Body Fat

[OptikaNET]

Hi, my calipers arrived today. Just tried them out (averaging 4 readings - all of which read the same anyway). Got a fat-percentage value of 19.6. Used my Tanita balance and got a fat-percentage of 20.6. I'd say they were reading pretty closely the same and since the calipers cost £3.99 and a flimsy piece of plastic and the balance cost £500 and is a complex, calibrated piece of precision electronics, I'm inclined to believe the balance!

Interesting experiment though.

Kind Regards
Dave

[Deviation]

Well paying $500 certainly makes you more inclined to believe it. Besides 1% variance either way isn't a bad margin for error.

[OptikaNET]

That depends... when I worked with radioactive-labelled compounds in the lab, my error margin used to be 0.05%!!!

I would have found a 1% error margin horrendous!!!

Kind Regards
Dave

[Deviation]

That depends... when I worked with radioactive-labelled compounds in the lab, my error margin used to be 0.05%!!!

I would have found a 1% error margin horrendous!!!

Kind Regards
Dave

LOL. Well I didn't mean EVERYTHING.

[OptikaNET]

Learn to cultivate a sense of precision dear chap!

Kind Regards
Dave

[femaveeick]

One problem with BIA scales is that they don't handle people with thicker than average skin (which has more impedance). Or people who's thickness of skin varies often. Unfortunately I fall in that small group of people. I deal with psoriasis, which is an overactive immune response in the skin organ. I can't trust BIA even for trends of information. It's currently reading me at about 30% BF when just a month ago it read me at 25%--and I lost fat between now and then. I've even had the thing give me different answers when reattempting the measurement 3 times in a row.

At least with calipers, my trending is more accurate (for me).

[OptikaNET]

Hmmm... that's true. I often wonder if my skin has increased conductivity after a bath than at other times when it might be drier and whether that affects the reading or not, as well.

Still, it beats looking at your wobbly belly and saying to yourself; "Am I losing any fat at all?"

Kind Regards
Dave

[femaveeick]

Hmmm... that's true. I often wonder if my skin has increased conductivity after a bath than at other times when it might be drier and whether that affects the reading or not, as well.

Oh, that's absolutely the case. You'll also find that you retain more water at the end of the day than at the beginning. That means you will have the perplexing case where at the beginning of the day the BIA scale says you weigh less but have more fat; but at the end of the day you weigh more and have less fat. Water conducts electricity better, so it treats it as lean mass.

[OptikaNET]

That's why I always weigh myself when I get up in the morning; before I have eaten or drunk anything but AFTER I have been to the toilet...

Kind Regards
Dave

[John Rippon]

Ah - the inevitable debate about measuring, or perhaps more correctly - estimating total body fat.

Some facts:

1. Estimating total body fat to accuracies of better than 1% are complete bollocks.
2. All estimates based on various tape measurements, all calipers, most BIA methods (e.g. Tanita scales) do not take into account the whole body but make assumptions about what might be in the whole body based on - at worst a crude measurement of subcutaneous fat thickness as a single point; at best a rough estimate of body composition over the lower body (path taken by the current between the electrodes on a BIA scales). While some of these methods may give a reasonable estimate of the amount of fat over certain areas, they all rely on extrapolating from there to give an estimate of total body fat based on empirical formulas that have never really been subject to solid scientific verification. If you have lots of subcutaneous tummy fat, the assumption is that you must have proportionately lots of visceral fat throughout your body. Put an age adjustment in to take account of the notion that, if you are older, you will probably have proportionately even more visceral fat. Question: How do they come up with these empirical formulas for such an extrapolation? Answer: If you're lucky they might have done so by assuming that determination of overall body density by means of total immersion is 100% accurate, then taken lots of samples over a broad range of subjects (gender, ethnicity, 'body type', age, etc. etc.). Again the likelihood of that being the case is bollocks. These formulas makes gross approximations as to the proportions of various constituents of the body, and about the absolute densities of each of those constituents. As but one example, most people are aware that mineral bone density can vary considerably from one individual to another. etc. etc.
3. If you are still in any doubt about how body fat estimates made by different methods give inconsistent results: Personal example. I once had my BF estimated by three methods all within an hour of one another: Cheap plastic digital calipers (Jackson/Pollock 3-site measurement): 8%, Expensive Harpenden calipers (Jackson/Pollock 3-site measurement): 10%, Very expensive DEXA scan (whole body dual-energy X-ray analysis) 14+%.
4. There are likely only two reasons why you think you want a BF% number for yourself: a) You want to compare it against the figure you've read or hear for someone else. b) You want to have a set of numbers over time to content yourself that there is a trend in the direction that you desire. I hope I've dispelled the idea that reason a) is pointless. b) seems a more 'reasonable' reason, but given my next point, I hope you'll see that placing reliance on such a set of numbers is dicey unless the trend is quite apparent (in which case your camera, mirror, clothes and friends are probably a better guide than the set of numbers).
5. Apart from inconsistencies between different methods of estimating BF illustrated in 3) there is also the problem of inconsistencies between different measurements taken by the same method. With calipers the biggest variation is generally due to inexperience and/or poor technique on the part of the person taking the measurements. Other factors also have to be eliminated - such as different levels of hydration at the time of measurement, stance and degree of relaxation of the subject etc. If I were to hazard a guess as to what would be a fair error estimate for an experienced person estimating BF by calipers and following all the prescribed procedures for doing so, it would be nearer 1% for low body fat (e.g. < 10% men, < 15% women) or perhaps twice that much for people nearer the 20%+ range. These are only guesses, but quoting figures to 0.1% are meaningless. There are also some subjects for whom it is very difficult to separate their subcutaneous fat from the underlying tissue. For these people (I've come across a few) it's virtually impossible to take any meaningful measurement at some sites.

Bottom line as far as my advice is concerned is: Don't bother about BF% figures unless you are confident that the method you are using gives consistent results (and you need to prove this). Even if you do, don't even think about comparing your figures with those of someone else. Bodybuilders who say they are 3% BF better go and get a DEXA scan. The guy who took mine in Australia has dealt with hundreds of bodybuilders over several years and told me the lowest figure he got for a guy who was absolutely shredded was 8%.