First placed on the Internet February 2003|
Modern society has a serious problem of childhood obesity. Here is a method that can greatly contribute to a solution! In five minutes of fun, a child can determine her average body density to a precision of one part in a thousand!
A week later, or a month later, if she has eaten carefully and/or exercised, and therefore reduced her bodyfat by a tiny amount, so her average body density is greater by even one part in a thousand, she will know that there was an improvement! From a kid's perspective, a lower letter Baton or larger Float was used, which means WINNING! Yay!! The incentive and motivation for a good diet and exercise is wonderful! Quick and accurate feedback is extremely important for anyone to stay with a good diet. Adding in fun and competition is a bonus!
If a parent has to "force" kids to do something "that's GOOD for them" it will probably rarely work! This activity is FUN, and even somewhat COMPETITIVE! Except for REBELLION, it is everything that kids stand for! The premise here is that kids will WANT to do this activity, and the parents are the ones who might get "dragged along". We think that this is a key to providing enduring motivation for kids to become more aware about their diet and exercise. (It works just as well for parents!)
We have a picture-board sequence of a Simple and Accurate Bodyfat Measurement - PSA Storyline Childhood Obesity Public Service Announcement (PSA) which should soon be running on many television stations.
Here are also some streaming video files of the PSAs:
Most children will WANT to have their bodyfat percentage measured every week or every month! They will find it fun to do. More importantly, many of them will use their childhood competitiveness to develop interest and attention to their diet and exercise, so they can "show off" that they are lowering their bodyfat percentage! The idea of "winning" is really important to kids, and it can even help them develop positive self-images. This weekly testing can become a competitive game for them! We think that many are even likely to turn down junk food, to make sure they "win" in competition with a sibling or friend!
A simple, extremely accurate and inexpensive system for monitoring body fat content has not been available before. The system described here is certainly simple! One of a set of precision "Baton" weights (identified by letters) or similar Floats, is used in any shallow swimming pool to achieve "neutral buoyancy" where the person (and weight/float) then neither sinks nor floats. Given the Letter of the weight/float used, a pre-calculated Analysis Chart (which looks like a multiplication table) then directly reads off the precise bodyfat percentage, for a given (dry) weight on a standard scale. Most importantly, the results are extremely accurate and repeatable, so that an individual can chart progress regarding reducing bodyfat content, often even better than ±1% accuracy! Wonderful feedback is available quickly, and it is extremely accurate. Motivation naturally follows in most kids and people.
This approach is a simple, fun and safe variation of the long highly trusted and respected "Hydrostatic Weighing" method, that has long been considered the "Gold Standard" of methods to measure bodyfat. Hydrostatic Weighing is the only method that consistently gives accuracy of around ±1% (or better), sufficiently good to chart progress. Unfortunately, the traditional Hydrostatic Weighing technique requires extensive and expensive equipment, costs more than $30 for each test, removes a (public) swimming pool from any other use for an hour, and is extremely uncomfortable and stressful. This new approach avoids all those disadvantages while retaining the extreme accuracy. The pre-calculated Charts often provide an accuracy and precision, which is easily repeatable, of well better than ±1%.
Public Services Home Page
Television stations should soon start running PSAs (Public Service Announcements) on this method of combating Childhood Obesity. Up above on this web-page, there is a link to the story-line of one of the PSAs.
There are several methods that are much more precise, but they have tended to involve extremely expensive equipment ($10,000 or $30,000 or $1,000,000). One of those accurate methods, called Hydrostatic Weighing, has long been referred to as the "Gold Standard" of these methods because of its excellent accuracy.
The new system being presented here is a unique new method of applying the hydrostatic weighing method, but far less expensively and far more comfortably.
Before we proceed, we want to make some observations about the methods mentioned above:
In the legal disclaimer for such devices, it refers to the need for an experienced tester to do the test and evaluate the results. This is intended to minimize variations in the amount of skin being squeezed and the amount of pressure applied with the device. If a person could always duplicate those things, then moderate accuracy is possible, but more importantly, REPEATABLE moderate accuracy might then be possible. However, due to those two effects, it has been well documented scientifically that a person can get a reading as much as ±15% (higher or lower) than the true value of bodyfat percentage.
