Chris250
MuscleChemistry Registered Member
The Pro's and Con's of Different Body-Fat Measuring Techniques: An Explanation by Myosin (from PM)
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In college, I had the extreme pleasure, and fun, to work in the Human Performance Lab for a couple years. I was very fortunate to be exposed to a lot of different kinds of individuals, from the "Joes" to the Pro's and to a lot of different human performance testing. My two favorite area's- VO2 max testing and body-fat testing.
I'm not saying anything against the merits of getting your body-fat tested in itself, but rather, if you do get it tested, there are certain things you should know before you do. When doing anything scientific, there are key things you want to be aware of- validity (how accurate or truthful), reliability (how often you will get the same or similar results, its consistency), how many variables are involved, how much control over the environment, etc.
I'll give a brief summary of each test and my thoughts on them and then a final thought on them at the end.
Near-Infrared: It sends a light through typically one body part. How that light passes through is calculated in a formula for your body-fat.
Pro: To be fair, the technology is better than it was years ago. Extremely easy and fast.
Cons: There are just too many variables. Only uses one sight. Validity is poor.
Thoughts: I really wouldn't waste your money.
Bod-pod: Came out over 10 years ago (maybe 12?) and works in the same principle as hydro-static weighing (explained below): displacement of matter. You sit in an encapsulated "pod" in your skivvies and in less than a minute your body-fat is calculated. Was recently seen in a movie posted in a thread here at PM (something like, "I Want to Look Like That Guy in the Magazine").
Pro: All you do is sit . Fast and easy. You can use different testers and still get the same results.
Con: Still not very accurate, particularly if you are lean actually. It tends to give higher estimates on leaner individuals. Still has some kinks to work out.
Thoughts: Can be quite hard to find and a bit costly.
Skin-calipers: The most traditional method. There are several formula's used depending on how many sites are tested. Typically, the more sights tested, the more valid the test.
Pro: High validity. The more sights, the greater the validity.
Con: Variable reliability. A new tester could be quite inaccurate. Having someone different each time you go can also yield different results. If I'm remembering right, I was taught it can take up to 200 body-fat measurements for a tester to considered an expert.
Thoughts: Make sure to get tested by the same person each time, otherwise, two people can get different results. Make sure they use high quality calipers (Lange, Harpinden). Minimum amount of sights I would suggest- 6 (can go as high as 12).
Hydo-static weighing: Called the "gold standard." Before DEXA (explained below), this was considered the best method to have your body-fat tested.
Pro: Very high validity.
Con: TOO many variables, reliability can be poor.
Thoughts: Can be difficult to find. Cost might be a little high.
DEXA (Dual Energy X-Ray Absorptiometry): Could be called the "platinum standard." All you do is lie down on a table and a scanner goes over you from head to toe under a minute.
Pro: EXTREMELY accurate. It measures and divides out lean mass to the point of the mineral content in bones. It's also great to see just how much intra-abdominal or organ fat you have (HIGH correlation to early death and CHD).
Thoughts: Can be difficult to find. Cost can be prohibitive (a couple hundred dollars).
Final thoughts-
Infra-red: If this is something you might use on a regular basis, same time of day, it MIGHT be OK to use as a tracker, BUT NOT for accuracy. The problem though, let's be honest, A LOT of us here are quite obsessive-compulsive and seeing higher levels than what might actually be could be psychologically hard on some of us.
If anything, I would get my body-fat tested via calipers, then, immediately have it tested via infra-red. Then, use THAT number from the infra-red as your guide to track your progress.
Bod-pod: If there are more trusted methods available I would go with those. I would choose this over infra-red. Just the lack of availability makes this a poor choice.
Calipers: My choice. Cost is cheap and if you get the same experienced technician it has high validity and reliability. You can usually find this at a local university. Some community colleges might have it but their equipment might not be the best. But, in all honesty, there are some high quality plastic calipers and even if they use a 3 point method, the result won't be that far off than a high quality caliper, 6-12 point test (maybe 1-2% difference?).
