Why you don't like your body comp numbers.

Body composition is an inexact science. The only truly valid way to measure body composition is by dissection and I’m very sure no one wants to participate in a validation study comparing method X to dissection. Therefore, you need to find a method that is reliable. Reliability is the how well a a measurement can be duplicated over and over again. Accuracy is really not as important as you may think. First of all, body composition measurement is something we use to track our progress in the gym. Even if our measurements are a few percent off from what our real body composition are, we can look at the changes that are occuring to our fat mass and muscle mass.

Therefore, we need a way to check our body comp frequently, reliably and conviently. Contrary to popular belief, hydrostatic weighing is not nearly as accurate as you may think. We have cadaver dissection data on 51 cadavers, but it is really not that comprehensive. Most equations that are used today for converting your body density measure from hydrostatic weighing to %body fat relied on 3 male cadavers ages 25, 35, and 46. It also can be quite unreliable. For example, if I was to measure your body composition first and then have you sit in a sauna and lose 1 kg of water and then measure you again; that 1 kg water loss would show up as a loss of .5 kg fat free mass and .5kg fat mass, even though it should be a loss of 1kg fat free mass. Also, unless you work at a facility or lab with a hydrostatic weighing tank you won't be able to be measured frequently enough and you also cannot do it yourself. Other methods such as DXA, Bod Pod, and various other nuclear techniques are also expensive, need multiple people, and cannot be done frequently.

So that leaves the typical body builder with 3 realistic choices. The best choice of these methods will be the one that is reliable (gives you the same measure day in and day out assuming that you are not actively changing your body comp), the one that can be done alone and the one that is least expensive.

Choice 1 is girth measurements and %body fat equations derived from these measurements. This does not work well for bodybuilders due to the constant increasing in girths due to increased muscle mass. It works well for other things just not keeping track of body composition.

Choice 2 is biolectrical impedance (i.e. the Tanita scales and hand held analyzers). This can be ok, but only if you measure yourself at the same time under the same conditions. Fluctuations in your hydration markedly affect your measurements. So this can work, but measure yourself at the same time of day wearing the same amount of clothes each time.

Choice 3 is skinfold measurements. This is probably the most misunderstood measurement. All skinfold measurements have been derived by regression equation compared to hydrostatic weighing. But whereas hydrostatic weighing is markedly affected by day to day fluctions in hydration, skinfold measures of %body fat are not that affected by hydration. Skinfolds are also inexpensive (Accumeasure makes a decent one that is less than $15). They can be done alone (use the 3 site equation at the web site) or be done with your training partner (use the 7 site equation). After you practice a bit, you will find that your measurement technique will get pretty good and thus you won’t have a lot a variability if you are only measuring yourself or your training partner. For the equations go to this great site that I got from a Kelly Baggett post: Bodyfat Calculators push page
For women out there, you are going to need a partner to do both equations (3 and 7 site).

In conclusion, most methods are expensive and really don't allow the bodybuilder to utilize them well because they are also inconvenient. Skinfolds allow you to track your body comp as often as you want for a minimal expense. And my final advice: pick one method or one skinfold equation and stick with it. Don't ever mix methods unless you want frustration and bad data. Good luck. - Jason N.

Jason: I can’t tell you how BADLY your post was needed! Every week there is somebody obviously frustrated with not only the measurement they get but the device they use. Then someone comes along (QUITE incorrectly) and states “how accurate this is” or “this product is crap!”

If okay with you (and maybe you could do the same)I would like to see your response stored (in say a “Word” document) so that it can be pasted when the next frustrated MuscleHead posts about their body fat percentage and what product is most accurate. Outstanding post!

Great post. I agree that duplication is more important accuracy for almost all bodybuilding applications since we are looking for trends more so than an absolute number. Calculating lean body mass (lbm) for the purpose of determining caloric needs is the only application that I can think of in which accuracy would be more important than duplication.

Mufasa - will do. I have just completed my Master’s thesis where I compared DXA to several different reference methods. After my data collection and a thorough literature review, you can see my opinion above. I just want to shed some light on this somewhat confusing issue.

