How Do Body Fat Scales Work?

Introduction

When it comes to obesity, body fat is often the culprit behind the increased risks that come with being obese, including heart disease, diabetes and even some forms of cancer. Body fat can be measured in a variety of ways, some more accurate than others. For example, calculating your body mass index (BMI) can give a very rough estimate of how much fat your body contains. On the other hand, using underwater weighing can give a pretty accurate result for body fat. Somewhere in the middle in terms of accuracy is the use of a body fat scale.

Process

Body fat scales look very similar to a regular household weighing scale. One difference is the presence of two metal plates on the top. Before stepping on the scale, you input your height. The body fat scale will automatically calculate your weight. In some scales, there is also an option to put in a clothing allowance to offset whatever clothes you may be wearing. Once all the information has been inputed, you step on the scale and wait for the scale to notify you that you can get off. At this point, the scale will display an estimated body fat percentage.

Bioelectrical Impedance Analysis (BIA)

Body fat scales work using a process called bioelectrical impedance analysis (BIA). When you step on the metal plates of a body fat scale, a safe electrical current is sent through your feet into your body. The current travels through your body tissues until it returns to the scale. Because electrical current runs better through water and other tissues of the body than fat, the scale can measure how much impedance occurred during the transfer of electricity. From that impedance measurement, the scale uses a host of complex mathematical equations to determine an estimate of your body fat.

Accuracy

Although a body fat scale can give you a better estimate of body fat than many other methods, it is not completely accurate. There are many things that can throw off a body fat measurement. First, dehydration can affect your readings. Dehydration can occur from not drinking enough water, or from intense exercise directly before getting on the scale. Excessive alcohol consumption can also throw off your scale's measurements. The type of scale you use can also affect your readings. Some scales only take height and weight, while others are much more detailed, asking for things such as your gender or fitness level. These added pieces of information can help the body fat scale give a more accurate result.