body fat testing accuracy?
03-02-2007 03:35 PM
body fat testing accuracy?
Ok, I did a 7-point test myself and came up with 12.5% bf. Now, I wasn't so sure of how correct I was doing the procedure, so I found a local place that does hydrostatic (underwater) bf testing. Great, from what I read this is suppose to be dead on accurate. Well, I am more confused then ever now, let me explain.
I started to carb down at the beginning of this week at 188lbs with that 7-point measurement. Here is a picture of what I look like: (Seems like 12-13% to me)
Now, in 5 days I dropped 8 lbs and I am down to 180 which I contribute to loss of glycogen, no big deal. So today (6th day on carbing down), I went to get my BF% tested with the hydrostatic method. This is what they got:
Height: 69.25 "
Ankle Circumference: 8.75
Water Temp: 32 C
Resting Pulse: 60
Water Weight: 8500 grams
Now the results:
Body fat: 7.1%
Lean body Mass: 167.1 lbs
Fat Body Mass: 12.7
Now, I'm shocked by this because no way do I think I look like 7%! Now i told the tester how I started this diet and i was 188 in the beginning of the week. So he used 188 for weight instead and still got 8.8%!! Now, here are the questions:
Is there any way this test could be way off?
Could 6 days of carbing down really skew actual results?
If I am glycogen drained, would that really make a 1.5% difference?
If I am around 8%, why do I not have a 6 pack?
I hope someone might know the answers to some of this, but from what I read, hydrostatic testing is suppose to be pretty accurate.
03-02-2007 03:38 PM
Don't get me wrong, you're in better shape than the average guy but you don't look 7%. Seven % is Mens Fitness cover model. I'm thinking they screwed-up your test.
03-02-2007 03:48 PM
No problem man, I agree with you. I am trying to figure out if they did screw up, where it could of went wrong? You would think they do this all the time and it would be pretty accurate. Could they of possibly just messed mine up? Would you even think I am at 8.8?
03-02-2007 03:55 PM
I'm no expert on this by any means. There are a number of people on this board who are certified trainers of one sort or another. I'll let them chime in.
Originally Posted by peterson24
For what it's worth, you look pretty similar to myself and my Tanita scale consistently pegs me at 14-15% bf.
03-02-2007 04:44 PM
Pop-Lock champion of 84'
Of course everybody is different but 10% Or under is easily visibile abs - You look around 11.333345%
03-02-2007 04:47 PM
On a Mission!
Your no where near the single digit BF reading the water test put you at. Your not in bad shape, not at all, but your not any where near the single digits. I would go back in and demand a refund if they charged you. I would also demand they retest you free of charge. At a glance I would put you around 13%-15%; which is still a decent BF. How old are you? I believe for men anything under 20% is considered normal range, and for women it is 24%. I can't remember exactly. Personally, I feel these ranges should be lowered.
The lowest I've ever been is 9% ... taking that into account and speaking from past experience I would say you would be able to clearly see muscle separation and definition any where < 12%; even when soft/not flexing. For me (at 9%) I had some pretty mean veins running up my waist line. Oblique were very visible as well. Striations could also be visible in certain muscles.
Just my .02 cents,
03-02-2007 04:56 PM
I emailed for a retest. I knew the numbers were rediculous, I just wanted verification. We'll see what happens with this. But I still say I am at 12-13%. If flexing, abs are visible no problem. that picture is relaxed
03-02-2007 05:33 PM
bottom line bad test...... hydrostatic bodyfat measurements require all oxygen to be expelled from lungs while underwater. Most find this difficult because of the drowning sensation. The most accurate ways to determine bodyfat percentage are DEXA (Dual energy X-ray absorptiometry) and the most accurate of all the bodpod, but good luck finding one. The only one I know of in my area is at The University of Virginia Tech.
Anyone with experience with calipers will be able to give you a fairly accurate reading (within %3 maximal for a good tester). Measuring yourself will not work well, I suggest you find an experienced exercise physiologists and get measured. Any local colleges should have some type of exercise science programs and the students always need people to practice on and usually the professor will double check to make sure it is an accurate reading.
03-02-2007 05:39 PM
From my understanding, caliper tests are very bad at measuring your actual bf%, but (when tested using the same tester each time) can be pretty effective in measuring changes in bf%.
03-03-2007 01:17 AM
I beg to differ about the bodpod being the most accurate. They had one in my gym recently, and it wasn't nearly as impressive nor consistent as DEXA. The lame thing about Bodpod is that they bash every other method in their promo literature, and at the same time, their method takes into account height, weight, age, race, sex. Basically it factors in a ton of assumptions that can potentially widen the margin of error. If you have any hard data showing better accuracy with bodpod versus DEXA, I'd like to see it. Bodpod lasted only a few days at my gym, becauser apparently no one bought in.
Originally Posted by blackcj7
The only accurate ways to measure bodyfat boil down to 2 methods:
-- Put the person in a blender, pour in a giant skimmer.
The best judges of bodyfat are the mirror + pictures (or video). And calipers by an experienced technician to measure change, if you MUST have a numerical gauge.
03-03-2007 06:55 PM
Journal of Applied Physiology
Vol. 89, Issue 2, 613-620, August 2000
Body composition techniques and the four-compartment model in children
David A. Fields and Michael I. Goran
Division of Physiology and Metabolism, Department of Nutrition Sciences, and The Clinical Nutrition Research Unit, University of Alabama at Birmingham, Birmingham, Alabama 35294
The purpose of this study was to compare the accuracy, precision, and bias of fat mass (FM) as assessed by dual-energy X-ray absorptiometry (DXA), hydrostatic weighing (HW), air-displacement plethysmography (PM) using the BOD POD body composition system and total body water (TBW) against the four-compartment (4C) model in 25 children (11.4 ± 1.4 yr). The regression between FM by the 4C model and by DXA deviated significantly from the line of identity (FM by 4C model = 0.84 × FM by DXA + 0.95 kg; R2 = 0.95), as did the regression between FM by 4C model and by TBW (FM by 4C model = 0.85 × FM by TBW 0.89 kg; R2 = 0.98). The regression between FM by the 4C model and by HW did not significantly deviate from the line of identity (FM by 4C model = 1.09 × FM by HW + 0.94 kg; R2 = 0.95) and neither did the regression between FM by 4C (using density assessed by PM) and by PM (FM by 4C model = 1.03 × FM by PM + 0.88; R2 = 0.97). DXA, HW, and TBW all showed a bias in the estimate of FM, but there was no bias for PM. In conclusion, PM was the only technique that could accurately, precisely, and without bias estimate FM in 9- to 14-yr-old children.
03-03-2007 08:29 PM
NIMBUS NUTRITION Co Founder
I'd say your about 12% in that picture...
Originally Posted by peterson24
The best way to test your body fat is to get a trainer, preferably one that knows what they are doing, to do a 4 point caliper test on you, 4 times in a row back to back....we call it the "4X4 method". You then take the average of those four tests as your actual Body fat.
Will this be accurate and as precise as possible?...No.
Is it effective?....Yes.
Go back to the same trainer, using the same calipers, every week and have him/her perform the 4X4 method. This will allow you to see if your making any progress. Be sure you have it done under similar circumstances every time. It should be pre-workout, at least 2 hours after your last meal ideally.
Hope this helps
03-03-2007 09:39 PM
Exactly your looking more around 12-13%. I'm a trainer so I read bf almost everyday. WHat I tell everyone is exactly what they said above. It's a good way to gauge your progress and it allows me to get a good idea of where the weight is going or coming from depending on the goals. The mirror is the best indicator don't let yourself get caught up in the numbers game.
03-05-2007 12:25 PM
I'll agree that an autopsy is the most accurate way of testing. I've personally hydrostatically tested thousands of people and really need experience to get accurate and repeatable results. Read the comparative methods document on wwwbodyfattest.com it compares all the methods. Also accurate formulas need to be used for determining BF with underwater weighing. Some places don’t have them. If they are measuring your ankle, their formula is flawed. Also, if they are using an analog scale suspended to the ceiling it's not going to be accurate. Find a place that uses load cells and a digital readout. Height is used to determine your residual lung volume. It you know what this is they should be able to override this value. BFT uses formulas developed by John Hopkins University. DEXA is not as accurate as many people think. It's a 2 dimensional look at your body and it also requires a doc's referral to be legally done. I've seen all methods be horribly inaccurate including hydrostatic but hydrostatic will most accurately track results. You can't argue with overall body density changes seen with hydrostatic. Bottom line: you didn't change this much this quickly. I’d have a hard time believing you changed even 1-2% in this short of time. No one can tell what % you are by looking at you, but in my experience you don’t look like 7%. Chances are you have one or more of the following contributing errors: poor equipment and/or operator, operator or equipment mistakes, or you didn’t get all your air out the first test. When you are 10% or lower every little bubble can make a difference.
