How do electronic body fat measuring devices work, and are they accurate?

ask our dietitian your question todaywhere technology meets health and fitness


I am curious on how the hand-held and scales work when measuring body fat.
There seems to be quite a difference, when measuring body, when I compare the percentage from one device to the next.
I know calipers and a water dunking are more accurate, however, what average should I consider with the tools I do have and use on a daily basis?
Regards, – Donna



The reason you are seeing so much difference in body fat percentage is that your hand-held device and scale estimate BF% based on the flow of energy from the contact point, through your body to the receiving point. (Fat impedes the flow whereas muscle helps it along.) This method is called bioelectrical-impedence analysis, or BIA for short. The equipment uses the path of least resistance. A hand-held analyzer’s flow is mostly through the upper body: hand up the arm, through upper torso, down other arm to hand. A scale analyzer’s flow is mostly lower body: foot up the leg, through lower torso, down other leg to foot. Depending on how fat is distributed throughout the body one can get varying results from the two types of BIA you describe.

Case in point: a pear-shaped person with lean arms, back and chest having more hip, thigh and buttock fat reads much lower BF% on a hand-held than on a scale analyzer. A person with an inverse triangle body shape might have his or her lower reading from the scale.

There are standing devices using foot and hand contacts which are more accurate as they assess segments of your body. These are stationary and quite expensive relative to the small portable BIA tools you’re accustomed to. A handful of our clubs have such equipment in place.


– Debbie J., MS, RD

Do you have a question about your diet or nutrition?

Ask our dietitian by submitting your question to or simply ask it in the COMMENTS section below. To learn how to follow the “Ask Our Dietitian” Q&A CLICK HERE!

Debbie James is a registered dietitian. Any views or opinions presented in this article are solely those of the author and do not necessarily represent the opinions or recommendations of Fitness International, LLC.

Posted on May 8, 2015, in Ask Our Dietitian, Health, Helpful, LA Fitness Blog - Living Healthy, Nutrition, Weight Loss and tagged , , , , , , , , , , , , , , , , , , , . Bookmark the permalink. 1 Comment.

  1. Charlotte Grieselhuber

    Could someone tell me what machines to use just for toning up — I used the treadmill but would like to do the following on machine — a couple of machines for arms – a coupld of machines for legs, a couple of machines for “butt” and a couple of machines/exercises for stomach — maybe a shoulder or two machine —- thanks so much. I am 69 years of age – female and just want to keep toned.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: