I am standing naked on a digital bathroom scale. Electrical currents are speeding through my body, skipping past water, bone, blood and muscle in search of fat.
Let's get personal--very personal: I'm 48, stand 6 feet 1, and according to my Tanita Body Fat Monitor/Scale, I weigh 184 1/2 pounds and have 19% body fat. That's 35 pounds of goo.
For a couple of weeks I've been testing two battery-powered body-fat measuring devices: the $65 Tanita scale and a competing $139 Omron hand-held fat analyzer.
Both devices claim to take accurate fat readings by relying on an arcane technique called bioelectrical impedance analysis. Water is the biggest ingredient in our bodies, followed by fat. Given that fat doesn't conduct electricity as well as water or muscle, these monitors calculate fat readings within seconds by tracking the body's resistance to a faint electrical current.
Frankly, I didn't think these gadgets would work--and I managed to trick them into giving some false readings. But the big surprise is these fat monitors turned out to be pretty accurate--the Tanita more often than the Omron.
To get an independent fat measurement, I went to Bodies in Motion in Santa Monica for a time-tested caliper fat test. My health club trainer Sean took plastic calipers and pinched my back, upper thigh and waist to measure the rolls of fat under my skin. He did the math and pronounced I had 19.8% body fat. (For my age and sex, the normal fat range is 17% to 23%.)
This caliper fat test was impressively close to the 19% reading generated by the Tanita scale. By comparison, the Omron HBF-300 Body Fat Analyzer generally calculated my body fat at 22%.
Sean, whose taut body holds 12% fat, noted that some marathoners carry only 6%. I'm middle-aged, so those figures seem ridiculously out of reach. But he advised me to lift more weights and hit the treadmill to convert more fat into muscle.
If I wanted a more accurate fat test, my next step would have been to dunk myself in a pool. Some folks insist on a hydrodensitometry reading because it offers the most precise fat measurements. But this also requires your being submerged in a pool, while a clinician repeatedly measures how much of your fat is displaced by water. Some health clubs offer the water/fat test for $45, but I skipped it.
How important is it to track body fat? If you are overweight--and about half of American adults are--going on a crash diet will shed pounds but not necessarily fat. A study by the U.S. Department of Agriculture showed that almost any diet that limits calories to 1,500 a day will cause weight loss. Unfortunately, most who lose weight in a hurry eventually gain it back. One problem is that few diets have long-term value unless their regimen cuts back on fat intake and pushes complex carbohydrates, vegetables, fruit and exercise.
So having a fat measurement tool at home might shame you into thinning down. I took a liking to these fat monitors. They were easy to use, and I found comfort knowing my fat level was in the normal range.
Of the two devices, the clear winner is Tanita: It's cheaper, more accurate and also measures weight. By contrast, the Omron device is not a weight scale; it measures only fat. So each time I had to type in my weight before the Omron could figure out my fat--which was a nuisance. Granted, the Omron monitor is portable--it weighed only a pound--and measured fat when I was fully clothed. But the Omron was quirky--my fat readings varied, sometimes from minute to minute, and the figures were a few percentage points higher than on the Tanita scale or my caliper test.
The Tanita fat monitor was easy to set up. The package came with four AA batteries, and it took only a minute to program in my sex and height. The scale's surface has four metal plates, where I placed the balls and heels of my feet so the electrical current could connect. I also had to stay barefoot; otherwise I'd get a total weight reading but no fat numbers.
I tapped a button to start the device, then stepped on. My weight popped up instantly, followed by a flashing 5,4,3,2,1 and whammo, the digital screen read 19% (body fat).
There is a method to taking proper measurements. Tanita's instruction booklet urged me to weigh in the same time each day, preferably at night, because in the morning we tend to be dehydrated, which alters readings, as does caffeine or alcohol.
I wasn't very disciplined, though, and I took measurements at all hours. I particularly enjoyed weighing in after gobbling a double double cheeseburger from In-N-Out Burger, only to see no change in my fat numbers. Over two weeks there was no more than a 1-point shift in my fat.
At first I didn't trust these numbers, so I tried to trick the Tanita scale. I hoisted my son, Jann, who weighs 85 pounds, and stepped onto the scale; my fat shot up to 37%. I also stepped on carrying barbells, bottles of water and our cat; all bounced up my weight and inflated my fat readings.