“Take two measurements: your body-mass index and your waist measurement,” says Steven Heymsfield, M.D., a professor of metabolism and body composition at the Pennington Biomedical Research Center in Baton Rouge, La., and an expert on weight loss. Or you could just use a measuring tape and a calculator. If a smart scale isn't very good at determining your body fat, what’s a dieter to do? You could go to a lab with a Bod Pod for $75 per session. And the devices don’t work well if you have an artificial hip or knee because the man-made materials can interfere with the electric current. Results can also vary depending on whether your feet are wet or dry (they should be dry, according to the instructions), whether you recently exercised, and how much water you had to drink. Because the electric current passes through only your legs, the scales might underestimate body fat if you have a big belly but slimmer legs and overestimate it if you carry more weight on your hips and thighs. How a device errs may depend in part on body shape. At least they were consistent, though, so you can use the scales that scored better at body-fat repeatability to track relative gains and losses over time. The body-fat scale that came closest to the Bod Pod results was still off by up to 21 percent the worst performer was off by up to 34 percent. Based on that, the scales use built-in formulas to estimate the percentage of your weight that comes from fat.įor some of our test subjects, the scales overstated their body fat for others, the scales understated it. The resistance the current encounters as it travels depends on the proportion of fat and muscle tissue. That tiny current-much too low to feel or cause any harm-passes up one leg, through your pelvis, and down your other leg. The scales we tested measure body fat using an electric current that travels through your body when you step barefoot onto the device’s metal footpads.
Lumina fat iron before and after full#
(Research shows that method is as accurate as the other gold standard-measuring how much water a body displaces when dunked into a tank full of water-but the Bod Pod measure is quicker and easier to perform.) The egg-shaped device determines body fat by precisely recording the change in air pressure created when a body is sealed into a closed chamber. Six volunteers-three men and three women, some heavier, some slimmer-climbed into the Bod Pod. We know that because we got benchmark readings by using a measuring tool called a Bod Pod at Sacred Heart University in Fairfield, Conn. Rating a body-fat scale on its ability to gauge body fat was more complicated, and the results were unimpressive: None was very accurate. Customers can ask for a refund or replacement at (For more details on all six scales, check our Ratings and buying guide.) Consumer Reports investigated Qardio's fix here's what we found. When we asked Qardio to respond to our findings, the company told us that it was aware of the problem and said it was corrected. To do that, we had seven men and eight women step on an electronic lab scale, which we used as a control, then weighed them four times over two days on each of the scales.įive of the body-fat scales read weight accurately, but one, the Qardio QardioBase (which happened to be one of the priciest), routinely overestimated weight by 6 to 10 pounds.
We checked first to see how well they performed the most basic function: giving users an accurate weight.
We looked at six digital scales that gave readings for weight and body fat (some calculate BMI as well), ranging in price from $40 to $150.
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