Man, Drawn to Scale
Tuesday, March 7, 2006
There's an enemy lurking in my bathroom, and it isn't mildew. That, I could ignore. It's my digital scale, and I'm addicted to it.
No day begins without an LED update on the battle of Deiner vs. gravity, no midnight passes without a final glance down to see what those M&Ms popped during "Lost" hath wrought. The scale is egg-shaped and made of glass, with metal plates for the pads of your feet. Four numbered buttons line the bottom, one for each family member who dares to have his weight recorded and saved. My wife won't go near the thing.
You know the story: Middle-age guy starts working out at the Y after avoiding the gym since high school. Burgeoning manboobs recede, corset-tight pants become baggy and the face loses some accrued puffiness. Then he buys an iPod, sneakers that cost more than $24.99 and . . . one of those electronic scales that records both weight and body fat.
I loathe those people, and, man, I'm really hating myself these days. The sneaks are great and I certainly don't miss the manboobs-in-the-making. But it's the digital doohickey -- the Health o Meter Professional Body Fat Monitoring Scale -- that has, oddly enough, affected my daily regimen the most.
Needing to replace the battered scale I'd been using, I found that upgrading from a merely cool scale to the ultimate body-fat nag cost only a few bucks more. (Well, $60 ain't cheap.) And the Target gift card from Mom didn't hurt.
So I got the scale, and I can't get enough of it -- even if it doesn't seem to do what it's supposed to. The scale uses bioelectric impedance analysis, or BIA, to measure body fat. (Theoretically, every time I hit the treadmill I'm nudging my body fat percentage lower by gaining muscle and increasing lean body mass.)
According to the literature that came with the device, "A harmless bioelectric current passes from the foot pads through the body. The current travels at different speeds through lean mass and body fat."
Using information you input -- age, height, sex -- and your weight, the scale's microprocessor then "analyzes the impedance, or speed, of the current," and deduces your fat-to-everything-else ratio.
Not so fast, says Cris Slentz, an exercise physiologist and senior research scientist at Duke University. Slentz, who's been studying exercise and body composition for nearly 30 years, said he recently reviewed the research concerning BIA and came up with a simple conclusion: Don't trust your scale.
"I don't believe that bioelectric impedance works well at all. My guess is that somewhere down the line it has some promise," he said, "but it hasn't reached that point yet."
He said BIA may be most effective in measuring the density of perfectly cylindrical solutions, like individual body parts, not lumpy middle-aged bags of flesh. So the best way to gauge someone's body fat using BIA would be in cylindrical chunks -- in other words, measure your arms, legs and torso separately, which, Slentz pointed out, "would be neither comfortable nor convenient."
That's good to know, because I've been following the ups and downs of my body fat percentage as if it were the stock market. I'm 42, 6-1 1/2 , and the percentage has ranged from as low as 22.5 to as high as 26.8. (Note to self: Skip the gravy at Thanksgiving next year.) That's generally in the "high" range, according to the scale literature. By comparison, a calculator on the Web site for the U.S. Centers for Disease Control pegs my body mass index (BMI) at 24.3, which is "normal" by its standards.
When I told Slentz I often see a swing of three or four percentage points in my body fat from sunup to bedtime, silence ensued. "Did it ever occur to you that it's highly unlikely you'd have a 3 percent change in body fat in one day?"
Health o Meter spokeswoman Jennifer Hansard wasn't surprised at all by the discrepancies, citing hydration as the culprit. "If your hydration level is lower in the morning, it's going to increase your body fat percentage," she said. The less water in my body, the longer it takes the electric pulse to zip through my body -- and the higher that digital blip at my toes.
"It's measuring your lower body," she said, "then extrapolating that number to give you an estimate."
Because the device has a margin of error of plus or minus 1 percentage point, she added, my actual body fat most likely falls somewhere in between the morning and evening tallies.
Whatever. It's still my favorite toy, whether I'm watching my body fat percentage bounce around like an errant love handle or testing how sensitive it is when determining my weight.
And sensitive it is. Can it tell the difference in pounds between my clothes being on or off? Of course. How about pre- and post-workout? With ease, and the difference is enough to keep me going back to the gym. Wet hair vs. dry? Remarkably, yes, by just a smidgen. Miss a meal and the number plunges; eat two Lean Pockets instead of one, and you'll know about it. There are also ickier ways the thing has proved its apparent accuracy when it comes to weight, most involving substances that are ultimately flushed.
That's why I keep it next to the toilet. ·