Knowing how much you weigh can be beneficial, but knowing your body fat percentage can be even more enlightening. The Body Mass Index (BMI) is a tool developed for large populations to determine levels of obesity, but only frame size and weight were factored into the equation. As a result, a bodybuilder with 7% body fat may show up on the BMI index as being obese. For this reason it is more beneficial to focus on your body fat percentage than your BMI.
I think knowing your body composition is important for anyone who is trying to maintain a healthy weight. Body Fat can be measured in a variety of ways. Some are more affordable than others, some are more convenient, and some offer greater accuracy. Here's a summary of your options.
Skin calipers-Calipers are used to measure the thickness of various fat locations on the body and then these measurements are plugged into an equation. It is relatively accurate but there is great possibility of human error if the technician taking the measurements is unskilled or inconsistent. Some people don't like to have their fat manually pulled out and measured with a gauge either.
Bioelectrical Impedance-These are common in gyms or on body fat scales. A small electrical charge is sent through the body and your body fat is estimated by how long it takes to pass through your body. The electrical impulse travels faster through muscle than it does through fat. These are usually not as accurate since the charge may just arc through the upper or lower body and as a result may not give you a complete picture of your overall fat. Hydration levels can also skew the results.
Hydrostatic Weighing-This is an older method that uses Archimedes principles of water displacement. You will probably only find these at a University since they are so large and expensive. You sit in a little dunking chair and blow all the air out of your lungs, then you are lowered into a small pool of water as you hold still as long as you can. The water displacement is measured to help determine your body fat. It is difficult and awkward to do but very accurate.
The Bod Pod-The Bod Pod looks like Mork's egg spaceship. It is a small chamber that uses the same displacement principles previously discussed, but instead of water it uses air. You just hold still once inside for about a minute while it calculates your body fat.It is very accurate and easy to use. The disadvantage is that you may not like it if you are claustrophobic.
Dexa Scanning (Dual Energy X-Ray Absortiometry)-This tool was originally developed to analyze bone density. It is basically a bed you lie on as an X-ray slowly scans your body. It is slow but very accurate. It is also extremely expensive. Not only does it tell you what your body fat % is but it's detailed analysis breaks down exactly where the fat is throughout the body such as torso, arms, legs, etc.
Remember fat is not necessarily bad, your body needs a certain amount to be healthy. Unfortunately most Americans have exceeded the healthy level and are at a greater health risk due for a variety of diseases to having excess fat.