Comparing the Accuracy of Body Fat Scales

— -- Scales have evolved from simply stepping on a scale to see your weight at one moment in time to being able to track weight over time and connect with apps on a smartphone.

Scales also now measure body fat. “Good Morning America” invited three women to try six different consumer body fat scales.

The three women first had their body fat percentage measured by Dr. John Shepherd and his team at the University of California San Francisco’s Body Composition Lab. Shepherd considers these findings –- obtained using a body fat assessment device known as the Bod Pod -- the “gold standard” in the final comparisons.

The body fat scales tested by the women included those made by Tanita, Fitbit, Taylor, Withings, Weight Watchers and Qardio.

The scales ranged in price from $40 to $150. All six scales reported the weight correctly for all three women, with less than 1 percent of error from Dr. Shepherd’s findings.

On average, the Tanita scale, Taylor scale and Weight Watchers scale each reported our testers’ body fat 4 percent more than the “gold standard.”

The Withings scale reported our testers’ body fat 9 percent more than the “gold standard.” The Withings body analyzer uses a scientific technique that is widely recognized as the best method for at-home body mass measurement.

The Qardio scale reported our testers’ body fat 5 percent more than the “gold standard.”

We had a syncing error with the Fitbit scale – which 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 and some criticize the use of the Bod Pod as the “gold standard” and say their own testing confirms the accuracy of their products. They also tell us these products are meant to help users see trends over time.

Consumer Reports tested the same six scales in March and came to the conclusion that, “The results were unimpressive: None was very accurate.”

As of earlier this month, the Withings model is no longer on the market. The company has now released two new scales that test body fat among other things.

The scales still use the same technique to calculate body fat but, “the new electronics are more advanced and take even more exact readings,” Withings told ABC News.