03-06-2007 04:03 PM
Newer research challenges the idea that air displacement (bod pod) is superior to other methods. DEXA is still considered the standard for comparison of other methods. Further, as you'll see in the last abstract to follow, air displacement can be confounded by hydration, which it tends to falsely detect as fat mass:
Originally Posted by blackcj7
Obes Res. 2005 May;13(5):845-54.
Comparison of methods to assess body composition changes during a period of weight loss.Frisard MI, Greenway FL, Delany JP.
Pennington Biomedical Research Center, Baton Rouge, LA 70810, USA.
OBJECTIVE: To assess the accuracy of body composition measurements by air displacement plethysmography and bioelectrical impedance analysis (BIA) compared with DXA during weight loss. RESEARCH METHODS AND PROCEDURES: Fifty-six healthy but overweight participants, 34 women and 22 men (age, 52 +/- 8.6 years; weight, 92.2 +/- 11.6 kg; BMI, 33.3 +/- 2.9 kg/m(2)) were studied in an outpatient setting before and after 6 months of weight loss (weight loss, 5.6 +/- 5.5 kg). Subjects were excluded if they had initiated a new drug therapy within 30 days of randomization, were in a weight loss program, or took a weight loss drug within 90 days of randomization. Subjects were randomly assigned either to a self-help program, consisting of two 20-minute sessions with a nutritionist and provision of printed materials and other self-help resources, or to attendance at meetings of a commercial program (Weight Watchers). Body composition was examined by each of the methods before and after weight loss. RESULTS: BIA (42.4 +/- 5.8%) underestimated percentage fat, whereas the BodPod (Siri = 51.7 +/- 6.9%; Brozek = 48.5 +/- 6.5%) overestimated percentage fat compared with DXA (46.1 +/- 7.9%) before weight loss. Correlation coefficients for detecting changes in body composition between DXA and the other methods were relatively high, with Brozek Deltafat mass (FM; r(2) = 0.63), Siri FM (r(2) = 0.65), tetrapolar BIA percentage fat (r(2) = 0.57), and Tanita FM (r(2) = 0.61) being the highest. DISCUSSION: In conclusion, all of the methods were relatively accurate for assessing body composition compared with DXA, although there were biases. Furthermore, each of the methods was sensitive enough to detect changes with weight loss.
Comparison of Methods to Assess Body Composition Changes during a Period of Weight Loss -- Frisard et al. 13 (5): 845 -- Obesity
Obes Res. 2005 Jan;13(1):75-85. Links
Percentage fat in overweight and obese children: comparison of DXA and air displacement plethysmography.Radley D, Gately PJ, Cooke CB, Carroll S, Oldroyd B, Truscott JG.
Leeds Metropolitan University, School of Leisure and Sports Studies, Beckett Park Campus, Fairfax Hall, Leeds LS6 3QS, UK. email@example.com
OBJECTIVE: To compare percentage body fat (percentage fat) estimates from DXA and air displacement plethysmography (ADP) in overweight and obese children. RESEARCH METHODS AND PROCEDURES: Sixty-nine children (49 boys and 20 girls) 14.0+/-1.65 years of age, with a BMI of 31.3+/-5.6 kg/m2 and a percentage fat (DXA) of 42.5+/-8.4%, participated in the study. ADP body fat content was estimated from body density (Db) using equations devised by Siri (ADP(Siri)) and Lohman (ADP(Loh)). RESULTS: ADP estimates of percentage fat were highly correlated with those of DXA in both male and female subjects (r=0.90 to 0.93, all p<0.001; standard error of estimate=2.50% to 3.39%). Compared with DXA estimates, ADP(Siri) and ADP(Loh) produced significantly (p<0.01) lower estimates of mean body fat content in boys (-2.85% and -4.64%, respectively) and girls (-2.95% and -5.15%, respectively). Agreement between ADP and DXA methods was further examined using the total error and methods of Bland and Altman. Total error ranged from 4.46% to 6.38% in both male and female subjects. The 95% limits of agreement were relatively similar for all percentage fat estimates, ranging from +/-6.73% to +/-7.94%. DISCUSSION: In this study, conversion of Db using the Siri equation led to mean percentage fat estimates that agreed better with those determined by DXA compared with the Lohman equations. However, relatively high limits of agreement using either equation resulted in percentage fat estimates that were not interchangeable with percentage fat determined by DXA.
