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From Fellrnr.com, Running tips
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Body fat scales can provide a cost-effective and convenient way of measuring body fat. It's best to get fat scales that measure from both the hands and feet, rather than from either the feet or hands alone. Also, consider [[Skulpt]] which is an alternative way of measuring body fat.
=How They Work=
Bioelectrical Impedance Analysis (BIA) scales use an imperceptible electrical signal to calculate the amount of water in the body and thus estimate body fat. BIA compares the electrical resistance of a direct current to an alternating current. The direct current does not penetrate the cell walls whereas the alternating current does. This creates a difference that allows an estimate of extracellular water.
Hydration can have a significant impact on the reading, so readings need to be taken at the same time of day with the same level of hydration. The [[Book Review - The 4 Hour Body|4 Hour Body]] recommends drinking 1.5 liters (3 pints) of water, waiting 30 minutes, urinating and then taking a measurement. I have found that with the whole body scales I can simply measure when I wake in the morning and I get a consistent enough reading to not require this hydration procedure. The biggest problem for an athlete is that BIA is particularly inaccurate when fat free mass, including [[Glycogen]], changes<ref name="BIA1"/><ref name="BIA2"/>. I've noticed that the day after a long run, the scales claim a much larger loss of body fat than is reasonable. Studies have shown that obesity is underestimated with many body fat scales.
==Optimizing Accuracy==
My approach to optimizing my scales accuracy is average and calibrate. My Tanita BC-601 scales offer several activity levels, so I find the level that matches a more accurate body fat measurement such as a [[DEXA| DEXA Scan]]. I then use an average of a week's readings to even out any hydration errors.
==Posture and Accuracy==
With BIA scales it's important to get the posture just right, as even small variations in the position of your arms can make a significant change to the reading. You must hold the handset with your arms at 90° with your elbows straight.
[[File:Omron HBF-510 posture errors.jpg|none|thumb|x300px|Posture errors.]]
|}
=Glycogen Changes=
One study<ref name="ShioseYamada2018"/> concluded that changes in [[Glycogen]] storage shouldn't change body fat estimates using bioimpedence.
=Recommended Scales=
I have tried a number of scales over the years and I believe the Omron HBF-510 516 is the best value for money, but the Tanita Segmental scales may worth the extra cost for their improved accuracy. I would avoid any scale that only measures via your feet.
==Best Value - Omron HBF-516==
The Omron HBF-516 offers great value for money and are one of the cheapest BIA scales that measure from the hands and feet. It's not segmental, so you only get an overall body fat estimate, and it's only single frequency, but it's really cheap. In fact, it's cheaper than a lot of feet-only body fat scales, though unlike Tanita scales, it's not FDA approved. There's no recording of the data, so you'd need to write down the results to track your weight and fitness. There's a 180-day memory, so at least you wouldn't have to do that every day, but I'd still recommend transferring the data to something that will graph your data. <jfs id="B001803OS6" noreferb="true"/>. Omron makes a few variants of this scale, such as the HBF-514C <jfs id="B0020MMCDE" noreferb="true"/> (90 day memory), HBF-510W <jfs id=" B001IV61J4" noreferb="true"/> (white, no memory). [[File:Omron HBF-516.jpg{{BuyAmazon|center|thumb|300px|]]AZN=omron body fat scales}}
==Segmental - Tanita FitScan BC-601FS==
The BC-601F is one of the cheaper Tanita single-frequency, segmental BIA scales and it will record your data onto an SD card. This is far less convenient than a Smartphone app, but it's a lot better than writing things down each day. <jfs id="B016APIYQK" noreferb="true"/>.
[[File:Tanita FitScan BC-601FS.jpg|center|thumb|300px|]]
==The Best – Tanita RD-545IM==
The Tanita RD-545IM is the first consumer grade dual frequency segmental scale. The dual frequency gives increased accuracy, and the RD-545IM even claims to estimate Muscle Quality and measure resting heart rate. The RD-545IM uses a smartphone app, which is nicer than an SD card. Unfortunately, the RD-545IM is not yet released, but should be available soon.
[[File:RD-545IM.jpg|center|thumb|300px|]]
==Comparison Table==
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"
!
! Omron MBF-516
<ref name="BIA1">Body composition changes assessed by bioelectrical impedance measurements http://www.ncbi.nlm.nih.gov/pubmed/2923071</ref>
<ref name="BIA2">Changes in fat-free mass during weight loss measured by bioelectrical impedance and by densitometry http://www.ncbi.nlm.nih.gov/pubmed/2912008</ref>
<ref name="ShioseYamada2018">Keisuke Shiose, Yosuke Yamada, Keiko Motonaga, Hideyuki Takahashi, Muscle glycogen depletion does not alter segmental extracellular and intracellular water distribution measured using bioimpedance spectroscopy, Journal of Applied Physiology, volume 124, issue 6, 2018, pages 1420–1425, ISSN [http://www.worldcat.org/issn/8750-7587 8750-7587], doi [http://dx.doi.org/10.1152/japplphysiol.00666.2017 10.1152/japplphysiol.00666.2017]</ref>
</references>