There are many other sources of error as well. If a person had done specific exercises to tone the muscles in that area, much lower values might be read, even if none of the rest of the body had been developed or affected. Similarly, if a person just "pulls in the belly" by tensing the abdominal muscles, the reading can become far off. If the person had just been running, or sitting, those muscles are in different states of tautness, again affecting the results.
The low cost of such devices provide a quick and entertaining result, but it is virtually meaningless, BECAUSE OF THE LARGE ERROR FACTOR. At a County Fair, have you ever spent a Quarter on an "IQ Tester" or on a "Love Meter", that claims to provide accurate results? Did you believe it was accurate?
There is such a device being sold on the market that claims a precision of around ±1.1% "as compared to the Gold Standard Hydrostatic Weighing technique". That is simply not possible. The manufacturers of such devices insist that the accuracy of results depends on the skill of the tester. That is certainly true! But in a different way than it sounds. An experienced tester will look at the person to be tested, and immediately get an idea of about what bodyfat percentage to expect. Then, if they use the calipers and see some DIFFERENT reading, they simply ask to do another test. It only takes a few seconds, and so the person being tested simply assumes that the tester is committed to getting an even more accurate result. No they aren't! They will adjust the amount of skin measured the second time, or adjust the amount of pressure applied, to get a reading which matches what they expect! So, in the manufacturer's laboratory, IF a testee is FIRST identified as having a (hydrostatic measured) bodyfat percentage of 23%, there is little doubt that an "experienced tester" could quickly get a reading remarkably close to 23%! It doesn't prove anything! Such trickery simply provides a reason for many people to buy such a device and also provides a legal defense for any challenges against their claims. This is America and we see such things in commercials for many things! Now, if such tests were done through a small hole in a wall, where the tester could not actually see the testee, and if no PREVIOUS bodyfat percentage was known, THAT could represent an actual scientific evaluation of such devices. It does not appear that any such serious testing has yet been done.
It is pretty obvious that such an approach cannot be very reliable or very accurate. A slender bodybuilder (actual bodyfat maybe 11%) and a flabby out-of-shape person (actual bodyfat maybe 35%) could have the same height and weight, and so BMI sees no distinction between them!
The BMI approach is by far the simplest, so it has quite a bit of popularity. In 5 seconds, anyone can determine his or her BMI. For a long time, it has been known that the BMI method is regularly very far off for many different groups, such as children, women, blacks, etc. The tester is supposed to make corrections, or use different charts, for all the various groups. This adds in even more potential error, because the tester's judgment about using various charts can drastically change the results. Like both of the methods above, readings of ±15% above or below the actual reading are fairly common.
It is well known that fatty tissue has a lower density than lean tissue or bone or even water. It happens that bone and lean tissues have higher density than (fresh) water while fat has a somewhat lower density than (fresh) water. As a result of the fact that we all contain some amount of fat, most people will float in fresh water. We even float higher up in water that has salt in it, because salt water has a higher density than fresh water, which makes our bodies even more relatively buoyant.
Using a method first derived by an ancient Greek 2300 years ago, it is possible to determine the AVERAGE body density by completely submerging the person in a pool or tank. There are a couple approaches to this: (a) measuring the amount of water displaced, which equals the volume of space the body takes up, and dividing that into the dry weight to get average density; or (b) precisely weighing the (always reduced) underwater weight of the person, to use a formula to then calculate the volume or average density directly. In principle, (a) could be as simple as filling a barrel absolutely to the top with water and then carefully getting in, and having all the overflow water go into a measuring container. However, when this is done, water is splashed and spilled, and even a teaspoonful of water lost can affect the results. There is even a new variation of (a) where the AIR displaced by a person's body is measured/calculated, inside a complex and expensive Pod, but that approach has some sources of its own errors. An extended discussion of that method is included in the version of this presentation that is intended for adults, linked below.
Once that AVERAGE density has been determined, some assumptions are applied and then some simple algebraic formula can be used to give the relative amounts of high density (muscle/bone/etc) and low density (fat) in the body. This is essentially the basis of the Hydrostatic Weighing method.
