how to calculate body fat
>> Thursday, November 13, 2008
There are three main ways to calculate body fat:
- Home Body Fat Scales
- Skinfold Calipers (Callipers)
- Hydrostatic Weighing
Each of these body fat calculation methods has advantages and disadvantages.
Using Home Body Fat Scales to Measure Body Fat
Body fat scales claim to measure body fat quickly and conveniently. These body fat scales use the Bioelectrical Impedance method to measure your body fat percentage. A low-level electrical current is passed through your body and the "impedance", or opposition to the flow of current, is measured. The result is used in conjunction with your weight and other factors to determine your body fat percentage. Unfortunately, your body's "impedance level" can be altered by many factors besides body fat. For instance, the amount of water in your body, your skin temperature and recent physical activity can all adversely affect the results.So only by following strict rules can you hope to get an accurate measurement of your body fat using these scales. The most important rules to observe in order to make a more accurate calculation of your body fat are:
- Don't eat or drink for 4 hours before the body fat measurement test.
- Don't exercise for 12 hours before the test.
Notes:
- Some studies have shown variances as high as 8 percent when using the bioelectrical impedance method even if the rules are precisely followed.
- As with skinfold calipers (see below) there are different equations used to calculate body fat from your body density. These are usually pre-programmed into the machine.
- The best body fat scales tend to made by Tanita.
Using Skinfold Calipers (Callipers) to Measure Body Fat Skinfold Measurements
Measuring body fat with a set of body fat calipers is the most cost effective way to determine fat levels. But it's important to use them correctly. For instance, either have a professional take the measurements for you or buy a set of Accumeasure calipers (callipers) and follow the measuring instructions. Accumeasure are the only calipers than allow you to test yourself and most studies have shown that they are very accurate.
Using Hydrostatic Weighing to Measure Body Fat
Hydrostatic weighing (underwater weighing) is the most accurate way to calculate body fat - that is, if you can find a hydrostatic weighing tank.
How does hydrostatic weighing calculate body fat? By using Archimedes Principle. Your examiner first calculates your body density by measuring the amount of water you displace when you immerse yourself in water. Then a formula is used to calculate body fat based on your body density. The problem is finding a facility (University, major gym or fitness center) which has a hydrostatic weighing tank!!
Table 1. Body Fat Guidelines from American Council on Exercise
| Classification | Women (% Fat) | Men (% Fat) |
| Essential Fat | 10-12 percent | 2-4 percent |
| Athletes | 14-20 percent | 6-13 percent |
| Fitness | 21-24 percent | 14-17 percent |
| Acceptable | 25-31 percent | 18-25 percent |
Why Body Fat Measurement is Important
Body fat is an important element in successful weight control. Body fat requires fewer calories than muscle. So the less fat/more muscle we have, the more calories we can eat before gaining weight. Body fat is often expressed as our "Body Fat Percentage" or "Body Fat Percent." Body fat percentage is the amount of body-fat-tissue as a percentage of total body weight. If your total body weight is 160 pounds and you have 32 pounds of fat, your body fat percentage is 20 percent.
Body Fat Calculation and Health
The higher your percentage of fat above average levels, the higher your health risk for weight-related illness, like heart disease, high blood pressure, gallstones, type 2 diabetes, osteoarthritis, and certain cancers. Also, the higher your percentage of fat (and the smaller your percentage of muscle) the less calories you need to maintain your weight and therefore the easier it is to gain weight. This is because muscle is more metabolically active than fat tissue.
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