I have one of those $100 dollar Tanita body-fat scales (1 decimal poing precision). I measure my BF% along with my weight every morning and write down the numbers into an Excel worksheet so that I can graph my Lean Mass and Fat Mass as a function of time.
Anyway, the thing is, this scale is doing “magic” things. As my physics lab instructor likes to say “we HATE magic in here when we’re trying to take quantitative measurements”. Incidentally, that’s what I’m trying to do.
Some observations:
The air temperature seems to affect the body fat %. If it’s colder, I need to stand on the metal plates for about 2 minutes just to warm them up to get an accurate fat % measurement. The funny thing is, the fat % actually goes DOWN each time I take a measurement, sometimes by as much as 0.5%. So what I basically end up doing is taking 10 measurements and writing down the lowest one. This is a pain in the ass. Does anyone here have a better idea to handle the temperature drip?
I’m really glad that you asked. Temperature plays a huge role in this test. At my old house, I used to do it first thing in the morning (before a shower) while standing under the heat lamp in my house. Temperature in my place was pretty consistent and I never saw a problem. Well, at my new place, temperature control is non-existant, so during the warm months this was not a problem, but with the cold weather starting, this was beginning to affect my readings. Basically, the skin is constricting and the peripheral vessels are constricting to maintain body temperature. This will clearly affect your conductance and your impedance measurement.
For the past several weeks, I've now only been doing measurements after I take a shower in the morning. I'll take a shower, completely dry off, throw on a T-shirt and some boxer briefs and then get on the scale. Now, things are looking great again. I always throw out the first measurement and then take a few more until the reading stabilizes, usually 2-4 times. So give this a shot and let me know how this works for you. Just make sure that you are fairly dry - a little moisture on the hair is still ok and that you keep everything as consistent as possible.
Question on these home scales. I don’t think they’re all that accurate for measuring absolute bf, but are they good for relative changes? So if I measured 17% two months ago and 11% today, could I be confident that I lost 6%BF?
I have found those things to be highly inaccurate, especially if you are carrying a good deal of muscle tissue. The ones you stand on seem to be confused by the water in muscle tissue. Regardless of whether you use the “athlete” version, I returned mine after it kept jumping around within the same minute to 3 totally wide ranged body fat percentages. The only ones that I have found to be accurate are the handheld electrical impedence machines.
I have a tanita scale and I question its accuracy. The scale says I have 29% BF. The other day I had a personal trainer do a pinch test and came up with 17% BF. Are either right or something inbetween.
I remember looking at Tanita scales at one point and honestly thought that unless the ‘top end’ scales were bought, the other’s wouldn’t be accurate enough. I used a ‘basic’ stand on version and found the calculation parameters too general i.e couch potatoe or olympic athlete. My BF% swung from 7% up to 15%. The better options I found for using electrical impedence is by lying down (less resistance for current) attaching low voltage wires to foot & hand and using calculation software to provide readout. Be interested to know what you other guys think. Didn’t mean to hyjack your thread.
Bioimpedance is really a difficult subject to tackle. It may work well for some but not for others, but the same goes for any technique to measure body composition.
When you maintain control over as many variables as possible - time of day, hydration status, ambient temperature, etc., you can get reliable results (meaning it can track changes and will give you consistent results if there are no changes to track). Bioimpedance is just a tool that requires a bit more understanding of the underlying technology to work well.
I use both a Tanita and an Omron Handheld as a “double-check”…and have been pleased for a couple of years now…
One thing to keep in mind…ANY measurement (see Jason’s article) is going to have some difficulty and inaccuracies ESPECIALLY if you’re looking for some “absolutes” for bragging purporses (…“I’m 2% BF, man…”)
I use them to measure RELATIVE progess…and I agree with Prof…the handhelds, like the Omron, show much less fluctuation.
The human body is 70% water. A lot of that is stored in muscle…the more muscle, the more water. If you have any amount of “decent” muscle (bodybuilder) the bioelectric impedance is uselesss
While I understand what you may be trying to get across, I disagree. I would like to hear your argument, but you’ll need to expand significantly to prove your point.
Even the manufacturers agree the bioelectric impedance is not valid for bodybuilders. The average person is 70% water,bodybuilders tend to run at about 75%. The logarithym in the computer is set to calcuate impedance of current at 70% (water conducts current, fat resists)The best results I get (I am a fitness director of a major health club),Is from a skyndex caliper (durnin formula)…PS mineral also conduct ,if you are super hydrated one day and dehudrated the next, dont’t expect anything consistant
I agree with you that skinfolds will provide the most consistent data and are the best method for most of us to use to track body composition. And while I also understand that impedance devices are not the optimal system, they can be very effective and also very useful for monitoring hydration status and body composition. Bioimpedance devices are devices I would only recommend for personal use as you need to have control over factors such as time of day, temperature and hydration status. But with smart planning, you can consistently get very reliable results.
As for the body water issue, there are already too many assumptions that all methods for body composition rely on to consider any of them accurate beyond a complex 4 compartment model that also has its problems. I've presented my argument on this issue in my article in issue 208 if you care to read it.
In a health club setting, it would be reckless and irresponsible to use bioimpedance as you have no control over the person being measured. Skinfolds are a much better choice and I thoroughly agree with you on that and that is why I recommend them as the method of choice in the article series I wrote for T-Mag.
I actually looked into working with the Bod Pod manufacturers, but I still think skinfold measurements are a better choice overall in the health club, they just may not look as flashy. The Bod Pod is nice, but suffers from many of the same problems that bioimpedance does in terms of practicality - ambient temp, skin moisture, and clothing problems. It also has a few of it’s own - you have to sit still for a couple of minutes, claustrophia is a real concern, the puffing motion to measure lung volume can be difficult for some, ambient pressure needs to be controlled (no opening of the room door during the procedure) and it is way more expensive.
Anyway, I'm not trying to belabor this thread, I just want to make it clear that all methods have their drawbacks and their advantages.
I think that taking a weekly BF% with the tanita is useless. So I measure every day… what I did was make an Excel spreadsheet as follows: Date, Weight, BF%, Lean Mass, Fat Mass. This allows me to graph the Leat/Fat mass as a function of time. And when you LOOK at the data, you can plainly see the average Lean mass & Fat mass, which is approximately your “real-relative” LM / FM. In a world of imperfection, this is the best compromise. Unless you want to get dissected :0)
Harkonnen - well said. That is exactly what I do and have been recommending for a while. I even go so far as to average the Mon - Sun readings into my one weekly measurement. I still keep all the daily measurements, but I refer back to the weekly average to track my progress. I’ve (and others) been using this method for over a year now with good results. Unless I do something to cause a huge hydration shift, my max variation on body comp data is consistently within 1% and usually even less.