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  #1   ^
Old Wed, Jun-19-02, 14:08
wbahn's Avatar
wbahn wbahn is offline
Senior Member
Posts: 5,334
 
Plan: Atkins-ish, post-WLS
Stats: 377/214.5/177 Male 72 inches
BF:
Progress: 81%
Location: Colorado Springs, CO, USA
Default Body Fat Scales - Are they worth it?

NOTE: This has actually turned into a much broader post - the Body Fat Scale stuff is near the bottom.

Most of us need some means of measuring our progress - either to make adjustments to our program if needed or just to reassure us that things are going well. But what should that measurement be?

Scale weight?

It's the easiest measurement to take, but it has lots of pitfalls just waiting to snag us.

First - what's your goal weight? This is not too serious an issue - at least at the beginning - because we really are only looking for progress at this point. We can pick a goal weight off a chart somewhere or remember a weight at which we felt good or shoot for the weight that a friend is at. The point here is that it is pretty easy to come up with a specific target weight and work towards it knowing we can always change the goal later.

Then, the measurements themselves generally have enough error to cause some people a hopeless amount of frustration - especially if we don't have a good scale. You can find out a bit about what makes a scale good by looking at: Accuracy and Precision of Weight Scales

But even with a good scale it is difficult to interpret the measurements in an accurate and meaningful way. The scale may not budge or might even go up for a few weeks even though you might be losing fat during that time. This can be caused by a combination of muscle building and water retention in the now empty fat cells. So unless you are comfortable with this and can truly accept it, the misleading behavior of the scale readings might lead to dispair and abandonment of your efforts.


Body Measurement?

This is a much better indicator of progress than a scale is - but it has drawbacks as well.

First - what's your goal? As with scale weight, we are really only looking for progress initially but at some point we need to start moving toward our final, long-term goal. This is much harder. I have an idea of about where I would like my waist size to end up, but I have much less of an idea where I should aim for in terms of chest or hip size and absolutely no idea about what my final thigh or calf size should be.

Then, there are some of the same issues that can frustrate scale weight users - but not as many. If you build replace fat with the same volume of muscle, your scale weight goes up considerably but your inches would remain the same. More typically, you might build enough muscle to show a scale weight gain - or no change or only a slight loss - but your fat loss would be enough to show a discernable inch loss. That's good. But if your fat cells are holding on to water to keep their volume up, that fat loss would still not show up in your inch measurements. So these can still be misleading and frustrating if you aren't willing to take them with a grain of salt and exercise patience and persistence.

Body Fat Percentage?

This is a pretty good measure of progress - IF you can get good numbers. That's where the problem is.

First - what's your goal? This is not too tough as there are quite a few good tables of ideal body fat percentages and they are in pretty good agreement with each other. And, as with any of these, you are looking for progress at first and can change the target goals as you get closer.

But now we need to have a way to actually measure body fat percentage. Good luck. The only really good way to measure body fat percentage is to strip the fat off and weigh it. While that works fine for cadavers (and this is how all other methods are calibrated when all is said and done) it would have long-term health implications for you or me. We need a non-destructive means of estimating body fat percentage fo us.

The Gold Standard for these measurements are the hydrostatic tank measurements where your overall body density is measured directly. But these are not without error primarily owing to imperfect knowledge about such things as bone density and bone volume. So your frame size is usually estimated by taking wrist or elbow measurements and your bone density is estimated by looking up your racial make-up on a chart. After doing that, you get a pretty decent number. More importantly, you get a number from which future changes can be compared and that's what is really important for a long time.

But hydrostatic body fat measurements are difficult to make, require special equipment that is hard to find, costs quite a bit of money (more than you would want to spend to get weekly or monthly measurements) and are inconvenient and time consuming. So we need something else - preferably something we can do ourselves at home.

There are LOTS of formulas out there for estimating body fat percentage using a combination of your weight and key body circumference measurements. Some are better than others but all are pretty shakey as far as accuracy goes. But, as we have found with every other measure - accuracy is not terribly important as long as we have good enough precision (repeatability) to let us see changes over time. As long as we use the exact same method and forumulas every time, this type of measurement can serve us well provided we do not try to put to much faith in the actual number that results.

In a similar fashion, skin fold measurements can be used to estimate body fat percentage and the have all of the same issues. In addition, getting repeatable measurements on yourself or on someone that is considerably overweight can be very difficult whereas girth measurements are pretty easy to make. On the flip side, once you get reasonably close to goal, skin fold measurements taken by an experience technician yield reasonably accurate results.

Finally, we come to the Bioelectric Impedance Analyzers (BIA). These come in two varieties (as far as I'm concerned): Laboratory Grade and Consumer Grade. To understand the difference, let's first discuss what BIA is and how it relates to body composition.

The basic idea behind BIA is that the electrical impediance (resistance) of fat is different from that of muscle and bone and blood and other body structures. So, if we measure the body's electrical impedance we can gain insight into the relative quantities of these various substances. So far so good. But there are real problems both with taking a meaningful measurement and with making a reasonable interpretation of the results.

First we have the same issues that the hydrostatic tests have and we need to make adjustments based on bone size and bone volume using charts and tables.

In actually taking the measurment, we have to overcome the skin resistance - which dominates the overall resistance. Consider tha most people, with dry skin, can get somewhere around 100V across their body (say wrist to wrist) and won't even feel any sensation - the body's resistance is sufficiently high to limit the resulting current to a level below our sensation threashold. Now consider that if you get past the skin resistance by piercing the skin with a needle in each wrist then a 9V battery is more than sufficient to deliver a lethal current.

In addition to the dominating nature of the skin resistance - skin resistance is highly variable. The quality of the contact, the surface area of the contact, and the degree of moisture on and in the skin at that moment all have a major impact on the effective contact resistance.

To get around this problem, Laboratory Grade BIA instruments use four wires. Two generate the actual current and the other two, located on the body between the other two, measure the voltage drop that is produced by the current flowing through the body. This is called a four-wire measurment and is the only reliable means of getting around both skin resistance and lead-wire resistance.

Furthermore, once we get current into the body, we have to ensure that this current flows through a representative cross-section of the body. This normally entails injecting current into one ankle and extracting it from the opposite wrist. That way it travels through one leg, the abdomen, the chest, and one arm. Any measurement that goes foot-to-foot or hand-to-hand is going to be seriously flawed right from the beginning.

Finally, the distance between the electrodes and the cross sectional area of the body structures through which the current is flowing are important and are measured during Laboratory BIA tests.

If all of these factors are taking into account and good measurements are made using several thousand dollars worth of equipment then BIA measurements can produce results almost on par with hydrostatic measurements.

So, what do Consumer Grade BIA instruments measure? To be frank, I haven't the faintest idea! They are all two-wire measurments, they all use a non-representative cross-section of the body, all of them neglect electrode distance and limb cross-sction. About the only thing most of them can possibly be measuring is skin resistance. Some of them try to play some games to subtract this out, but the methods used are generally pretty suspect. This is why an obese person can sometimes obtain a lower body fat percentage reading than a skinny person and why a given person's measurements generally vary all over the place from day to day and week to week.

So, my recommendation is to not waste your money on any consumer grade BIA devices.

So what should you use? Personally, go by how you feel first off. Then, use your clothes as a guide - the infamous pant-o-meter. Third, track your key measurements and pick one type of body fat measurement technique (usually, the more complicated the better) and run those numbers every few months. Finally, the scale is quite useful IF you can use it only to track the long-term trends and can ignore the short-term (month or less) fluctuations.
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  #2   ^
Old Wed, Jun-19-02, 18:13
fridayeyes's Avatar
fridayeyes fridayeyes is offline
Senior Member
Posts: 2,044
 
Plan: low glycemic
Stats: // Female jkl
BF:
Progress: 69%
Default

You know, I might even go for the 'strip off the fat and weigh it' method on one condition...

...that they don't put it BACK!! lol

Cheers!

Friday
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  #3   ^
Old Wed, Jun-19-02, 19:56
razzle razzle is offline
Senior Member
Posts: 2,193
 
Plan: mostly paleo
Stats: //
BF:also don't care
Progress: 100%
Location: West Coast, USA
Default

bill, thanks so much for doing this. (you remembered! ) You put a lot of volunteer work into this, and I am grateful, as others will doubtless be for far into the future. (assuming we get this linked onto the newbies' stickie, hint hint!)
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  #4   ^
Old Wed, Jun-19-02, 23:00
SlimShAdY's Avatar
SlimShAdY SlimShAdY is offline
Senior Member
Posts: 986
 
Plan: Atkins for now.
Stats: 135/?/115? Female Short. 5"3
BF:Don't wanna know.
Progress: 15%
Location: RI
Default

I don't believe in them scales. Like it actually can tell the difference between 100lbs of fat or 100lbs of muscle. Umm
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  #5   ^
Old Sat, Jun-29-02, 01:29
stingraywe's Avatar
stingraywe stingraywe is offline
New Member
Posts: 5
 
Plan: Ketogenic Diet
Stats: 187/167/155
BF:31%/23%/10%
Progress: 63%
Location: Albany, NY
Default

Bill,

Thanks for such a great deal of information. I have been using a Tanita body fat scale (model TBF-604) and have found it to be incredibly useful as a method of gauging progress.

How do I know how accurate it is? I don't really. However, I have found the scale to be extremely consistent, and that is what is important. By weighing myself at the same time every day under the same conditions on the same scale, I can view my progress in relative terms.

So, if the scale tells me my bodyfat% is 22%, I really don't know how accurate that is (maybe it's only 19% or it oculd be 25%). However, if a week later it is telling me I'm now 21%, I can have a fairly good idea of my progress - and that's all I really need to know.

I've found Tanita brand scales to be very consistent. While the old spring style scales are completely worthless, the better strain gauge scales seem to be quite consistent. I can get on and off the scale 20 times in a row and it will give me the exact same results every single time.

So, in my opinion, finding a decent quality body-fat scale which yields consistent results should be an adequate way of gauging progress. While it may not be 100% accurate (in my opinion it's probably quite accurate as well), I think for the average person it is certainly adequate.

The key really is not necessarily paying too much attention to the total weight, but to the fat %. Also, these numbers can fluctuate quite a bit from day to day, so comparing weekly or bi-weekly results may be better.

I've also found that if you use one of these body-fat scales, you should keep your feet dry. I always weigh myself first thing in the morning to keep results consistent. One time for the fun of it I weighed myself after coming out of the shower with my feet totally wet. The results were WAY different! My bodyfat% with dry feet was 26%, but with wet feet it came out as 19%. Huge difference!

Dean
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  #6   ^
Old Thu, Mar-06-03, 16:09
RodeRash's Avatar
RodeRash RodeRash is offline
Registered Member
Posts: 98
 
Plan: modified CDK
Stats: 182/174/168 Male 69 inches
BF:19%/17%/15%
Progress: 57%
Location: Northern Colorado
Default Tanita scale.

I have a Tanita body fat scale. I think it is a great tool for gaging your progress. After I had it for about a month, I did an underwater body fat check, and the results were the same.

As stated in the instruction manual. Your body fat reading will vary at different times of the day. It depends on how hydrated you are. More than likely, your state of hydration would also affect an underwater weight test, but probably not as much.
In the morning, when you first get up, you will get the highest body fat reading of the day. (as well as the lowest weight).
I have found that my weight varies about 3 to 4 pounds through the day, and the body fat indicator will change as much as 2 percent.
I also found that you can drop your body fat percentage a full point if you check right after you get out of the shower, and you are still a little damp.

I check my body fat and weight the first thing in the morning, before I shower because I get the most consistant (if not the most flattering) readings.

Last edited by RodeRash : Thu, Mar-06-03 at 16:10.
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  #7   ^
Old Sat, May-24-03, 17:43
2bthinner!'s Avatar
2bthinner! 2bthinner! is offline
Senior Member
Posts: 3,345
 
Plan: Paleo Gluten free
Stats: 242/216/130 Female 5'7.5"
BF:too/dang/much
Progress: 23%
Location: Florida
Default I don't know how accurate it is either

but it actually puts me at a higher percentage than the measurement method. And one BMI tool, which takes your height and weight, has me at 30%. I'm using the 36%, possibly 35 or 34 now. It honestly seems like the more accurate of the three.. It gives me a point to work from, and shows changes in nice little digital numbers. I don't have to remeasure all my parts, and look up its meaning in little charts.
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  #8   ^
Old Sat, Jun-21-03, 10:27
timco timco is offline
Senior Member
Posts: 195
 
Plan: Atkins / Protein Power
Stats: 215/152/150 Male 68 inches
BF:
Progress: 97%
Location: New York City
Default

