Tuesday, January 8, 2008

Fat cracks (at my expense): Fit N Fresh Body Fat Analyzer

One of my 2008 New Year's resolutions was to lose 1% body fat. To make sure I actually meet that goal, I need to have some way of tracking my body fat percentage. That's where this Fit N Fresh body fat analyzer comes in. I bought this for roughly $5 at Vitacost.com. Except there, it was listed as MEDport Fit & Healthy. I think in my search for reviews of this unit, I found other very similar body fat analyzers with slightly different names and packaging. It's probably made by some OEM and rebranded.

The device has a clock and alarm feature. It's not the primary purpose for which I bought it, but I find the extra features moderately handy. That may be just because I never wear a watch, so I'm dependent on my computer or other devices around me to keep track of time. It uses an included CR2025 lithium button cell battery, which I imagine should last a decently long time. In usage, you switch from the clock mode to the measurement mode, hit start, and press your thumbs to the two shiny disc electrodes. In 8 seconds or less, you should have a reading. You do need to specify your weight, height, age, and sex for the measurement. Fortunately, those values are saved, and there are 8 memory slots. The whole family can join in the fun and see just how chunky they are.

This meter works by using bioimpedance, which is the most popular modality used by consumer body fat analyzers. Basically, an imperceptible low current is passed through your body from one electrode to another. Muscle and fat have different impedances, or resistance to the flow of the electric current. The measured impedance depends on your ratio of muscle to fat (as well as other tissues), and your body fat percentage can be inferred from the measured impedance value. Theoretically bioimpedance can measure your body fat percentage pretty accurately. However, the accuracy of conversion from measured impedance to fat percentage is highly dependent on the mathematical model used, body type, age, hydration level, what you've eaten recently, and maybe even the phase of the moon. Ok, scratch the phase of the moon cause, but you get the idea.

You might guess that something this cheap probably isn't that accurate. And you'd be right. This body fat analyzer suffers from all the downsides of consumer bioimpedance measurements. My body fat was measured at 11.5% just one month ago. I registered at 26.2% on this bad boy. Either I've become nearly obese over the holidays, or this piece of sh... errr, I mean device... will never measure my absolute body fat percentage accurately. My better half also tried it, and I can't mention the ridiculous value it registered without fearing for my well-being.

Most consumer grade bioimpedance based fat analyzers are going to be wildly inaccurate for significant subgroups of people, particularly for the highly athletic and really overweight folks. Really muscular and lean people will likely register way too high, and the really overweight will likely register far lower than reality. Is this body fat analyzer junk? Well, if you're looking for absolute accuracy, most certainly yes. I bought it for relative accuracy (i.e. precision for you science terminology sticklers). I think it might suffice for that purpose. I just need to know the change in my body fat percentage over time, not my absolute amount of body fat. In my brief tests so far, the readings have been consistent in their inaccuracy (varying by 0.1-0.2%). At least I know that it won't waffle in its brutal claims about my beer gut.

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