DEXA test for body fat percentage

RE: DEXA test for body fat percentage

aztimm — Tue, 21 Apr 2009 12:37:19 GMT

I'm curious to hear how the DEXA results compare to other body fat measurement results (eg: a bathroom scale w/ bodyfat readings). I'm also interested in this. It would be nice if someone who had the DEXA done also had a bathroom scale that measures body fat, just for a rough comparison. I have the Tanita scale. I weight myself a few times a week, but look more for trending over time rather than individual results. Immediately after a long run, I could weigh 8-10 lbs less than before it...but my body fat % may be higher. Seems like the more water I drink the higher the body fat %, unless something else is at work.

RE: DEXA test for body fat percentage

jim thornton — Mon, 20 Apr 2009 12:52:25 GMT

It was a guess, I guess.

RE: DEXA test for body fat percentage

Former Member — Mon, 20 Apr 2009 06:18:54 GMT

I'm curious to hear how the DEXA results compare to other body fat measurement results (eg: a bathroom scale w/ bodyfat readings). How would the most recent meal figure in -- like, a triple greezycheezyburger that hasn't been digested yet ? Or do you fast before the test ?

RE: DEXA test for body fat percentage

jim thornton — Mon, 20 Apr 2009 03:58:57 GMT

As I recall, it divides your body up into fat and lean mass. So, for a 150 lb. person who is 20 percent fat, that's 30 lb. of fat, and 120 lb. of lean (unless bones goes into another category, can't recall for sure.) Anyhow, say your greasy double bacon cheeseburger weighs 2 lb., which I doubt it does. Factor in that at least half of this is water. Then you are left with 1 lb., some of which is fat, some of which is protein, some of which is carbs. Even if the remainder were entirely fat, and it biased your DEXA scan to read you had 31 lb. of fat instead of 30, this is going to make a relatively insignificant addition ('t think you need to fast.

RE: DEXA test for body fat percentage

Former Member — Sun, 19 Apr 2009 15:25:34 GMT

Wrong. I'm right-handed.

RE: DEXA test for body fat percentage

Former Member — Sun, 19 Apr 2009 14:06:25 GMT

“I need you to lie down here,” Michelle says, indicating a sliding gurney beneath a movable QDR 4500 Hologic scanner arm. For the next three minutes, the arm glides back and forth, spraying my body with a piddling 5 microsieverts of radiation (the same amount we get each day just living on earth.) The DEXA emits very little radiation. The comparisons that I found are that it is roughly equivalent to 20 minutes of sun exposure, or to the amount of radiation we absorb on an airline flight from New York to California. The printout proves better than I could have hoped for. I’m down to 17.1 percent total body fat, which Hall says is distributed in a healthy, symmetrical way. My leanest parts are my legs—the left one at 14.2 percent fat, and the right one at 13.6. My abdomen, at 18.7 percent fat, is in no way suggestive of abdominal obesity, Hall says. To my surprise, my gut is not even my fattest body part. My head, at 20.1 percent, takes this dubious honor. I found this part of the results amusing, too (as did the hubby). Who knew that our heads contained so much fat? We were wondering whether brain matter counts as fat or as "lean tissue". Here are my numbers: Left arm ........ 23.6% fat Right arm ....... 25.7% fat Trunk ............ 14.9% fat Left leg .......... 29.8% fat Right leg ........ 31.3% fat Head ............. 19.4% fat Total body ...... 22.0% body fat

RE: DEXA test for body fat percentage

Former Member — Sun, 19 Apr 2009 12:54:30 GMT

To be expose at X-ray ( even ultra weak, but 15-20 mins is a very long time btw) for no medical reason is simply a dumb action at least. Safe maybe for 1 time every other year or so, but no way safe for monthly scan for attest body-fat %. X-ray are lethal period. Short weak exposure are "safe" only because it don't poise immediate harm and it can be the only way to uncover healthy issue, so the risk/benefit is reasonable, but nodoby recommend to take x-ray without any medical reason.

