Formula Medical Group
Apple Valley, CA

James Krider, MD

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Home Body-fat scales - how reliable?

CONCLUSION: Yes, you want an accurate home scale. First focus on the accuracy of the scale in measuring weight. Then, choose the bells-and-whistles you want to accompany an accurate scale. While the body-fat prediction may not be that accurate, you can monitor the change in body fat fairly reliably. Remember, even in the best of situations the scale will not reliably show a percent fat change for a weight loss less than about 5 pounds.

Bioimpedance measurements done in a medical office measure the current between the hand and foot under standardized conditions. This provides a measure of the resistance from both the upper and lower body and the lesser contribution of the torso. The readout is given as resistance and reactance, not body fat. The person administering the test then has the option of choosing the appropriate equation for your sex, age, ethnic background and level of obesity.

Home scales measure the electrical current from foot to foot. This means that the resistance is a reflection of the lower body only with no input from the torso or upper body. The equations are “locked” into the scale and cannot be changed. Some studies show that the foot to foot is OK in women with the pear shaped body, but totally lacking accuracy in men with the apple shaped body.

A foot scale only measures the lower body while a clinical BIA unit measures much more of the body.

Consumer Reports examined home body-fat scales in 1/2004. The two “winners” were the Taylor body fat analyzer and scale 5553 which they found the most accurate at measuring fat, but just OK as a weight scale. The best scale for weight was the Tanita BF-680, but the body-fat measurements weren’t very accurate.

Body-fat scales

Taylor Body Fat Analyzer and Scale 5553.

Tanita Scale Plus Body Fat Monitor BF-680.


1 Taylor

2 Tanita


Availability Most models at stores through December 2004 .






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Taylor Body Fat Analyzer and Scale 5553




Tanita Scale Plus Body Fat Monitor BF-680





Terraillon Body Fat Analyser TFA 20





Tanita Ultimate Scale 2001







Salter Body Fat Analyser Scale 968






Soehnle Body Balance Pacific 63656





The accuracy of any scale to measure weight is, I believe, the first and most important factor and the prediction of body fat is just simply fun. An interesting research article examined the accuracy of non-household scales. They examined 223 scales from primary care clinics, weight loss facilities, and fitness centers. Precision was validated using 100 lb., 150 lb., 200 lb., and 250 lb., certified weights. At the higher weights, more than 15% of these scales were off by more than 6 lbs.

So, if we have trouble obtaining accurate weight in a professional setting, how well are you doing at home? Chose the scale that gives you the best weight, then look for bells-and-whistles.

A literature search on Tanita, the most popular home body-fat scale, turned up 177 articles. Most studies were done with children, athletes, and otherwise lean persons. The results were all over the place, but showed the typical BIA pattern of overestimating fat in skinny persons and underestimating in heavier persons. Compared to some clinical BIA units the Tanita underestimated fat and had a wide limit of agreement.

This article was last reviewed February 10, 2006 by Dr. James Krider.

BIA test preparation
BIA home scales
Body circumference
Body circ technique
Body compartments
Body comp methods
Body measurements
Skinfold technique
Skinfold calipers

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