Bioelectrical Impedance Analysis (BIA)
What is body fat percentage?
Body fat percentage is the proportion of fat in an individual's body. Excess body fat has previously been determined by measuring weight against height, but body fat is not always visible and cannot be measured on an ordinary scale. Obesity, which indicates a high degree of excess body fat, has been linked to high blood pressure, heart disease, diabetes, cancer, and other disabling conditions.
Body fat percentage measurement
Calculation of Body Fat %
Lukaski & Bolonchuk's (1988) formula for total body water (TBW) is:
An athlete is a male, 25 years old, height 170cm, weight 65kg - measured resistance is 382
The hydration constant of the fat-free mass (FFM) is 0.73, so we can determine the FFM
The Fat Mass = Weight - FFM = 65 - 53.01 = 11.99kg
Body Fat % = Fat Mass ÷ Weight x 100 = 11.99 ÷ 65 x 100 = 18.5%
Body fat percentage fluctuations
Our eating habits, lifestyle and the amount of exercise we perform all affect our weight and hydration levels. Since BIA relies on the fluid levels of 'fat-free mass', such as muscle tissue, certain factors can alter an individual's body fat reading. For example:
In general, there is less fluctuation in a person's body weight and hydration levels between the late afternoon and the early evening (two hours after eating lunch and before the evening meal). The graph above shows my Body Fat % fluctuations throughout the day.
However, as everyone's daily routine and eating habits are different, you should determine the most suitable time to measure your body fat.
The use of body fat scales only measures the lower part of the body's resistance and therefore may not provide an accurate reading of your body fat.
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