The usual actual hydrostatic testing process is nearly gruesome! Witches in Salem didn't have it much different! Few people are ever willing to have it done a second time! A person is generally charged between $30 and $40 each time they want to use this method to determine their bodyfat content. They also must sign a legal waiver before the testing! The procedure generally takes around an hour to complete, and a health club or YMCA must have staff occupied with this procedure, and the equipment is extremely expensive (around $10,000), so lower fees are not realistic. A strong chair is suspended by a cable and hoist and a precision weighing scale over a swimming pool or similar tank. The swimming pool must not have anyone else swimming in it during that hour, since wave disturbances would push the chair around and change the scale readings. Most reputable operations also have a Medical EMT nearby, but they tend to keep that person out of view, so as not to scare the person too much! The person is thoroughly strapped to the chair, not unlike an electric chair! This can be extremely stressful to the person, especially when they realize that they are about to be lowered beneath the water. Just before the person's head goes below the surface, he/she is told to expel ALL the air in their lungs, and then the chair is lowered further so the person is fully submerged.
An extremely accurate weight scale is attached to the cable, which measures the underwater weight of the combination chair/person, very accurately. Generally, it takes around 30 seconds for waves and chair motions to stop enough to get a constant reading on the very sensitive scale. The person must not move around (part of the reason for the straps) or else the reading would be valueless and the process would have to be repeated. Once a steady reading is obtained, the chair is raised back above the surface. The person has been underwater for around 45 seconds, AFTER having expelled all the air they could, and often coughs and gasps as soon as the mouth is above the water, This procedure, with empty lungs, is extremely stressful physically. It is also very stressful mentally, as the person generally fully realizes that his/her life is completely dependent on the person operating the equipment and the proper functioning of all the equipment. If even the slightest thing binds up or otherwise goes wrong, the person has very serious problems regarding survival. Health clubs generally require a person to sign a legal waiver (lots of fine print) prior to this procedure!
Having this done once would be bad enough! But it turns out that slight variations on how well a person expels air from the lungs can have significant effects on the results, so the accepted method involves repeating this process from seven to ten times, which generally takes around an hour to accomplish. Personally, I am somewhat amazed that people PAY $30 to $40 to have this done to them!
However, the results are very accurate, generally better than ±1% repeatability. If the measured value is 20% the person could be confident that the actual bodyfat content on that day was likely to be between 19% and 21%, which represents very useful information.
A health club must consider the potential liability issues, as some people panic when completely helpless underwater strapped to that chair, and CPR and other medical attention has been known to have been necessary. In this, it has worked out to be a real advantage that generally only very fit, athletic people tend to have such serious interest in bodyfat content to pay $30 to $40 to have it measured. Each person must pay a significant amount of money, and experience substantial discomfort, in order to get these accurate results. The liability issues and the high cost of the equipment have caused relatively few of these systems to be installed and available. Even when a Club has already bought the equipment, they rarely want to tie up their entire pool for an hour for a single test, and the wages of several staff workers, as well as the time required to set the equipment up and take it back down.
Some variations of the Hydrostatic Method are sometimes used. A special stainless steel tank is sometimes used, which is less uncomfortable because waves caused by the person in that small tank tend to cancel out more quickly. In some cases, the person is not even strapped to a chair and could reach for the edge of the tank if panic occurred. However, that tank tends to be extremely expensive and it permanently takes up valuable space in a Health Club, and its mechanism and water require regular maintenance, so few Health Clubs choose to get it.
Now, you do the exact same thing, except this time, you first exhale ALL the air you possibly can before doing it. You may still float, but now your friend will notice that you float lower in the water. Or you might now sink. This is because you do not have all the buoyancy of the air in your lungs increasing your "displacement" (volume) of water. Your body weight has not changed, and so your average density (weight divided by volume) is now higher so it is now much closer to the ACTUAL average body density. There is still some air in your lungs, which cannot be expelled, and there is also air inside your intestine, but there are mathematical adjustments that can be made to correct for those effects.
Next, your friend will hand you one of the precision Baton weights or precision Floats. You will now do the exact same procedure, exhaling all the air you can, and curling up in a tight ball again, but now you will be holding the Baton weight or Float against your belly. Depending on which size weight she handed you, you may now (a) sink to the bottom; (b) remain floating with part of your back out of the water; or (c) float just below the surface, or very slowly sink or rise, sort of hovering.
Notice that your head is only underwater for a few seconds, and that you are not strapped to anything, and that you are in the shallow end of the pool. At any moment, you could just stick your feet down to the bottom and instantly get your head above the water. And that you can even hold your nose!
