So, I spend most of my time these days working in a Clinical Biochemistry Department. In the corner of an examination room sits this piece of equipment, which is used on all of the participants in the study I am working on, called the TANITA Body Composition Analyzer. It's most important function is that it measures % body fat. For those who haven't tried something similar, you stand on it barefoot and grip some metallic handles and then little electrical currents are sent through various areas of the body, the resistance is measured and % of various tissues determined. You have to enter your height and whether or not you are "athletic" and it weighs you and figures out the rest.
After I was done doing eye examinations the other night, I figured it was time to take my shoes off and give the TANITA a try. I'd never had my % body fat measured, so wasn't really sure what to expect.
Needless to say I was a bit shocked to see 10.9%. Seemed quite low, but I wasn't about to complain. I mean for those of you who have seen me in real life, you know I look like a pretty normal woman. I had always thought of 10% as the lowest a woman could possibly go before she actually turned into a man.
Anyway, the MOST remarkable thing about the printout I received and the reason I am actually writing this, is it told me the optimal measurement for me would be 27% (!). Is a woman my age with 27% body fat healthier than I am? The actual "healthy range" for women ages 20-39 is 21-33%. Of course the confounder is most of my fat is not fat, it is muscle (to be more precise, I have 5.75 kg of fat, 44.8 kg muscle and 2.4 kg of bone). So women who have a lot of muscle and little fat, but normal or close to normal BMI are still healthy. You didn't need SLG to point this out, though. So why is it that the WHO/NIH who made these guidelines can't figure it out? Well, it goes back to a large study done by Gallagher in 2000 in the American Journal of Clinical Medicine, where they converted the normal BMI range to normal % fat range. He admits that they basically had no subjects in the low normal or below normal BMI range (!), so they couldn't make reasonable caclulations there.
Readers, don't be fooled into thinking that % body fat below 21% is unhealthy. In fact, don't be falsely reassured if your % body fat is in the upper end up normal. It is not clear how exactly % body fat correlates with BMI or how % body fat correlates with longevity. But I have subsequently read that most competitive female runners/triathletes have a % body fat between 10-15.
Let's look at some pictures I found on leighpeele.com. Then you can probably figure out for yourself what's healthy and what's not.
First, woman? man? steroids? What IS hiding uder that bikini? And you can't tell me that I need to look like this to get to be a faster runner.
Now take a look at Miss 11% above. No, despite what you're thinking, that is not me. HA! Just kidding. How is it I have the same body fat percentage as her? Could the answer lie in les boobs (yes, that should be pronounced in French)? All I can say is thank God I don't look like that.
I actually think I look almost EXACTLY like miss 18% :). Right, SR?
Now, getting back to the WHO % body fat guidelines. Miss 25% and miss 30% are well within the "healthy" range according to the WHO, whereas Miss 18% (and even Miss 20%) is not.
Edit (thanks, Meghan Hicks): It is difficult to know which of these women is healthiest. But I think it is wrong that the WHO implies that women with less than 21% bodyfat are unhealthy and that women with 30% body fat are healthy based on a rough estimate from normal BMI to % body fat. I am also having difficulty finding how % body fat can be used as a determinant of health or as a determinent of fitness among elite athletes, when the measurement seems to be, at least to a certain extent, affected by breast size.
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