RE: DEXA test for body fat percentage

jim thornton — Sun, 19 Apr 2009 11:57:23 GMT

Three years and 20 lb. ago, I underwent a DEXA scan for an article on metabolism. Even though my weight was down then, I was a little afraid I would prove to be one of those generally skinny guys with enormous guts that have been increasingly classified of late as "weight normal, metabolically obese." Here, for your possible amusement and/or scientific interest, is my memory of the DEXA experience: Michelle H., an attractive 26-year-old scan technician at PBRC, tells me to take off my clothes and change into a zipperless gown. I’ve just gotten sprung from the metabolic chamber, and Tuong Nguyen has arranged for me to bivouac with Michelle in the DEXA lab while he compiles my metabolic results. At Michelle’s instructions, I feel a spike arise somewhere deep in my metabolic physiology. “I used to be almost a quarter pure lard,” I say, emerging from the changing room in the gown, which may or may not be on backwards. “You think I’m any less now?” “Hard to tell just from looking at you,” she replies with a North Carolina drawl. “We’ll know more soon.” As she leads me over to a digital scale, Michelle explains that DEXA (dual-energy x-ray absorptiometry) was originally pioneered to diagnose osteoporosis in women. In recent years, it’s also emerged as the single most accurate way to determine body composition, supplanting the old “gold standard”—underwater weighing—at many obesity research centers. Researchers even have a diagnosis for when otherwise skinny guys put on too much abdominal fat: "weight normal, metabolically obese." I hadn't reached this point--yet--but I worried it could one day prove my fate. “Okay,” Michelle says, pointing to a digital scale. “Step up.” Red numerals on the digital scale flicker around nervously before finally settling on 75.0 kilograms. “Now we get to subtract the gown,” she says. A few calculations later, and I get the Americanized results: 164.4 pounds, essentially identical to my college “fighting weight.” When Michelle next measures my height with a digital measuring stick, I brace myself for the likelihood of significant shrinkage. But once again the news is good: 6’ .76”—less than a quarter inch off my lifetime record. Maybe the tag team of life and gravity haven’t beaten me down quite so much as I thought. My body mass index, or BMI, is 22.0—safely in the “not too fat, not too thin” zone. Now, however, comes the real money shot: the DEXA scan itself. True, I’ve cut 20 pounds in the five years since the underwater weighing, but the question remains what kind of pounds have I shed? If my body has simply cannabilized its skeletal muscle for fuel, something not uncommon in cases of significant weight loss, I may have only turned myself into a skinnier, weaker, slower-metabolic version of the fat guy I used to be. “I need you to lie down here,” Michelle says, indicating a sliding gurney beneath a movable QDR 4500 Hologic scanner arm. For the next three minutes, the arm glides back and forth, spraying my body with a piddling 5 microsieverts of radiation (the same amount we get each day just living on earth.) Once the scan is completed, I get dressed and go to look over Hall’s shoulder. She’s using a computer mouse to draw red boxes around my arms, legs, trunk, spine, and head. A grayish halo surrounds my bones. “That’s your skeletal muscle,” she says, adding that the even finer layer on the perimeter is fat. “Maybe my eyes are getting worse with age,” I say, “but I can’t see much fat.” “You really don’t have much at all,” she replies, smiling. “The software will let us know exactly how much.” The printout proves better than I could have hoped for. I’m down to 17.1 percent total body fat, which Hall says is distributed in a healthy, symmetrical way. My leanest parts are my legs—the left one at 14.2 percent fat, and the right one at 13.6. My abdomen, at 18.7 percent fat, is in no way suggestive of abdominal obesity, Hall says. To my surprise, my gut is not even my fattest body part. My head, at 20.1 percent, takes this dubious honor. I wonder if researchers have a diagnosis for this, too: “weight normal, fat head.”

RE: DEXA test for body fat percentage

jim thornton — Sun, 19 Apr 2009 10:38:42 GMT

I found this part of the results amusing, too (as did the hubby). Who knew that our heads contained so much fat? We were wondering whether brain matter counts as fat or as "lean tissue". Here are my numbers: Left arm ........ 23.6% fat Right arm ....... 25.7% fat Trunk ............ 14.9% fat Left leg .......... 29.8% fat Right leg ........ 31.3% fat Head ............. 19.4% fat Total body ...... 22.0% body fat I am pretty sure brain is fairly fatty, at least the myelinated fibers. So, I just Googled this AFTER posting my supposition and.... The myelin insulation around neural axons and glial cells, which is mostly lipid, brings the fat content of an animal brain to about 60%. wiki.answers.com/.../What_percentage_of_the_brain_is_fat Your right arm and leg seem to be fatter than your left arm and leg. I remember a lack of symmetry for me, as well, but I can't remember if it was consistent with arm and leg. I am trying to guess if this means you are right or left handed. Righties tend to have somewhat bigger right arms, I would think, but you might also imagine that these bigger limbs get exercised more than their submissive limb mates, hence they would have less fat. It could go either way. But...extrapolating from my less fat leg (the right one), and the fact that I am right handed, I am going to guess that you are a lefty. Let me know if I guessed right! If I did, it wasn't a guess but rather a Holmsian deduction. Elementary, I must say. If I guess wrong, it was a guess.

RE: DEXA test for body fat percentage

Animal — Sun, 19 Apr 2009 10:20:33 GMT

I have tried to get in a number of study's at our local med school, which I work at, but am told I am too active to be part of the studies. What I do know is that the DEXA is the new gold standard for measuring body fat. There is a machine called the Peapod for babies under, I believe 8 kilos. The University of Colorado Denver is begin to use this machine for studies on babies. But, the Institutional Review Board, is making the investigators show the real need for the DEXA or Peapod on these small children, even if it is less radiation then to live a day or so in the Mile High city. I think for myself I would be happy to be in a study that would measure my body fat, but not more than once a year.:applaud:

RE: DEXA test for body fat percentage

KEWebb18 — Sun, 19 Apr 2009 08:58:51 GMT

It is nice to see that we don't have to go through the underwater weighing procedure! That was the old "gold standard". I remember having to go through that process in college. What most people don't know is the scales that measure body fat as well as weight depend highly upon your hydration status when you step on the scale. I wish that there was more emphasis on obtaining a healthy body fat percentage instead of reaching a goal weight is a much more attainable and healthy way to live.