I have looked at variouis websites, and have gotten confused between Body Fat Index and Body Mass Index.

They say that for accurate BFI you need calipers, and BMI is calculated (American) Weight x 704.5 divided by height squared. Yet, in most charts I see, the resulting numbers come out to the same thing.

Can anyone explain the difference to me?

Thanks.

AJ

I don't think there's such thing as an official "Body fat index," per se. I think it's a term to describe different protocols for estimating body fat based on caliper measurements.

I know that BMI is a *very* general index of body weight with respect to height - it doesn't take body fat into account.

I think it's a coincidence that the BMI numbers are similar to body fat percent values. A healthy BMI is something like 19-25 for both men and women, but healthy body fat ranges are different. It's similar for women (19-25%), but for men, it's less. I think it's 10-15% or something like that (don't quote me.)

Interesting - I never noticed the similarity before.

Body Mass index is simply a number that mean how many pounds per square inch of you there are. It doesn't take into account square inches of WHAT. BMI is nothing more than a weight to height ratio. Two 6 foot tall men who both weight 230 will have the same BMI even though one is 'fat' and one is a super-lean body builder. This is why BMI is not a very helpful number.

Body fat PERCENT is a calculation based either on height, weight and measurements such as your waist and hips, or on caliper readings that show how much fat is beneath your skin. If we take the two guys above with the same BMI, we might find that one is 40% fat, meaning he has 120 lbs of bone, muscle and organs and 80 lbs of fat on him. The other might be 10% fat, meaning 180 lbs of the good stuff and only 20 lbs of fat. Same BMI, but big difference in percentage and body compostion.

Body fat percentage is a far more useful number than BMI. There are several websites that will let you calculate bodyfat percent based on tape measure numbers. I use this one:

http://www.linear-software.com/online.html

Make sure you pick the right calculator for your gender.

Have fun!

Friday

Just to further confuse...

The body fat *number* is useful, but nearly impossible to measure accurately. So it's the *change* that most people are more interested in, if they're trying to lose weight and/or get in shape.