I was reading a story written by Zach Lewis, a Health page columnist for the Plain Dealer, on having his body fat measured. It seems that he had a fitness assessment that included a body fat assessment utilizing electrical impedance...a method that often provides questionable results. An inquisitive guy, he went on a hunt to find out exactly what his body fat was. He was tested hyrostatically (the underwater test and considered the gold standard of testing), with body fat calipers, was tape measured, placed in the Bod Pod which measures the amount of air the body displaces, and with a DEXA scanner (a piece of x-ray equipment normally used to 'scan' for bone density). He received measurements ranging from a high of 16.8% to a low of 7.3%. Quite a range...and terribly disconcerting. I knew his frustration with wondering what to think and sent him the following email:
Hi Zach,
I read your article on body fat assessments and share your frustrations. I am an Exercise Physiologist and a columnist for Ohio Sports and Fitness Magazine and have been conducting fitness tests since the 80’s using skinfold calipers and a six-site test. I have conducted about 10,000 tests during that time and consider myself skilled with calipers. I believe it to be the only reliably repeatable test in the field because the only room for error is in the hands of the tester. I don’t know how many sites were used in your assessment, but the more, the better.
I tell clients to remember this about body fat assessments. They should be done as part of a total fitness assessment and be used to form a baseline of information against which the value of an exercise program can be measured. “We’re doing this to compare you to yourself…not to other people,” I remind them. Human error in taking these measurements can be large, but are reduced if you have someone who has done many hundreds before, takes accurate notes of the sites, uses a multi-site test, and most importantly…is the same person for the retest.
I think you’re right about the ‘gold standard’ test, underwater weighing, but remember well the advice of the head of the Exercise Physiology program who taught me this technique during my academic years, “dunk them 10 times. The first five are useless as the subject is getting used to the completely foreign concept of going under water AFTER blowing all the air out of their lungs.” How right he was. I’m guessing you were dunked 2-3 times.
Affordability/convenience is the other issue. Clearly, some of the tests you mentioned are out of the price range of the common exercising man…and since their repeatability is questionable, I suppose that’s a good thing.
John Rolf.
I'm sure he'll appreciate my insight. Had he only come to me, I'd have given him an accurate reading, explained its function, and sent him home a happy man. Somehow though, in all he's experienced on Cleveland's health and fitness scene, he somehow managed to miss this extraordinary blog. Well...maybe not anymore.
Survival Workout Duration: 60 minutes
Heart rate during workout: 100-150 bpm.
Calories burned: 600
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