Consumer Reports reviewed body fat scales a while back. They recommend anything by Tanita. They do caution that these scales tend to overestimate body fat percentage (I think the average overestimation was about 5% for women, 2% for men), but that they were accurate in measuring results over time (i.e. the actual body fat percent may be a little bit off, but the amount of body fat lost from one weigh-in to the next should be accurate).
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  #9   ^
Old Wed, Oct-29-03, 11:19
catfishghj's Avatar
catfishghj catfishghj is offline
Senior Member
Posts: 428
 
Plan: atkins
Stats: 330/217/190 Male 70 in
BF:?/30/less than 20
Progress: 81%
Location: Tucson, AZ
Default

I bought one, I dont remember the brand ($50 at KMart), and my BF varies from 28 to 32%. I am not too worried about this variation, i just bought it because I like gadgets. The scale part I am very happy with. It seems very accurate and repeatable.
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  #10   ^
Old Mon, Feb-16-04, 12:49
cbcb's Avatar
cbcb cbcb is offline
Senior Member
Posts: 791
 
Plan: South Beach-esque
Stats: 194/159/140 Female 5'3"
BF:34% / 28% / 20%
Progress: 65%
Default

Anyone have a problem with their Tanita scale? Mine stopped displaying fat percentage, just gives me a --- --- --- kind of reading, after (accurately) displaying weight. (None of the other settings have changed)
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  #11   ^
Old Wed, Mar-03-04, 23:01
hairpin's Avatar
hairpin hairpin is offline
Contributing Member
Posts: 424
 
Plan: Atkins
Stats: 147/128.5/120 Female 5'3
BF:29%/28%/20%
Progress: 69%
Location: San Francisco
Default

This sounds silly of me to ask... but you don't happen to have socks on while you're trying to measure do you?
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  #12   ^
Old Wed, Mar-03-04, 23:26
cbcb's Avatar
cbcb cbcb is offline
Senior Member
Posts: 791
 
Plan: South Beach-esque
Stats: 194/159/140 Female 5'3"
BF:34% / 28% / 20%
Progress: 65%
Default

Actually, no! Though it's true in the morning sometimes I have so little energy I'd be amazed I could carry an electric current at all!
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  #13   ^
Old Wed, Apr-14-04, 12:33
fridayeyes's Avatar
fridayeyes fridayeyes is offline
Senior Member
Posts: 2,044
 
Plan: low glycemic
Stats: // Female jkl
BF:
Progress: 69%
Default

bumping this
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  #14   ^
Old Fri, Feb-11-05, 15:00
lisammon lisammon is offline
New Member
Posts: 23
 
Plan: -
Stats: -/-/- Female -
BF:
Progress: 58%
Default Body Fat Scales

I have a Soehlne "Atlantic" scale. The set up requires my height, sex and age. It has settings for 4 people. It measures weight, % body fat, and % water. That way you know if your body fat number is low due to excessive water or if you body fat number is high because you are dehydrated. A moderately hydrated reading is the most accurate. It is very consistant.

As to accuracy, I had a 4-wire measurement taken at a clinic and it showed a reading 6% lower than my home scale, BUT I ingested a lot of water beforehand. I general terms, I figure tracking body fat at home is a measure of change - up or down.

Additionally, one must remember that for the lean body fat percentages of athletes, there are different parameters and different scales.

Remember, when using an electronic impulse body fat scale, one must have arms and legs not touching and slightly bent knees. AND make sure the scale and your feet are dry.
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  #15   ^
Old Mon, Aug-06-07, 11:57
davidcoast davidcoast is offline
Registered Member
Posts: 36
 
Plan: Peskin
Stats: 195/167/165 Male 72 inches
BF:
Progress:
Default

I have also had good results using a commercial grade Tanita Fat Analyzer at my local pharmacy. By weighing myself at the same time every day and measuring my impedance on the Tanita every month I have found a slow but consistent decline in body fat mass percentage. My last reading on the Tanita was 7.3%. This is consistent with my body shape (I now have an hourglass waist with my abdominal muscles clearly visible) and other fat measurements I have had taken in the past.

I also use the pant tightness test as well as taking waist/hip measurements from time to time. However, if my stomach is flat and well defined I consider this to be a good indication of my fat content. It is also common for people to comment that I am slim (in the waist). In summary, no single measurement is completely reliable. A number of indicators that are in agreement is more reliable.
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