Principles of Estimating Body Fat Percentage

The Tanita Body Fat Monitor/Scale BF-572 allows you to estimate your weight and body fat percentage at home as easily as you measure your weight. This model also includes Tanita’s Graph feature, so you can track your results over time.

What is Body Fat Percentage?

Body fat percentage is the percentage of fat in your body. Until now, your absolute weight has determined whether or not you were considered overweight or obese. In recent years,the defini- tion of obesity has been refined to mean the presence of excess body fat. Too much body fat has been linked to conditions such as high blood pressure, heart disease, diabetes, cancer, and other disabling conditions.

The chart below shows four ranges of body fat percentage.

Body Fat Ranges for Standard Adults1., 2.

Underfat

Healthy

Overfat

Obese

Female 20–39

Age 40–59

60–79

0%

10%

20%

30%

40%

Male 20–39

Age 40–59

60–79

Underfat

Healthy

Overfat

Obese

1.Based on NIH/WHO BMI Guidelines.

2.As reported by Gallagher, et al., at NY Obesity Research Center.

To determine the percentage of body fat that is appropriate for your body, consult your physician.

The BIA Method

The BF-572 uses the BIA (Bioelectrical Impedance Analysis) method. In this method, a safe low-level electrical signal is passed through the body. It is dif- ficult for the signal to flow through fat in the human body, but easy to flow through moisture in the muscle and other body tissues. The difficulty with which a signal flows through a substance is called impedance. So the amount of fat in the body can be accurately estimated by measuring the impedance. The signal used is very low-level, making it safe and imperceptible.

Body Fat Percentage Fluctuations in a Day

Hydration levels in the body may affect body fat readings. Readings are usually highest in the early waking hours, since the body tends to be dehydrated after a long night’s sleep. For the most accurate reading, a person should take a body fat percentage reading at a consistent time of day under consistent conditions.

Besides this basic cycle of fluctuations in the daily body fat readings, variations may be caused by hydration changes in the body due to eating, drinking, menstruation, illness, exercising, and bathing. Daily body fat readings are unique to each person, and depend upon one’s lifestyle, job and activities.

The graph below shows an example of daily body fat percentage fluctuations, based on the BIA method.

Body Fat %

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21

20

19

18

17

6 am

10 am

2 pm

6 pm

10 pm Time

Advantages of Tanita’s BIA Method

Previously, body fat percentage was determined by measuring the thickness of subcutaneous fat by pinching it with calipers, or by laying a person on a scanning bed and passing a current from hand to foot. However, these methods present problems—professional skills are required, the procedures take time and are often invasive, and measurement values vary. Currently, the gold standard methods of fat percentage measurement are DEXA (dual energy x-ray absorp- tiometry) and Hydrodensitometry (underwater weighing).

Tanita’s BIA method uses equations derived from large, multi-ethnic population studies to predict body composition. Readings taken with Tanita’s BF-572 correlate highly with both DEXA (Tanita’s reference model) and Hydrodensitometry.

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