How Accurate Are At-Home Body Fat Scales? ABC Investigates

ABC uses the BOD POD to investigate the accuracy of body fat scales

Many people rely on scales for measuring weight and body fat. However, the accuracy of these scales is questionable, according to a recent investigation by ABC.

Three women had their body fat measured by ABC's experts, Dr. John shepherd and his team at the university of California San Francisco (UCSF) body composition lab. ABC compared the BOD POD results from the lab with the data from the latest models of scales such as Fitbit, Withings, Tanita and Qardio. The results were surprising, to say the least.

(P.S. Don't miss the fun part at the end of the video!).




Transcript for Comparing the Accuracy of Body Fat Scales

Now "Gma investigates" Friday morning the scales measuring weight and body fat that so many rely on but now the accuracy of those Numbers is being questioned. Our Becky Worley takes a look at the high-tech scales. Reporter: Scales have really evolved from connecting with apps to measuring body fat. But how accurately? We invited three brave women to try out six consumer body fat scales ranking from price from 40 to $150. This is our gold standard for percent body fat. Reporter: We start in this while contraption called the BOD POD by measuring body fat percentages for all three women. Our experts, Dr. John shepherd and his team at the university of California San Francisco body composition lab. We're trying out the latest models of scales from tunita, fitbit, Taylor, withings, weight watchesary qardio. All six reported weight correctly for all three women with less than 1% of error from our gold standard but the body fat percentages, that's a different story. For Sara her body fat percentage nearly 34%. Out of the six scales, 38.6. Reporter: Withings was off the most reported almost 39%. I don't know if I want to buy one at all. Reporter: For lose ser her percentage, 27% but for her the withings scale reported 37%. That's more than 10% off. Throw it out the window. Reporter: And for Natalie, nearly 16%. Whoa. Reporter: The withings scale has more than 14% off at 30%. I think getting a professional Reading will be more accurate. Reporter: How did the scales size up. Between our testers and when I gave them a go. Tanita represented it 4% more than our gold standard. Taylor on average, also more than 4%. Weight watchers, 4%, qardio, 5% and withings, 9%. We did have a sinking error with the fitbit says may have been due to a wi-fi problem so we are not reporting those results. We reached out to all the companies in our story, some criticized the use of the BOD POD as our gold standard and say their own testing confirms the accuracy of their products and add these are meant to help users see trends over time. Withings told us while it cannot comment on our findings it uses a specific technique widely recognized as the best method. The model is no longer on the market and the company out with two new scales that test body fat among other things, they still use the same technique to calculate body fat but tells us the new electronics are more advanced and take even more exact Readings. In March "Consumer reports" tested the same six and came to sim what are conclusions writing "The results were unimpressive none was very accurate". Technology is advancing and I think it will get better. Reporter: For our testers -- Maybe it's helpful to kind of keep trends and track how they're moving up or down. Reporter: I've used one of these body fat scales ever since I was trying to lose the baby weight after I had my twins. Many times the body fat analysis on my scale telling me I was outside of healthy norms. But I got my body fat tested at ucsf too and found out my scale has been overestimating my body fat by an extra 17 pounds. I'm channeling Oprah here with this lard but my scales told me I had this much more fat than I really do and, David, when it comes to body image perception matters. So at least now I know to factor in this much in my case margin of error. That's not even close. That's just incredible when you show it visually. Becky, we've always thought you looked amazing so who needs the scale in your case? Have a great weekend. It's really eye-opening stuff. Thanks, beck. Ginger zee tracking so much.

This transcript has been automatically generated and may not be 100% accurate.