I agree with you about calculating LBM for caloric needs, but I also think that a good skinfold measurement will always have you somewhere in the ballpark (within 5 lbs or os of LBM). Also with all the slop in calculating acutual caloric intake, I think that the feedback from weekly body comp measures will provide the information to either increase or decrease calories.

I also think this was a great and long overdue post. I was wondering if anyone has heard of the fat track digital calipers. I saw them on a website and they were only $35. Has anyone tried them?? Good or bad?? I am only concerned because I am going to start the growth surge and I want to ensure I am taking in the appropriate calories. Thanks…

I just want to add my voice to the general chorus proclaiming Jason N. to be a minor deity. Very good points made, both in the original post and the follow-up comments. Mufasa, nice idea about the text file. We should probably do that for a lot of other issues that come up regularly as well, i.e. does masturbation hurt your T-levels, how do I gain weight, etc. Once again, nice post.

I don’t see any reason why those calipers would not work. I’ve never used them before, but like I said, as long as your consistent in how you use them, you should not have a problem. Good Luck.

Jason: Excellent post. This subject has come up so many times in the past week or so that I’m out of fingers counting. I do disagree with one small point: I think it’s beneficial (for peace of mind for nothing else) to get as many of the different methods done as you can get ONCE a year or so within as short a period as possible (certainly no longer then a few hours). This is just to set a baseline so you know the range your playing in, and to get it out of your head that the calipers or equation is accurate (if your 3/7/9-site equation is way off from the other two, it’s probably not a good one for your body type or you haven’t practiced enough taking the measurements). Then after that, stick with one method (most likely the calipers).

Jason N: Why don´t make a little longer articel and send to TC ? I think there is something similar somewere in the arkives but I like to read something over and over again to get it to stuck in my slow brain.

Jason: Not a bad idea from Z…all T.C. can say is “yes”, “no”, or “maybe…”. It’s worth a shot…

Thanks for the input everybody. Actually after reading the “Reader Mail” section, I got the same idea about expanding this a little bit and inserting the references. Hopefully, I’ll have it done by the end of this weekend. To Steve-O, if you want to get your measurements done with a variety of methods then go ahead, but the only way for most people to have access to many of these methods is to pay megabucks or get involved in a research study. Hey, if you can get into a reasearch study, then absolutely go for it. If you work in an exs phys lab, then go for it. If you have to shell out a couple hundred bucks, then buy some AP, Surge and MAG-10. Thanks again for the input and we will see what TC has to say. -Jason N.

Jason: I don’t know, but perhaps I’m lucky in the so-cal area to be able to get the hydrostatic weighing pretty reasonable - it was only $30 at the local university, which I guess qualifies for being in a study of some sort. For those that are interested in such a thing, try a university with a physiology dept. (ours is an excersise and physiology dept. at SDSU). I personally only think it’s worth it only once a year or 2 years. As Jason said, the calipers are much more available, take much less time, and if your trained in it, very repeatable. For me, I just needed to be able to see how different all of the methods were, so I knew the calipers weren’t lying.

Steve-O: I guess that I though you were talking about getting your body comp done by several methods such as hydrostatic weighing (HW), bioelectrical impedance, DXA, Bod Pod and others. Regarding HW, it was once considered the gold standard, but there are numerous problems. First, did they measure you residual volume? A difference of 500 ml can through off the measure by 5% or more. Secondly, the equations used to convert body density to %body fat assume that you and I and every other man and women have the same proportions and densities regarding our lean body mass(LBM). The 3 main components of LBM are water, mineral, and protein. It is assumed that everybody’s LBM is 73.8% water, 19.4% protein, and 6.8% mineral. These assumptions lead to significant problems with regards to accuracy. Multi-compartment models which corret HW for the variations in total body water and mineral content much improve the accuracy, but are usually only done in research studies due to the high cost and labor involved. So, don’t believe what you hear about HW. I thought it was the best measure of %body fat with regards to accuracy until I did my homework and searched the literature.

