Should You Trust That Body Fat Test?

Video

The Many Methods of Measuring Body Fat

MisFits columnist Howard Schneider takes his turn in a hydrostatic "dunk tank" test and various Post staff members try their hand at a hand-held device used in measuring body fat.

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"The only true way to measure body fat is through an autopsy," said Herb Conroy, group marketing manager for Homedics, one of several companies that sell body fat monitors. (Thanks, but I'll pass for now.)

The dunk tank put me at just under 21 percent, a bit higher than it should be, while the pinch test registered 18 percent, comfortably within the recommended range.

So should I panic, or have a beer?

That's the kind of anxiety this test can prompt. Company representatives seem to understand as much and are generally careful to say that their machines should be used more to establish trends than for precise measurements.

The devices, in other words, will give you a rough sense of where you stand but are better used to see whether your body fat percentage is going up, down or staying steady over time. If you're losing weight, for example, and you're body fat is creeping higher, that's a sign of unhealthy dieting -- weight loss through dehydration or the destruction of muscle tissue. By contrast, if you're body fat readings are going down but the scales are not budging, that's a sign that you're building muscle and getting stronger.

"What we try to tell everybody is: Don't get hung up on 'Am I really 20 percent?' " said Keith Erickson, director of North and South American sales for Tanita. "It's a tool. It's not an absolute."

From that perspective, the monitors -- two from Omron, two from Tanita and one from Homedics -- came reasonably close to Ludlow's estimates. They ranged from a low of 18 percent (Tanita's higher-end Ironman Innerscan model, which also gave me credit for a heck of a lot of muscle, and a 25-year-old's metabolism), to a high of 20.9 percent (Tanita's less expensive model UM061). The two Omron models came up with similar numbers: 20.7 percent from the more-expensive Full Body Sensor (which, alas, also put me near the end of my life expectancy, based on estimates of muscle content and metabolism) and 20.1 percent from the company's hand-held HBF306 Body Logic, a model popular among personal trainers and health clubs because of its low cost and small size.

The Homedics 540 Health Station was the outlier, putting me at a whopping 29 percent fat. Switched to "athlete mode," a feature on many monitors that uses different assumptions about muscle tissue, it registered a lean 12 percent.

Anyone considering a purchase should keep an important point in mind: They are twitchy, especially when it comes to hydration levels.

In doing this test, I was careful to use all of the monitors just before I got into the dunk tank, so the condition of my body would be the same. Had I tested them an hour before, or an hour later, had a glass of water, eaten a meal or gone for a workout, the readings likely would have changed.

The manuals for the different retail monitors come with plenty of advice to address this: Don't measure after eating; don't measure after exercise; don't measure after drinking alcohol; don't measure in the morning because you're dehydrated; don't measure after showering because you've just been soaked with water.

The recommendation: Take any measurements around the same time of day, say just before supper, and don't pay too much attention to daily fluctuations.

"With any monitor, consistency of use is what's important," said Kristin Vitek, a product manager for Omron Healthcare.

Given all the caveats, I wonder how much value the machines really add. If you're attracted to technology and like to quantify things, this is a reasonable purchase, used correctly. But here's an alternative: Contract your abs and grab your belly. Anything in your hands doesn't need to be there.