Body fat percentage is one thing that many people take great concern in, and there are a number of ways sold by the fitness industry, medical sectors, and insurance agencies that are proposed to give you your exact measurements. Unfortunately, the easiest, most available methods of measuring one's body fat percentage are, generally, the least accurate. Here, I'll list the several methods of measure.
Body Mass Index
One of everyone's favourites (for some reason).
Body mass index is simply a formula that takes your heigh and weight to give you a number that places you somewhere on the BMI scale. The formula for this is:
mass(kg)/(height(m)[squared])
While used very, very widely by many organizations, it is being generally accepted by professionals that this is a very, VERY faulty method to measure one's body composition. Why? Because when using a person's body mass to calculate the BMI, there is no way to differentiate between how much of that mass is fat and how much is muscle. Basically, if a person is extremely tall and has a high body fat percentage, then her or she might be scored to be in shape. On the reverse side, the BMI scale is notorious for calling short, muscular people obese. If anyone ever takes their BMI rating, I do not recommend taking it to heart.
Bioelectrical Impedance
Sounds fancy, right? Well, not so much. This is the method used by many people at home, using those scales that send an electrical signal up through the body. The information feedback to the scale about how conductible your body was to the signal is supposed to determine the amount of you that is body fat. There are fancier, more expensive machines that come with hand grips that will give a supposedly more accurate reading as well, and some that are only a handheld device without the scale beneath your feet.
Unfortunately, this can be an extremely inaccurate way to measure body fat percentage. You will receive a different reading based on how hydrated you are, as well as what you may have been eating recently. (There's no real agreement by the experts on HOW water and food affect the reading, but it's clear that they, in some way, do.)
While being impossible to get a single, valid reading of your body fat through this method, it IS possible to get a general idea of your body fat range. If you take your body fat reading this way at the same time every day, while you are well hydrated and haven't eaten anything too heavy recently, your readings over the course of a week or so can sort of give you an idea of your range.
Skinfold Testing
This is a slightly more valid method of testing body fat. Note, however, that by valid, I mean that it's consistent and reproducible, but not necessarily accurate.
The skinfold technique involves using a caliper to pinch certain, predetermined areas of your skin and measuring the amount of fat beneath it. The problem with this method, however, is that is can ONLY measure the subcutaneous fat (skin fat) and will not give you any reading about your visceral fat stores (deeper fat stores surrounding your organs). Furthermore, even when just looking at the skin fat, people's bodies all store fat in different places.
As for the actual test, the thing with the skinfold test is that it takes a LOT of practice for somebody to be able to measure it correctly. (I, for instance, had an entire class on it and still haven't gotten it completely down.) Also, if one is to take a skinfold test more than once, it has to be the same person performing it every time, as having a different person take it for you will result in the skinfold being taken in slightly different spots, resulting in inconsistent results.
Hydrostatic Weighing
This was once the "golden standard" for body fat measuring, and is still one of the top methods. However, this method is expensive, requires professionally, the facilities, and takes a lot of time.
The way this works is that a person is completely submerged into water and empties his or her lungs of air as much as possible. After that, your weight while being underwater is measured in relation to how deep you sink. (Fat is more buoyant, if anyone has forgotten.) This will provide one of the most accurate body fat percentages available today. Unless the person being tested has a medical condition that affects his or her weight in relation to their volume, (osteoporosis, for instance) this is one of the most recommended methods for anyone.
Dual Energy X-ray Absorptiometry
Myself, I am not extensively knowledgeable in this particular method, as it is still fairly new, but this is supposed to be the new "gold standard".
DEXA sends two different x-ray signals into the body, one which is absorbed more by fat than the other, which then are calculated by the computer to determine the total body fat percentage. This method is very accurate and only takes about 10-20 minutes. However, like hydrostatic weighing, it isn't very available to the public and is very expensive to have performed. On the plus side, if a person has a condition that would affect hydrostatic weighing, such as osteoporosis, then this method is the more ideal of the two.
So there you have it. Those are, generally, the most common forms of measuring one's body composition. Unfortunately, it remains that there is no cheap, easy way to get an accurate reading of body fat percentage, and the most available ways tend to be greatly flawed, but at least this gives you an idea of how to interpret your results if ever you do perform these tests.