If anything else, it's also great to help you know where you need to train a bit more. No, I'm not talking spot reduction, but re-composition… say your thigh measurement was 10mm, so you begin developing and building more muscle in that area. Now with the increase in muscle mass, your measurement is 8mm.
One controversial area (but growing in support) of knowing your measurements has to do with hormone imbalances. It's beyond the scope of this conversation, but there is some growing thought about body-fat levels in different places of the body and how different hormone levels affect those placements (Hawkmoon put up a study about this not too long ago).
Hydro-static: Even though it's the gold standard, here's the thing that really hurts this test you probably don't know. The original studies that were used to test the accuracy of this method were CADAVERS. Not a big deal in that, but, the problem lies in how the test is done. You sit on a seat connected to a scale in a tank filled with water, exhale all your air, sink down, hold your breath and try to hold VERY still as the scale "normalizes" on a number (when you sink down, the scale arm tends to bounce around a little bit). You do this several times and then take the average.
Here is the cadaver part and how it doesn't crossover very well with a live human…
Cadaver- All the air can be exhaled from them, so they sink fully. The tester can wait for the scale to settle before taking the final number.
Humans- A) it's very hard to exhale all the air from your lungs (it's impossible) so you always have a "residual tidal-volume" left over (which they try to educationally guess/calculate how much that is for your size).
B) Also, it's easy to fool yourself you got all your air out (I remember testing an "ultra-A type" from the Chicago Northshore and she floated like a balloon. I kept challenging her that she wasn't exhaling all her air and she in turn was becoming quite frustrated with me demanding she was. Her results turned out horrible- her body-fat was high but I know nowhere near what her test results were). You pretty much have to exhale all the way to the point of your chest hurting and almost passing out, seriously.
C) You need a VERY good tester. As mentioned, the scale arm bounces a little. For a live human, the arm never really settles exactly, so there is a bit of guesstimating of what the final number is. Trying to hold your breath for that long AFTER you honestly exhaled every bit of air possible is HAAARRRRRRD! You come up GASPING for air... and again, you do that several times!
DEXA: The sad thing is the cost. Even just from a health perspective it would be great to know and track how much fat you have around your organs. But, using this as your preferred choice is just not practical.
--------------------------------------------------------------------------------
In college, I had the extreme pleasure, and fun, to work in the Human Performance Lab for a couple years. I was very fortunate to be exposed to a lot of different kinds of individuals, from the "Joes" to the Pro's and to a lot of different human performance testing. My two favorite area's- VO2 max testing and body-fat testing.
I'm not saying anything against the merits of getting your body-fat tested in itself, but rather, if you do get it tested, there are certain things you should know before you do. When doing anything scientific, there are key things you want to be aware of- validity (how accurate or truthful), reliability (how often you will get the same or similar results, its consistency), how many variables are involved, how much control over the environment, etc.
I'll give a brief summary of each test and my thoughts on them and then a final thought on them at the end.
Near-Infrared: It sends a light through typically one body part. How that light passes through is calculated in a formula for your body-fat.
Pro: To be fair, the technology is better than it was years ago. Extremely easy and fast.
Cons: There are just too many variables. Only uses one sight. Validity is poor.
Thoughts: I really wouldn't waste your money.
Bod-pod: Came out over 10 years ago (maybe 12?) and works in the same principle as hydro-static weighing (explained below): displacement of matter. You sit in an encapsulated "pod" in your skivvies and in less than a minute your body-fat is calculated. Was recently seen in a movie posted in a thread here at PM (something like, "I Want to Look Like That Guy in the Magazine").
Pro: All you do is sit . Fast and easy. You can use different testers and still get the same results.
Con: Still not very accurate, particularly if you are lean actually. It tends to give higher estimates on leaner individuals. Still has some kinks to work out.
Thoughts: Can be quite hard to find and a bit costly.
Skin-calipers: The most traditional method. There are several formula's used depending on how many sites are tested. Typically, the more sights tested, the more valid the test.
Pro: High validity. The more sights, the greater the validity.
Con: Variable reliability. A new tester could be quite inaccurate. Having someone different each time you go can also yield different results. If I'm remembering right, I was taught it can take up to 200 body-fat measurements for a tester to considered an expert.