The first time you would do this, you may need to try several different of the precision Baton weights or Floats, but after a few tries, you would know which specific (letter) Baton weight or Float was about correct for you. You could then take a Baton or Float where you are just barely floating and do this several times, each time trying to expel more air from your lungs. The more you can expel, the more likely you would sink with a specific Baton weight or Float. If you find that you can learn how to expel enough to clearly sink, which is essentially WINNING, you might try the next lighter Baton weight or larger Float. (A lighter Baton weight or a larger Float will give a lower Bodyfat Percentage number.) Your friend could make notes about each try, but once you sink, you could consider trying the next lower letter Baton or larger Float.
This makes it into sort of a game! Next week, when you check your bodyfat again, you will do everything you can to be able to use one letter lower Baton or larger Float and still sink! You can try as many times as you wish (at 5 to 10 seconds underwater at a time) and if you ONCE manage to sink, you have succeeded!
What you are really accomplishing here is creating "neutral buoyancy". The combination of you and that specific precision Baton weight or Float would have exactly the same as the 0.9978 gm/cc density of the 72°F fresh water in the pool. (actually, fresh water has a density of 1.0000 gm/cc but only when it is at 39°F), identical to the water. That is why you neither sink nor float. Since the Baton weight or Float is accurately known, some pre-calculated algebra gives your bodyfat percentage directly, read from a simple Analysis Chart.
Now get out of the pool because we are ready to get the results! Or, switch places so your friend can learn his/her bodyfat percentage, and have as much fun as you just had!
The set of precision Baton weights and Floats comes with several Charts, (linked in this web-site) which look like multiplication tables, where all the Algebra has already been done for you. The Charts have body weight as each column and baton letter as each row. The girl in the pool found her weight (80 pounds, dry, as above) could have neutral buoyancy with the (old and now obsolete) & float and 'F' precision Baton weight. On the Analysis Chart, you would just look at the column "80 lbs" and go down to the row "&+F" and find 25.2% (By the way, that represents 20.2 pounds of body fat, a very healthy amount!) (Our newer Bodyfat Calculator can no longer analyze using that obsolete '&' float!)
Here are guidelines from the American Council on Exercise (for adults).
|Obese||32% up||26% up|
So, such a value would be excellent Acceptable level, nearly Fitness, for a woman or a girl.
When that girl comes back a week later and is able to sink with the 'E' Baton, she can be confident that her bodyfat percentage has ACTUALLY lowered by around 0.7%. This is incredibly useful information, and it is due to the extreme accuracy and repeatability of this system. It is therefore VERY realistic for a person to do such testing each week or each month, and chart the results. If the resulting graph shows a downward trend, the person is certainly reducing bodyfat percentage!
This system is SO accurate that the guidelines given for standard Hydrostatic Weighing are appropriate, if the person wants truly precise values. Hydrostatic Weighing is so accurate that if the person had eaten a meal that had created gas inside the intestine, the results will show a substantial difference! Regarding Hydrostatic Weighing testing, few people have been willing to have endured multiple testing, so the extent of this effect does not seem to have ever been fully studied scientifically. They had simply found that when people ate certain meals before being tested, the results were several percent off! So they simply instruct people to have specific meals in the hours before being tested. We agree with that, but can show why that is the case!
At some point this gas must escape, either through a belch, burp or flatulence. For this testing to be most accurate and most valuable, it is best NOT to consume any carbonated beverage for at least six hours before a test.
As noted, the first of these effects generally produces the most intestinal gas, and is also the most variable due to different types of food being eaten. It seems surprising but our US Government seems never have done any scientific studies regarding human flatulence! The best available scientific information is that a normal human body produces ABOUT 3/4 quart (24 ounces) of food- related intestinal gas every day. Someone has apparently found that an average human expels flatulence about 20 times every day. There does not seem to be any scientific way to verify these numbers, but we will accept them here for discussion's sake.
Let us consider a practical example! Say that the girl had enough intestinal gas in her to either belch or emit flatulence an amount of gas accumulated over about six hours, equal to the volume of a standard coffee cup (6 oz). This is not an unusual amount inside a person (maybe less inside a kid!) Six ounces of gas inside a person is about equivalent to a flotation baton that has six ounces of flotation, meaning that the person would wind up using a baton that was about four letters different than if there were no gas inside! This would then give a result (for our example girl above) that was 30.0%, around 3% higher than is actually true.
