With some time on my hands recently, I finally had the chance to try out a Full Body Sensor that a company called Omron sent me. The product is essentially a tricked-out bathroom scale: Not only does it tell you your weight and the percentage of your body fat, you get a health nut's dream of body statistics, including your BMI (body mass index) as well as the big kicker: your body's "physical" age. Turned out mine was 57. That would be totally fine except I'm 34. And I just ran a marathon. Wha…?

How could a product that promises a "comprehensive understanding of your body" (straight from the front of the box) get things so — presumably — wrong? The answer after the Continue jump.

After you stand on the scale and hold the wired handgrip in front of you, the body composition monitor (Model HBF-516) purports to read a lot of stuff in just a few seconds: your weight, body fat, BMI, visceral fat, skeletal muscle, resting metabolism, and physical age. Physical age is actually derived from the other measurements; it's calculated based on weight, body fat, and skeletal muscle. I was well within the "normal" parameters for weight and muscle, but not body fat. That one was, um, a little high. It seems my love of love juicy steaks and pancakes dripping with syrup may be catching up with me.

That still doesn't explain why this machine thinks my body's age is more than two decades away from my real one. I exercise regularly. I drink lots of water. I get a decent amount of sleep. Why should a little extra fat throw things off so much?

The answer is simple: the Full Body Sensor, which sells for about $120, wasn't designed for athletes. Omron made the product with the "general consumer" in mind, so a person in extremely good shape (with, say, unusually high muscle mass) could skew the numbers. The company says it's developing a device with an "athlete mode," which should come out in late 2009.

I like that explanation, because I don't like the other one: that my body really does have a physical age of 57, and that I desperately need to change my diet or I might suffer from a coronary in a few years. A scary thought, and one I would never have been thinking before stepping on this thing. Athletes should probably skip the Omron Full Body Sensor until the planned upgrade comes out… unless you're a fan of freaking yourself out.