Jason: Yeah, I only did the HW, and the place offered a somewhat fancy-ier bioelectric impedance. For me, the calipers (9 sites, done by a nutritionist who does it all day long), the HW and the bio-impedance were within 1%, which put my mind at ease. I believe they did do the residual volume for me (blow as long as you can into a bag that measures the volume I think it was), so that was covered. Certainly finding a bod-pod, dexa, etc. at a good rate is probably impossible, unless like you said your part of a study or something. Not to mention that the time spent is probably impractical.

Very interesting point about the HW though. I’ve said quite a few times that your body type has to match the equation for calipers to be accurate, but I hadn’t thought that you have to fit the mold for the HW too! I hadn’t thought that your hydration level could throw it off by that much (BTW, the bio-impedance machine that they put me on had a measurement for %H2O, but I don’t remember the reading, and of course that measurement is suspect too). Definitely submit an article to the mag, this is really good stuff!

Just wanted to tell you that there’s a BodPod in SoCal – Beverly Hills to be exact. It’s in a “Dr. Huizinga’s” office. It costs 100 dollars per test, and accordingly, there was no line outside the Pod on the days I went. If memory serves, it was the only BodPod in SoCal, and maybe in California, as of a year ago. Unfortunately, I didn’t cross-reference the BodPod results with any other test. I can only say that the figures came to within 2% of what I might have estimated. Anyway, you’re in SoCal with a knowledge of the subject, so I wanted to mention it in case you didn’t already know. (And I’m assuming you know about the “Fitness Wave” truck for HW.)

Steve: Thanks for the info… I seem to remember hearing about the BodPod up in Beverly Hills, but haven’t really pursued it myself. I’m in SD, so it’s a bit of a drive when I can get the HW only 10 minutes away (and don’t have to deal with the 405 traffic!!!). Actually, I haven’t heard of the wave truck - guess they don’t have it in SDSU or Colgan’s place (they supposedly had a HW tank too, but it was too difficult to get in touch with them compared to the university, which I already had the contacts in). So what is it?

HW and the Bod Pod are basically the same method. Both of these techniques measure body volume. Body weight divided by body volume = body density. Body density is then plugged into an equation to determine %body fat. The company that manufacturers the Bod Pod was started by two grads from UC-Davis (my alma mater) and much of the original validation and comparison was done at UC-Davis also. The Bod Pod and HW are very comparable, but one is not really better than the other, because they both measure the exact same things and really on the exact same assumptions that I mentioned above in my previous posts.

Bottom line, don’t do both.

Fitness Wave is a mobile unit (read: truck) equipped with a dunk tank. It visits health clubs and measures the members’ BF. (And you don’t have to be a member – just make an appointment and meet them at the club.) It’s forty bucks per test, but you can get three tests per year for 80 dollars which comes to under 27 dollars per test. I think the closest they get to you is Orange County. Their website is getdunked.com. Anyway, all things considered, you’ve got it pretty sweet with HW facilities so close and reasonably priced.

Not to join the chorus of praise so late into the thread, but your posts are highly valued. And yes, T mag could use a thorough discussion of BF testing methods.

I’m trying to intuit my way through the following, without a scientific background, so thanks for being patient. You said that HW and the BodPod both measure body volume. When I think of the volume of an object, I assume that it’s measured by displacement. (That whole “eureka” story, right?) Now I can certainly see how the BodPod measures volume by air displacement in a sealed chamber. But when I get hydrostatically weighed, I don’t see water displacement being measured. Instead, I’m first weighed on land, and then, I get into a scale that lowers me into the tank, and I’m weighed underwater. So, not knowing any better, I assume that the disparity between land and water weight is the key factor, and I’m not sure what any of that has to do with volume. Nevertheless, on this forum, I’ve read that the idea of measuring “floating fat versus sinking lean” is not what HW is all about. And you seem to be agreeing with that. Indeed, if HW and the BodPod are using the same protocol, then HW can’t be about “floating versus sinking” at all. Again, this is just a non-scientific mind trying to puzzle it all out. Thanks for any light you may shed on this subject.