Percentage Fat in Overweight and Obese Children: Comparison of DXA and Air Displacement Plethysmography -- Radley et al. 13 (1): 75 -- Obesity
Am J Clin Nutr. 2004 Jul;80(1):64-9. Links
Comparison of methods to assess change in children's body composition.Elberg J, McDuffie JR, Sebring NG, Salaita C, Keil M, Robotham D, Reynolds JC, Yanovski JA.
Unit on Growth and Obesity, Developmental Endocrinology Branch, National Institute of Child Health and Human Development, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892, USA.
BACKGROUND: Little is known about how simpler and more available methods to measure change in body fatness compare with criterion methods such as dual-energy X-ray absorptiometry (DXA) in children. OBJECTIVE: Our objective was to determine the ability of air-displacement plethysmography (ADP) and formulas based on triceps skinfold thickness (TSF) and bioelectrical impedance analysis (BIA) to estimate changes in body fat over time in children. DESIGN: Eighty-six nonoverweight and overweight boys (n = 34) and girls (n = 52) with an average age of 11.0 +/- 2.4 y underwent ADP, TSF measurement, BIA, and DXA to estimate body fatness at baseline and 1 +/- 0.3 y later. Recent equations were used to estimate percentage body fat by TSF measurement (Dezenberg equation) and by BIA (Suprasongsin and Lewy equations). Percentage body fat estimates by ADP, TSF measurement, and BIA were compared with those by DXA. RESULTS: All methods were highly correlated with DXA (P < 0.001). No mean bias for estimates of percentage body fat change was found for ADP (Siri equation) compared with DXA for all subjects examined together, and agreement between body fat estimation by ADP and DXA did not vary with race or sex. Magnitude bias was present for ADP relative to DXA (P < 0.01). Estimates of change in percentage body fat were systematically overestimated by BIA equations (1.37 +/- 6.98%; P < 0.001). TSF accounted for only 13% of the variance in percentage body fat change. CONCLUSION: Compared with DXA, there appears to be no noninvasive and simple method to measure changes in children's percentage body fat accurately and precisely, but ADP performed better than did TSF or BIA. ADP could prove useful for measuring changes in adiposity in children.
Comparison of methods to assess change in children's body composition -- Elberg et al. 80 (1): 64 -- American Journal of Clinical Nutrition
Eur J Clin Nutr. 2003 Nov;57(11):1402-10. Links
Estimates of percentage body fat in young adolescents: a comparison of dual-energy X-ray absorptiometry and air displacement plethysmography.Radley D, Gately PJ, Cooke CB, Carroll S, Oldroyd B, Truscott JG.
