Best method to measure bodyfat at home?

jim180155
jim180155 Posts: 769 Member
edited November 8 in Health and Weight Loss
I've been measuring my bodyfat using a bioimpedance scale since January 2013. It's not a perfect method, but it's been good for tracking the overall trend over time. A couple months ago I bought a set of calipers for skinfold tests. The set came with a tape measure, so I started using that as well. It took a few weeks to get consistent with the way I was measuring, but I think I've got that worked out.

A lot of people here have strong feelings about different methods, with bioimpedance scales being generally knocked for inaccuracies. This morning I started wondering if people could pick out the methods used based on my actual results over the last six weeks, or at least whether or not they could pick which result came from my bioimpedance scale. (If bioimpedance scales are that inaccurate, it should stand out, right?)

My basic stats: 60 yrs old, 149.4 lbs, 5'9" tall, recent pic in my profile. The four sets of results below are using a bioimpedance scale, calipers for suprailiac 1 point test, calipers for 3 point Jackson-Pollack test, and tape measure for 8 point test. Can you pick out which results for the last 6 weeks go with which method?

Method A: 11.4%, 11.6%, 10.8%, 10.3%, 9.0%, 9.2%
Method B: 11.1%, 11.4%, 11.6%, 10.4%, 10.8%, 10.0%
Method C: 14.6%, 14.6%, 14.6%, 14.6%, 14.6%, 14.6%
Method D: 12.7%, 12.4%, 12.4%, 12.7%, 12.7%, 13.3%

Replies

  • leftcoastscott
    leftcoastscott Posts: 3
    jim180155 wrote: »
    A lot of people here have strong feelings about different methods, with bioimpedance scales being generally knocked for inaccuracies.

    They get knocked for inaccuracies over populations that vary due to a host of factors outside an individual's control. They can be fine for particular individuals at particular times, the trick is you don't really know if they're accurate for you unless you compare the results to something like a DEXA scan. In your case, with around a five point range among your measurements for a given week, you can probably narrow down the one or two best methods for you by looking at one of the online photo arrays, I suspect that'll be more effective than asking random people to play a matching game.

    Generally, for measurements that have a lot of "noise" - which includes pretty much any home-based attempt to track weight or bodyfat, unless you've invested in some fairly high-end equipment - you're much better off looking at averages and trends than individual points. Get 50 or 60 data points, look at rolling averages and the rate of change between them over time, and you'll be starting to accumulate some useful data.
  • jim180155
    jim180155 Posts: 769 Member
    No one? Come on, this should be easy. Just pick the most inaccurate method.
  • williams969
    williams969 Posts: 2,528 Member
    Take the average of them. That's what I do. Well, I don't have a BI scale, so I only do 1-point test and *very* careful tape measurements (I take average of the Navy method and Covert Bailey formula).

    My numbers for each of the methods is always within 2-3% of each other, but also show a general downward trend, which is all that matters.

    If you're asking which to consider, I'd toss the BI numbers (way too many variables affect those readings for some people), and average the rest to get your "number".
  • jim180155
    jim180155 Posts: 769 Member
    edited November 2014
    williams969 wrote: »
    If you're asking which to consider, I'd toss the BI numbers (way too many variables affect those readings for some people), and average the rest to get your "number".

    This is the kind of comment I'm talking about. Why would I toss my BI numbers when they are as consistent as any of the other methods?

    I'm starting to think bioimpedance scales are like politics or religion. People are going to believe what they want to believe regardless of any contrary evidence.

    This is the scale I use:

    amazon.com/Omron-HBF-514C-Composition-Sensing-Monitor/dp/B0020MMCDE/ref=sr_1_1?ie=UTF8&qid=1415475477&sr=8-1&keywords=omron+514+scale

    It takes readings through your hands and feet at the same time, which theoretically gives you a better result for overall bodyfat. I don't know if it actually works better than other BI scales, but it seems to work pretty well for me.


    I agree that BI scales can be inaccurate, but the main variable is hydration, and that's pretty easy to control for: you take a reading first thing in the morning after peeing, before you've had anything to eat or drink. If you've been fairly consistent the day before with sodium levels, that also helps. If you've had a lot of sodium, your weight will be up while your bodyfat percentage will be down. Your readings will come back into line after the sodium has worked its way out of your body. If you eat a lot of sodium just about every day, then your readings will be off, but they'll be consistently off. It's not rocket science. But if you can't follow the instructions that should come with the scale, you might think it's the scale's fault.
  • SlaughterHouseFive
    SlaughterHouseFive Posts: 24 Member
    jim180155 wrote: »

    If you eat a lot of sodium just about every day, then your readings will be off, but they'll be consistently off.

    The excess sodium skews the result in which direction? More body fat or more lean mass?


    I'll pick Method D for BI and C for tape measure. What did I win Jim?
  • jim180155
    jim180155 Posts: 769 Member
    Slaughterhouse, you won a new Camaro for having the guts to venture a guess. Please drive down to your local Chevy dealer and tell them I sent you. They'll give you the keys on the spot. Just make sure you know what color you want before you ask for the keys.

    Sodium makes you retain water. BI scales measure electrical resistance in the body. Lean body mass, including muscle, contains a lot of water while fat contains little or no water. Water is an excellent conductor of electricity, meaning that it will present little resistance to the flow of electricity. So the less fat in your body, the less resistance to the electrical signal that the scale uses. The way it works in real life is that you might step on the scale after a high sodium day and find that you weigh a couple pounds more than you did yesterday due to the extra water. But it's not all bad news because your bodyfat percentage might read a couple points lower due again to the extra water. If you didn't know better, you might think you gained 2 pounds of muscle overnight.
  • Zedeff
    Zedeff Posts: 651 Member
    I think that bio-impedance scales are very useful for measuring intra-individual changes over time. In theory the algorithm used by any given scale will have a fixed error rate - maybe off by 0-5%. This error rate however may be deviant from the absolute truth, but as the algorithm of the scale doesn't change over time, it should be highly reliable.

    In other words, these scales are likely to be precise but not accurate. For following a trend over time, precision is all that you really need.

    On a different note, thanks for linking to your scale - I think I'm going to buy one. I'm not entirely sure why Amazon offers to sell them as a 2 pack though - why would anyone need 2 of the same scale?
  • jim180155
    jim180155 Posts: 769 Member
    edited November 2014
    Do not buy the 2 pack! I don't know what they're doing with that option. You can buy one for $62.52, or two for $165.04 which is $82.52 each. I wonder how many people fall for that one.

    I agree with your overall assessment of BI scales, Zedeff. They're great for measuring trends. They're also the quickest and easiest method of getting a reading. Because of that, I take daily BI measurements.

    Calipers and tape measures are a lot cheaper though. Here's the caliper I bought and it came with a free tape measure. I'm not sure if they're still including the tape measure or not: amazon.com/Accu-Measure-Fitness-3000-Personal-Tester/dp/B000G7YW74/ref=sr_1_1?ie=UTF8&qid=1415489537&sr=8-1&keywords=bodyfat+caliper

    I later bought a digital tape measure, which is still relatively inexpensive, but much easier to lock in your readings. (You'll know what I mean by that if you ever try measuring the circumference of your own neck.) Here's the digital tape measure: amazon.com/Health-Meter-Digital-Measure-HDTM012DQ-69/dp/B008CENXCS/ref=sr_1_1?ie=UTF8&qid=1415489781&sr=8-1&keywords=digital+tape+measure

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