Now, for general information, a value that is off by less than ±3% is fine, but for people who want to chart their own personal progress, better accuracy is desirable. Therefore, whatever amount of intestinal gas a specific person normally has, if they eat similar meals and do bodily functions relatively similarly in the hours before a test, the intestinal gas content figures to be fairly constant, which allows the excellent precision of this method to display itself with Chartable results. Each week, their intestinal gas may affect their absolute value percentage (always upward) but the effect would be nearly the same each week, and so the points on their progress chart will all be similarly affected, and so any trend toward improvement will be clear.
We have tried to provide for those possibilities in the web-site calculator.
(Done with the scientific stuff!)
It does not seem actually desirable or necessary, but there are products on the market, such as Beano (which is based on an enzyme named alpha-D-galatosidase, which breaks down some polysaccharides), that claim to keep most intestinal gas from being formed. Also, most people knowledgeable about food know that some foods (like beans, cabbage, carrots, bananas, onions, etc) tend to produce a lot of intestinal gas, and they could be avoided in the meal before such a test, to aid in getting the best accuracy.
The result is that any person can realistically get ±1% repeatability and accuracy in weekly bodyfat results. A Chart of such weekly results would then clearly show any improvement or worsening of the bodyfat percentage. Such a Chart could contain some weeks where the data is a couple percent high (due to excessive intestinal gas that week) but a general trend would be obvious. With this Progress Chart as incentive, an added focus on diet, junk food and exercise is much easier to develop, and improvements are likely to follow.
There appear to be around 17,000 membership-based Health Clubs in the USA. There are also many other non-membership-based facilities that have swimming pools. That includes around 29,650 Public High Schools, 6010 Private High Schools, and 7,000 Post-Secondary Schools which have swimming pools. There are also many thousands of (summer) outdoor Municipal Swimming Pools. Our hope is that one of these pools is near to nearly every American and that they each make or get their own set of these Batons and Floats, so that everyone would have the chance to use a publicly-available set of this system for no more than a dollar cost.
The person being tested then does not have to put up $30 or $40, does not have to have any special skills or knowledge, does not even need to know how to swim, and does not have to be strapped to a chair for an hour, being at the mercy of equipment and workers who are strangers. This method is not only non-stressful, it is fun!
Clients have never had any way before of monitoring bodyfat content so accurately, without spending a small fortune on repeated drownings by the standard Hydrostatic Weighing method! Now they do, and it is even fun and easy and quick! Can you imagine the free local media coverage for a Health Club by reporters regarding such a free service to the community? Especially when it represents such a good tool for each individual to monitor and advance their personal health and that of their children. And the bonus of all the extra new Members that would join that Club, because of respect for it?
At a YMCA or Health Club, an individual could sign in to use the set of Batons and Charts, in the same way they check out a basketball. Very little specific help should otherwise be necessary. Even if there are questions, people already using another set of Batons would certainly be willing to explain or demonstrate anything!
For YMCAs and Health Clubs, we provide below the complete directions on how to create several different versions of the full set of precise baton weights, for FREE! The full sets of the filled-PVC baton weights could also be bought pre-assembled, and even pre-calibrated. Our hope is that NO end customers would ever have to buy or make such a set of weights, as long as a sufficient number of YMCAs and Health Clubs have them available.
Our hope is that every American will be able to track their own bodyfat percentage on a weekly or monthly basis, either for free or for a maximum of a dollar charge (if a person is not a Member of that YMCA or Health Club). We think that this extra awareness of an important health issue might remind people to eat healthier foods and to exercise. Since there is no down-side for anyone in doing this, except for a few minutes of time to do this testing, we hope that nearly everyone would want to regularly do this testing.
For a 100 lb person, bodyfat range about 5% to 60%, about ±5% accuracy
For a 200 lb person, bodyfat range about 9% to 60%, about ±4% accuracy
For a 300 lb person, bodyfat range about 16% to 60%, about ±3% accuracy
For a 100 lb person, bodyfat range about 5% to 60%, about ±4% accuracy
For a 200 lb person, bodyfat range about 9% to 60%, about ±3% accuracy
For a 300 lb person, bodyfat range about 16% to 60%, about ±2% accuracy
For a 100 lb person, bodyfat range about 6% to 60%, about ±2% accuracy
For a 200 lb person, bodyfat range about 9% to 60%, about ±2% accuracy
For a 300 lb person, bodyfat range about 16% to 60%, about ±1% accuracy
The associated Floats can be made of a standard piece of Blue Foam house insulation, using a standard hand or power saw, by nearly anyone, for around $10. If you and your family are not very close to obese, you might only need the Floats, and then this would all be extremely simple and easy to make! All the needed directions are provided here in an associated web-page.
