Discussing the percentage of your body that's composed of fat seems unsavory, but here I am, baring it all, with an Oregon Scientific Personal
Fitness analyzer (PFA112; $100;
www.oregonscientific.com) clenched between my fingers. The device sends an electrical impulse through my body, measures the resistance from my flesh and bones (fat impedes more than muscle), and flashes the verdict: 17 percent. Excuse me? Twenty percent is normal and considered healthy, but when I was tested recently my fat content was less than 10
percent (not surprising, given my diet and eight hours of cycling a week). My occasional headlong dive into
a plate of nachos notwithstanding, the PFA was plain wrong. Body fat analyzers that measure electrical impedance can vary by 3 percentage points on the best days, more if your hydration level is low or temperature is high. But a distortion of 70 percent? If you really want to measure your body fat--without using the accurate but expensive methods found in clinics or hospitals--I suggest you use the PFA for motivation or
measuring progress, not for the gospel truth. As for me, when I want to hear insults about my body, I'll take my shirt off in front of my riding buddies--it's $100 cheaper.