Body Mass Index
One of everyone's favourites (for some reason).
Body mass index is simply a formula that takes your heigh and weight to give you a number that places you somewhere on the BMI scale. The formula for this is:
mass(kg)/(height(m)[squared])
While used very, very widely by many organizations, it is being generally accepted by professionals that this is a very, VERY faulty method to measure one's body composition. Why? Because when using a person's body mass to calculate the BMI, there is no way to differentiate between how much of that mass is fat and how much is muscle. Basically, if a person is extremely tall and has a high body fat percentage, then her or she might be scored to be in shape. On the reverse side, the BMI scale is notorious for calling short, muscular people obese. If anyone ever takes their BMI rating, I do not recommend taking it to heart.
Bioelectrical Impedance
Sounds fancy, right? Well, not so much. This is the method used by many people at home, using those scales that send an electrical signal up through the body. The information feedback to the scale about how conductible your body was to the signal is supposed to determine the amount of you that is body fat. There are fancier, more expensive machines that come with hand grips that will give a supposedly more accurate reading as well, and some that are only a handheld device without the scale beneath your feet.
Unfortunately, this can be an extremely inaccurate way to measure body fat percentage. You will receive a different reading based on how hydrated you are, as well as what you may have been eating recently. (There's no real agreement by the experts on HOW water and food affect the reading, but it's clear that they, in some way, do.)
While being impossible to get a single, valid reading of your body fat through this method, it IS possible to get a general idea of your body fat range. If you take your body fat reading this way at the same time every day, while you are well hydrated and haven't eaten anything too heavy recently, your readings over the course of a week or so can sort of give you an idea of your range.
Skinfold Testing
This is a slightly more valid method of testing body fat. Note, however, that by valid, I mean that it's consistent and reproducible, but not necessarily accurate.
The skinfold technique involves using a caliper to pinch certain, predetermined areas of your skin and measuring the amount of fat beneath it. The problem with this method, however, is that is can ONLY measure the subcutaneous fat (skin fat) and will not give you any reading about your visceral fat stores (deeper fat stores surrounding your organs). Furthermore, even when just looking at the skin fat, people's bodies all store fat in different places.
As for the actual test, the thing with the skinfold test is that it takes a LOT of practice for somebody to be able to measure it correctly. (I, for instance, had an entire class on it and still haven't gotten it completely down.) Also, if one is to take a skinfold test more than once, it has to be the same person performing it every time, as having a different person take it for you will result in the skinfold being taken in slightly different spots, resulting in inconsistent results.
Hydrostatic Weighing
This was once the "golden standard" for body fat measuring, and is still one of the top methods. However, this method is expensive, requires professionally, the facilities, and takes a lot of time.
The way this works is that a person is completely submerged into water and empties his or her lungs of air as much as possible. After that, your weight while being underwater is measured in relation to how deep you sink. (Fat is more buoyant, if anyone has forgotten.) This will provide one of the most accurate body fat percentages available today. Unless the person being tested has a medical condition that affects his or her weight in relation to their volume, (osteoporosis, for instance) this is one of the most recommended methods for anyone.
Dual Energy X-ray Absorptiometry
Myself, I am not extensively knowledgeable in this particular method, as it is still fairly new, but this is supposed to be the new "gold standard".
DEXA sends two different x-ray signals into the body, one which is absorbed more by fat than the other, which then are calculated by the computer to determine the total body fat percentage. This method is very accurate and only takes about 10-20 minutes. However, like hydrostatic weighing, it isn't very available to the public and is very expensive to have performed. On the plus side, if a person has a condition that would affect hydrostatic weighing, such as osteoporosis, then this method is the more ideal of the two.
So there you have it. Those are, generally, the most common forms of measuring one's body composition. Unfortunately, it remains that there is no cheap, easy way to get an accurate reading of body fat percentage, and the most available ways tend to be greatly flawed, but at least this gives you an idea of how to interpret your results if ever you do perform these tests.
I just learned how to effectively take skinfold measurements last week. I find it pretty easy to take a measurement now, but it's tough to stay consistent with each trial.