For a 100 lb person, bodyfat range about 5% to 60%, can be ±1% accuracy
For a 200 lb person, bodyfat range about 9% to 60%, can be ±1% accuracy
For a 300 lb person, bodyfat range about 16% to 60%, can be ±1% accuracy
For a 400 lb person, bodyfat range about 19% to 56%, can be ±1% accuracy
For a 100 lb person, bodyfat range about 5% to 60%, can be better than ±1% accuracy
For a 200 lb person, bodyfat range about 9% to 60%, can be better than ±1% accuracy
For a 300 lb person, bodyfat range about 16% to 60%, can be better than ±1% accuracy
For a 400 lb person, bodyfat range about 19% to 56%, can be better than ±1% accuracy
For a 100 lb person, bodyfat range about 4% to 60%, about ±1/2% accuracy
For a 200 lb person, bodyfat range about 4% to 50%, about ±1/4% accuracy
For a 300 lb person, bodyfat range about 7% to 60%, better than ±1/4% accuracy
For a 400 lb person, bodyfat range about 8% to 49%, better than ±1/4% accuracy
For a 100 lb person, bodyfat range about 6% to 60%, about ±1% accuracy
For a 200 lb person, bodyfat range about 9% to 60%, about ±1% accuracy
For a 300 lb person, bodyfat range about 16% to 60%, about ±1% accuracy
For a 400 lb person, bodyfat range about 19% to 56%, about ±1% accuracy
Have a "normal" amount of air in your lungs, NOT having severely exhaled or inhaled. And then simply float stationary! Your friend sees (or maybe even measures) how much of your head sticks out of the water! If you do NOT float and sink toward the bottom, your bodyfat is likely to be around 13% or lower. If your friend sees TWO INCHES of the top of your head above the water, you are likely to be around 24%. If your friend sees about FOUR INCHES (essentially to the very top of the earlobes), you are likely to be around 40%. If around SIX INCHES (essentially to the earholes, and your eyes are above the water) then you are likely to be around 57%. You might see from the large changes in bodyfat numbers due to rather small differences in the amount of the head being visible, that this method is only very approximate, with ±10% being expected. It only provides a ball-park number!
We mention this because there are a LOT of people who have been told that they have 8% or 4% or 11% bodyfat, due to using the extremely inaccurate bodyfat caliper method or electrical impedance (methods absolutely proven to regularly be ±15% off either way, so in other words, meaningless except for bragging purposes.) A person could try to alter this method by intentionally normally exhaling first, which makes you float around one inch lower, which would appear to give an estimate of around 6% lower. By attempting to exhale all the air you can, you can lower your body by about 3 inches, which can give the appearance of around 16% lower estimate. The point is that by simply altering the amount of air in your lungs, you could change this reading by as much as 16%, another indication of why the far more accurate and repeatable Batons and Floats is desirable. If you really want to believe that you are at 8% or 11% so you can brag to your friends, there are many ways you can create such a number. However, if you actually want a REAL number for bodyfat, this very crude method can get you within about ±10%, and the Batons-Floats can get you within about ±1%.
Combating Childhood Obesity Through Motivation! (specifically directed at Childhood Obesity)
The Simple and Accurate Bodyfat Measurement - PSA Storyline of the 30-second and one-minute PSA (Public Service Announcement) TV presentations.
The page that provides the PVC construction details for the Batons
and Floats and all the printable Analysis Charts is at:
Bodyfat Analysis Weights - Filled PVC Plastic Batons http://mb-soft.com/public2/bodyfwp2.html
The page that provides the construction details for the Pepsi bottle-based
Batons and Floats and all the printable Analysis Charts is at:
Bodyfat Analysis Weights - Pepsi Bottles and Pennies! http://mb-soft.com/public2/bodyfwp3.html
The page that has the Determining Your Accurate Bodyfat Percentage Bodyfat Calculator which uses the Baton/Float letters and the dry body weight
C Johnson, Theoretical Physicist, Physics Degree from Univ of Chicago