Exact Body Fat Percentage cannot be precisely determined, but multiple methods are available to estimate it. These include: a formula that uses your weight in pounds and waist circumference, the use of calipers to measure skin fold thickness, or bioelectrical impedance calculation. Some body fat is required for overall health. It plays an important role in protecting internal organs, providing energy, and regulating hormones. Excess body fat is linked to an increased risk for diseases such as cancer, diabetes, and heart disease.
Essential Body Fat
Minimum Required Fat
Men 6–13% F
Women + 32%
Methods of Calculating Body Fat
- Water Displacement Method
The Fat Cells in humans are composed almost entirely of pure Triglycerides with an average density of about 0.9 kilograms per liter. Most modern body composition laboratories today use the value of 1.1 kilograms per liter for the density of the “fat free mass”, a theoretical tissue composed of 72% water (density = 0.993), 21% protein (density = 1.340) and 7% mineral (density = 3.000) by weight. body density can be determined with great accuracy by completely submerging a person in water and calculating the volume of the displaced water from the weight of the displaced water. Estimation of body fat percentage from underwater weighinghas long been considered to be the best method available, especially in consideration of the cost and simplicity of the equipment.
- Air Displacement Method
A technique for measuring fat mass has been developed using the same principles as under water weighing. The technique uses air, as opposed to water and is known as Air Displacement Plethysmography (ADP). Subjects enter a sealed chamber that measures their body volume through the displacement of air in the chamber. Body volume is combined with body weight (mass) in order to determine body density. The technique then estimates the percentage of body fat and lean body mass (LBM) through known equations (for the density of fat and fat free mass).
- Bioelectrical Impedance Anaylsis
The bioelectrical impedance analysis (BIA) method is a more affordable but less accurate way to estimate body fat percentage. The general principle behind BIA: two conductors are attached to a person’s body and a small electric current is sent through the body. The resistance between the conductors will provide a measure of body fat, since the resistance to electricity varies between adipose, muscular and skeletal tissue. Fat-free mass (muscle) is a good conductor as it contains a large amount of water (approximately 73%) and electrolytes, while fat is anhydrous and a poor conductor of electric current.
- Skin Fold Method
The skinfold estimation methods are based on a skinfold test, also known as a pinch test, whereby a pinch of skin is precisely measured by calipers at several standardized points on the body to determine the subcutaneous fat layer thickness. These measurements are converted to an estimated body fat percentage by an equation. Some formulas require as few as three measurements, others as many as seven. The accuracy of these estimates is more dependent on a person’s unique body fat distribution than on the number of sites measured.
- BMI Method
Body fat can be estimated from one’s Body Mass Index (BMI). The BMI is calculated from an individual’s weight divided by the square of the height if expressed in kg/m2, multiplied by 703 if expressed in lbs/in2. Formulae for Fat
Calculate Your Body Fat
Child body fat % = (1.51 × BMI) − (0.70 × Age) − (3.6 × sex) + 1.4
Adult body fat % = (1.20 × BMI) + (0.23 × Age) − (10.8 × sex) − 5.4
Where sex place 1 for males and 0 for females.
- Why “Skinny” Isn’t Everything: Losing The Body Fat! (americanlivewire.com)