School of Leisure and Sport, Leeds Metropolitan University, Leeds, UK. firstname.lastname@example.org
OBJECTIVE: To evaluate the accuracy of percentage body fat (%fat) estimates from air displacement plethysmography (ADP) against an increasingly recognised criterion method, dual-energy X-ray absorptiometry (DXA), in young adolescents. DESIGN: Cross-sectional evaluation. SETTING: Leeds General Infirmary, Centre for Bone and Body Composition Research, Leeds, UK. SUBJECTS: In all, 28 adolescents (12 males and 16 females), age (mean+/-s.d.) 14.9+/-0.5 y, body mass index 21.2+/-2.9 kg/m(2) and body fat (DXA) 24.2+/-10.2% were assessed. RESULTS: ADP estimates of %fat were highly correlated with those of DXA in both male and female subjects (r=0.84-0.95, all P<0.001; s.e.e.=3.42-3.89%). Mean %fat estimated by ADP using the Siri (1961) equation (ADP(Siri)) produced a nonsignificant overestimation in males (0.67%), and a nonsignificant underestimation in females (1.26%). Mean %fat estimated by ADP using the Lohman (1986) equations (ADP(Loh)) produced a nonsignificant underestimation in males (0.90%) and a significant underestimation in females (3.29%; P<0.01). Agreement between ADP and DXA methods was examined using the total error (TE) and methods of Bland and Altman (1986). Males produced a smaller TE (ADP(Siri) 3.28%; ADP(Loh) 3.49%) than females (ADP(Siri) 3.81%; ADP(Loh) 4.98%). The 95% limits of agreement were relatively similar for all %fat estimates, ranging from +/-6.57 to +/-7.58%. Residual plot analyses, of the individual differences between ADP and DXA, revealed a significant bias associated with increased %fat (DXA), only in girls (P<0.01). CONCLUSIONS: We conclude that ADP, at present, has unacceptably high limits of agreement compared to a criterion DXA measure. The ease of use, suitability for various populations and cost of ADP warrant further investigation of this method to establish biological variables that may influence the validity of body fat estimates.
Obesity (Silver Spring). 2007 Jan;15(1):78-84. Related Articles, Links
Body composition of obese subjects by air displacement plethysmography: The influence of hydration.
Le Carvennec M, ***our C, Adenis-Lamarre E, Perlemoine C, Gin H, Rigalleau V.
Nutrition-Diabetologie, USN, Hopital Haut-Leveque, Avenue de Magellan, 33600 Pessac, France.
OBJECTIVE: We investigated whether air displacement plethysmography (ADP) could detect small changes in body composition of obese subjects with alterations in hydration. RESEARCH METHODS AND PROCEDURES: Ten obese subjects (mean BMI, 39.3 +/- 2.8 kg/m2) entered the ADP chamber without and with oil (1, 2, or 4 liters), water (1, 2, or 4 liters), or mixed (1 liter oil + 1 liter water or 2 liters oil + 2 liters water) loads. Real and measured changes in body composition were compared by regression analysis and Bland-Altman procedures. RESULTS: The ADP-measured changes in volume did not differ from the real values and were strongly correlated with them (r = 0.98). In all cases, loads of differing composition and similar volume led to different values of fat, fat-free mass, and percentage fat. Water was detected as increased fat-free mass only with loads of > or =2 liters, most of the water being falsely detected as increased fat mass. The observed changes were correlated with the real ones for fat mass (r = 0.68; p < 0.0001), fat-free mass (r = 0.66; p < 0.0001), and percentage fat (r = 0.61; p < 0.0001), but fat mass changes were overestimated by approximately 1 kg, and fat-free mass changes were underestimated by approximately 1 kg. This underestimation increased with the highest water loads, as shown by the Bland-Altman plot (r = -0.27; p < 0.05). Percentage fat changes were overestimated by 0.8% (p < 0.001); the magnitude of the error was correlated with the weight of the water load (r = 0.62; p < 0.0001). DISCUSSION: ADP accurately measures changes in body volume, discriminating small changes in body composition. It overestimates changes in adiposity, as most of the increased hydration is detected as an enlarged fat mass.
04-06-2007 01:52 PM
Well, I figured I post an update here. I started a diet plan 6 weeks ago for my summer prep and here is a pic of where I am currently. I'm thinking I may be around 9%.
04-08-2007 08:31 PM
NIMBUS NUTRITION Co Founder
Looking great peterson! You made some amazing progress...congrats!
Originally Posted by peterson24
04-10-2007 11:21 AM
Originally Posted by workin2005
Totally agree with Workin - good work!
04-11-2007 11:29 PM
Um... what did your 6 week cutting plan look like? diet + w/o
Originally Posted by peterson24
04-12-2007 12:08 AM
Running with the Big Boys
Definitely in the single digits or right on the cusp (depending on how your body stores fat). I didn't see this thread until now, but I am very surprised about the hydrostatic reading because it is the most accurate measurement of BF. The 7-point is also a good method to use to gauge your progress. Just make sure to take the reading under the same conditions each time for accuracy.
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