Thoughts: Make sure to get tested by the same person each time, otherwise, two people can get different results. Make sure they use high quality calipers (Lange, Harpinden). Minimum amount of sights I would suggest- 6 (can go as high as 12).
Hydo-static weighing: Called the "gold standard." Before DEXA (explained below), this was considered the best method to have your body-fat tested.
Pro: Very high validity.
Con: TOO many variables, reliability can be poor.
Thoughts: Can be difficult to find. Cost might be a little high.
DEXA (Dual Energy X-Ray Absorptiometry): Could be called the "platinum standard." All you do is lie down on a table and a scanner goes over you from head to toe under a minute.
Pro: EXTREMELY accurate. It measures and divides out lean mass to the point of the mineral content in bones. It's also great to see just how much intra-abdominal or organ fat you have (HIGH correlation to early death and CHD).
Thoughts: Can be difficult to find. Cost can be prohibitive (a couple hundred dollars).
Final thoughts-
Infra-red: If this is something you might use on a regular basis, same time of day, it MIGHT be OK to use as a tracker, BUT NOT for accuracy. The problem though, let's be honest, A LOT of us here are quite obsessive-compulsive and seeing higher levels than what might actually be could be psychologically hard on some of us.
If anything, I would get my body-fat tested via calipers, then, immediately have it tested via infra-red. Then, use THAT number from the infra-red as your guide to track your progress.
Bod-pod: If there are more trusted methods available I would go with those. I would choose this over infra-red. Just the lack of availability makes this a poor choice.
Calipers: My choice. Cost is cheap and if you get the same experienced technician it has high validity and reliability. You can usually find this at a local university. Some community colleges might have it but their equipment might not be the best. But, in all honesty, there are some high quality plastic calipers and even if they use a 3 point method, the result won't be that far off than a high quality caliper, 6-12 point test (maybe 1-2% difference?).
If anything else, it's also great to help you know where you need to train a bit more. No, I'm not talking spot reduction, but re-composition… say your thigh measurement was 10mm, so you begin developing and building more muscle in that area. Now with the increase in muscle mass, your measurement is 8mm.
One controversial area (but growing in support) of knowing your measurements has to do with hormone imbalances. It's beyond the scope of this conversation, but there is some growing thought about body-fat levels in different places of the body and how different hormone levels affect those placements (Hawkmoon put up a study about this not too long ago).
Hydro-static: Even though it's the gold standard, here's the thing that really hurts this test you probably don't know. The original studies that were used to test the accuracy of this method were CADAVERS. Not a big deal in that, but, the problem lies in how the test is done. You sit on a seat connected to a scale in a tank filled with water, exhale all your air, sink down, hold your breath and try to hold VERY still as the scale "normalizes" on a number (when you sink down, the scale arm tends to bounce around a little bit). You do this several times and then take the average.
Here is the cadaver part and how it doesn't crossover very well with a live human…
Cadaver- All the air can be exhaled from them, so they sink fully. The tester can wait for the scale to settle before taking the final number.
Humans- A) it's very hard to exhale all the air from your lungs (it's impossible) so you always have a "residual tidal-volume" left over (which they try to educationally guess/calculate how much that is for your size).
B) Also, it's easy to fool yourself you got all your air out (I remember testing an "ultra-A type" from the Chicago Northshore and she floated like a balloon. I kept challenging her that she wasn't exhaling all her air and she in turn was becoming quite frustrated with me demanding she was. Her results turned out horrible- her body-fat was high but I know nowhere near what her test results were). You pretty much have to exhale all the way to the point of your chest hurting and almost passing out, seriously.
C) You need a VERY good tester. As mentioned, the scale arm bounces a little. For a live human, the arm never really settles exactly, so there is a bit of guesstimating of what the final number is. Trying to hold your breath for that long AFTER you honestly exhaled every bit of air possible is HAAARRRRRRD! You come up GASPING for air... and again, you do that several times!
DEXA: The sad thing is the cost. Even just from a health perspective it would be great to know and track how much fat you have around your organs. But, using this as your preferred choice is just not practical.
