Anyone Know About Body Fat Percentages?

I have been worried about my weight going too low so I did some looking up online.  I weigh 106lbs right now and according to my scale I have about 23% body fat.  So I used the calculations I found online and according to them it says that I have about 24lbs of fat and about 82lbs of lean mass.  That just doesn't sound right.  I am thinking maybe I should go somewhere and have my body fat percentage tested officially so I can know what I am dealing with.  According to these calculations if I get to about 103lbs I would have about 20% body fat.  Right now I am at the "Fitness" level.  If I get to 20% I would be at the "Athlete" level.  I am by no means an athlete.  I do want to build up more muscle and I am hoping I am doing that with my exercise but the exercise I do is cardiovascular.  Do I need to do some strength training to build up muscle?
To me these numbers just show how out of shape I am, without much muscle.  Does anyone know what it means or how accurate the scales are in showing body fat?

I don't know much about it, but when I was in a weight loss program with my OB/GYN, they had this scale that would print out a paper that showed all kind of information and one of them was body fat.  I don't know if it was the percentage or if it actually measured it.  You had to weigh barefoot and not have any hose or socks or any kind on - so I'm not sure.
At the hospital one time they had a hand held thing that measured body fat - again not sure how it worked.
I have read of people being dipped in water and weighed and all kinds of things to get their body fat percentages - I'm interested in this also - maybe someone will post some info.
Linda

The scales really aren't very accurate.  You would either need to do a water displacement test (hydrostatic weighing?) or a Bodpod.

To build muscle, you do need to do strength training. Aerobic exercise isn't enough.

"Do I need to do some strength training to build up muscle?" Yes. Cardio burns fat primarily.

For body fat percentages, the scales and the handheld gizmo use bio-impedance. This means they shoot mild electricity through you and measure how much comes out the other end. Scales where they shoot it through your foot tend to give more weight to the bottom half of your body while the handheld ones give more credit to your upper body.

This method varies quite a bit based on your hydration level as well. It also has a large estimation component. For example, my scale lets me tell it whether or not I'm an athlete. Based on that, it gives a different body fat % number. Obviously, my body fat % is what it is so one (or both) of those numbers is wrong.

The most accurate measure is a DEXA scan - they can set up the machine so it scans more than your bones and it's very accurate because the machine can tell the difference between fat, bones, water, muscle and organs.

Calipers can be very accurate or they can be very inaccurate. It depends on the skill of the people using them. They tend not to estimate your viseral fat though. So a lot of times they measure low. OTOH, they tend to be thrown off by loose skin so for us they can be too high.

Bodpod and Dunk tank (aka hydrostatic) measure body fat based on displacment. (Bodpod displaces air and dunk tank displaces water.) They are both very accurate. Maybe not as accurate as DEXA but they tend to be way cheaper and the difference in accuracy probably isn't worth the difference in price to most people.

Thank you for all the good information.

Just saw your post--I was tested in a Bodpod on 7/22/11 and I also have a Tanita scale that is supposed to measure body fat percentage.  The Bodpod gave a reading of 42% fat and my scale said 40%, so not hugely different.

I am lifting weights now to build muscle, going back for another Bodpod evaluation in 5 months and hoping to be in the "Fit" range at around 30%.