests their measurements could be by as much as 5%. I don't consider that a big fluctuation.
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Old 02-01-12, 11:45 AM   #2
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Originally Posted by twobadfish View Post
<snip>as much as 5%. I don't consider that a big fluctuation.
It doesn't say if it's 5% body fat or 5% on the reading. I'm guessing it's 5% of bodyfat, which means it could tell you 20% when you may really be 25% or 15%.

This site paint a similar picture on Body Fat Scale Accuracy.

I guess it depend on why you want to know your body fat percentage.
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Old 02-01-12, 01:17 PM   #3
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Body composition scales are subject to a lot of variables. I have a Tanita Ironman and it is fairly consistent but still subject to wide variability. I know that sounds like a contradiction but let me explain. My morning BF% on most mornings is at 30-31% which is high according to my caliper based calculations, but every afternoon, my scale reads my BF% as 26-27% which is closer to the 25% I get by averaging 3x by caliper (which I do once a month). Every once in a while my scale will jump or drop by 3-5% for a day or two for no known reason without significant weight change. Electrolyte levels, skin moisture, hydration, even humidity can cause variances in readings with bioimpedence (bodyfat scales and handheld BF monitors). I think they are fine for spot checking and general trending, but I wouldn't count on them for high accuracy at any given time.

Don't obsess about the numbers (if you are weighing and checking your BF multiple times a day it qualifies as obsessing). Spot check your weight and BF every 1-2 weeks and watch for general trends. In between concentrate on how you feel, how you perform, and how you look (from a clinical not a narcissistic standpoint).
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Old 02-01-12, 02:11 PM   #4
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We just purchased an EatSmart scale (through Amazon) for $55. Works great. And it's made by a family firm in the USA. Bodyfat percentage is probably about 5% high according to skin-fold tests, but who knows for sure without an immersion test. You're supposed to check BF right before dinner and disregard the morning measurements. The main thing is to watch the trends. That's what it's for. Your actual number doesn't matter unless there's a medical reason.

I check my weight every morning when I get up. I think it's important to weigh yourself at the same time every day. Weighing yourself every day gives you a much closer insight into what your body's doing. Which of your lifestyle and athletic practices put on weight and which cause you to lose, and also your hydration status, are you swollen from a workout, etc.

These new scales also check your hydration and total muscle mass. I haven't had mine long enough to evaluate the usefulness and trending accuracy of these numbers, but I'm definitely going to check hydration before and after long rides. They also check bone mass, which might be useful over a period of a decade.
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Old 02-01-12, 09:26 PM   #5
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We have a Tanita at work. I got tested and was disappointed with the number (body fat %) after all my hard work. Then I got the "gold standard" water dunk task at a college sports facility.
It was much lower with the dunk test. your results might be different.

I have the sheets somewhere but it was like 21% vs 16%, so like 25 % lower (5 percentage points lower).

Even so, IMO, the scale would still be valuable to track your progress as the % moved etc.
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Old 02-04-12, 06:17 PM   #6
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I clip at 9.9%, but my Withings scale can vary between 12-16%.
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