Body Fat Index

Body Fat Index Also Know As Body Fat Percentage

An person’s total body fat percentage is the total weight of the person’s fat divided by the person’s weight and reflects both essential fat and storage fat. Essential fat is that amount necessary for maintenance of life and reproductive functions. The percentage for women is greater than that for men, due to the demands of childbearing and other hormonal functions. Essential fat is 2–5% in men, and 10–13% in women. Storage fat consists of fat accumulation in adipose tissue, part of which protects internal organs in the chest and abdomen. The minimum recommended total body fat percentage exceeds the essential fat percentage value reported above. A number of online tools are available for calculating estimated body fat percentage.

Recommended Body Fat Index

Some body fat percentage levels are more culturally valued than others, and some are related to better health or improved athletic performance. Ideal percentages are also based on age categories as well.

According to Thomas A. Owens, M.D. (Departments of Internal Medicine and Pediatrics, Duke University Medical Center, Durham, NC), body fat percentage is categorized as follows:

Body Fat Index Measurement Technique

There also exist formulas for estimating body fat percentage from an individual’s weight and girth measurements. For example, the U.S. Navy Circumference method compares abdomen or waist and hips measurements to neck measurement and height and other sites claim to estimate one’s body fat percentage by a conversion from the body mass index. In the Navy the method is known as the “rope and choke.” It is not uncommon for Chiefs to take advantage of flaws in the procedure to pass those who are otherwise out of standards.

The U.S. Marine Corps and U.S. Army also rely on the Height and Circumference method. For males, they measure the neck and waist just above the navel. Females are measured around the hips, waist, and neck. These measurements are compared to a height/weight chart with age factored in as well. This method is used because it is a cheap and convenient way to implement a body fat test throughout the entire Department of Defense. This method poses a particular threat of inaccuracy because one can hold one’s stomach in more if needed to pass the requirements, and/or flare the neck out and make it bigger resulting in a lower body fat percentage.

Due to different body compositions, those with larger necks have an advantage over those with smaller necks.

Another well-known method using height and circumference is the YMCA formula. It uses only body weight in pounds, and waist in inches (at navel), to calculate body fat percentage using the formulas,

For Women       {-76.76 + (4.15 x waist) - 0.082 x weight} divided by your weight

For Men            {-98.42 + (4.15 x waist) - 0.082 x weight} divided by your weight

Here is an example for a man that weighs 205 lbs and has a waist of 36 inches

{-98.42 + (4.15 x 36) - (0.082 x 205)} divided by 205

{(149.4 - 98.42) - 16.81}/205

(50.98-16.81)/205

34.17/205

.166 = 16.6 %