Friday, January 19, 2007

Body Fat

Inspired, perhaps, by my brother's decrying of the inaccuracy of web-based body fat measurements, a kind member of the blogging community (who may not want you to know he lives in my real world vicinity and therefore shall remain anonymous) has lent me his body fat scale. According to the scale, I have 20% body fat with my clothes on and 22% with my clothes off (this actually makes sense if you think about how it works). So, as it turns out, I need to shave off 7%, not 5.


Saule Cogneur said...

I've used similar scales before. I don't think they can get much closer than 25% of the actual value. The one I used required me to input my body type (regular or athletic) and height. At least you can use the scale to measure a relative body fat drop.

svoid said...

I really dislike the electronic scales and prefer the calipers. I have both right now. The measurement on the electronic scale can vary widely even under the exact same conditions a short period of time later. However, I feel like the measurement on my caliper is fairly consistent.

Melyngoch said...

Yeah. Seven percent and your clothes.

Anonymous said...

some info on the different techniques:

Bfat 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.

Some studies have shown variances as high as 8 percent when using the bioelectrical impedance method even if the rules are precisely followed.

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