Originally Published: May 2008
Do you know your body fat percentage? We all need to carry a certain amount of fat in our bodies; too much or too little puts our health on the line. Since appearances can be deceiving, here are some objective ways to measure the ratio between fat and muscle in our bodies.
We all carry fat on our frames and it seems that most of us would like to shed a lot of it. Yet, we need a certain amount of fat for our bodies to function properly. Fat regulates body temperature, cushions and insulates organs, protects connective tissue and stores most of the energy that we use. Maintaining an optimum percentage of body fat is the key to good health and an attractive physique.Researchers agree that the essential amount of body fat for women is 10-12% of their total body weight.
For men, the range is 2-4%. In other words, a 120 pound woman needs to have at least 12 to 14 pounds of fat on her frame, with the other 106 to 108 pounds being lean body mass such as bone, muscle, organs, blood and other tissue. Likewise, a 160 pound man should carry at least 3 to 6 pounds of fat. Optimal athletic performance requires a higher percentage of body fat.
When the percentage of body fat increases beyond approximately one-third of total body weight for women and one-quarter of total body weight for men, individuals are considered obese and run serious health risks, especially heart disease, diabetes, high blood pressure, gallstones, osteoarthritis and some cancers.
The following chart illustrates generally accepted body fat percentage categories:
| Classified | Women (% fat) | Men (% fat) |
|---|---|---|
| Essential Fat | 10-12% | 2-4% |
| Athletes | 14-20% | 6-13% |
| Fitness | 21-24% | 14-17% |
| Acceptable | 25-31% | 18-25% |
| Obese | 32% plus | 25% plus |
How do we measure body fat percentage?
A number of methods have been devised to measure body fat percentage, giving us our “Body Mass Index” (BMI). These instruments range from a simple mathematical calculation that anyone can do on their own to the latest in body imaging technology conducted by health professionals. Aside from the laboratory methods of Dual Energy X-Ray and Magnetic Resonance Imaging, which are not available to the general public, there are a few inexpensive and easy ways to measure body fat percentage.
Body Mass Index Calculation
A simple search on the internet for “Body Mass Index” will result in hundreds of hits for web-sites that offer an on-line calculator of body mass index. Input your height and weight (and sometimes gender and age), and you will be given your body mass index. To calculate your BMI yourself, take your weight in pounds and divide it by your height in inches squared. Then multiply your answer by 703. Obesity experts classify a person who has a BMI of less than 18.5 as underweight; normal is 18.5-24.9; overweight is 25-29.9; obese is over 30; and extremely obese is over 40.
While this simple calculation is widely used by medical and health professionals for a quick reading, it has definite limitations. The formula makes no distinction between fat and muscle and therefore only gives an accurate measurement for people of average musculature. Because muscle is 18% denser than fat, people who strength train will be considerably heavier than those who don’t, yet they may have a much lower percentage of body fat. For example, the BMI scores of 15 gold medal athletes at the Athens 2004 Olympics ranged from 26 to 34, placing them in the obese category.
Waist Circumference Calculations
By measuring waist circumference and comparing it to that of the hips in women and the neck in men, the US Department of Defense calculates the body fat percentage of their personnel (see the following). These measurements are compared to a height/weight chart with age factored in. This method is more accurate than simple height and weight comparisons, but it also has its limitations because no two people carry fat on their abdomens in the same proportion.
Skin Fold Measurements
With the use of calipers, measure a pinch of skin at several standardized points on the body to determine the subcutaneous fat layer thickness. By use of a formula, convert these measurements to an estimated body fat percentage (for example). This method measures only fat just under the skin and does not take into account internal fat deposits, particularly in the abdominal cavity.
Bioelectrical Impedance Analysis
Bioelectrical impedance analysis (BIA) uses two conductors attached to a person’s body. A small electrical current is sent through the body and the resistance between the conductors is measured and converted into a body fat percentage. The instrument is based on the concept that resistance to electricity varies between muscle and fat. Muscles are good conductors as they contain large amounts of water and electrolytes, whereas fat does not. Recently, body fat scales and hand held analyzers based on bioelectrical impedance have appeared on the market for home use and they have proven to be more accurate than simple BMI calculations.
Near-Infrared Interactance
In this technology, a beam of infra-red light is transmitted by a fiber optic probe through the skin of the biceps. The light is reflected from the underlying muscle but absorbed by the fat, so the amount reflected gives an indication of muscle/fat ratio. This method is simple, fast, non-invasive, and the equipment is relatively inexpensive. However, results have been mixed in the case of very lean and very obese people. As well, some question the validity of a single-site measurement at the biceps.
As you can see, there are a variety of diagnostic tools to help determine whether your body fat percentage lies within a healthy range. Used in conjunction with other health indicators, knowing your BMI will help you tailor your diet, exercise and lifestyle habits to make the most of your life.
Shawn Vint is also a regular contributor to the Fitness Town Health & Wellness On-line E-zine. For more great articles like this one, please visit here and sign-up to receive our free newsletter once per month.
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