Tuesday, January 24, 2012

PSA - Body Fat and BMI

Disclaimer: I am not a doctor, nutritionist, or fitness guru. I am sharing what I've learned through research and experience; you all must use your own judgment in deciding what is best for your and your own health, including checking with your doctor before beginning any exercise or dietary program.

BMI or Body Mass Index was developed by Belgium statistician Adolph Quelet in the 1800’s. His intent was this tool was to be used to measure the obesity of the general population, not the fatness of an individual. That being said, since many people and even physicians still use this measurement, here is the formula for calculating your BMI and what the results mean.

Basic BMI Formula

(weight in pounds x 703) / (height in inches) squared

Example, using my own (gasp!) stats

(159 X 703) /(63x63) = 111777 /3969 = 28.1

BMI Interpretation

  • Below 18.5 = Underweight

  • 18.5 - 24.9 = Normal

  • 25 - 29.9 = Overweight

  • 30 & above = Obese

The BMI is not an accurate accounting of your overall health if you are exceptionally tall, short or muscular. According to this basic BMI formula, I am Overweight. I resent that Overweight label. Really, I DO! I'm down to a size 8 dress pant. That isn't overweight in my book. So I dug a little deeper to see if there was another measurement that would take into account actual body fat and how it's distributed over the body. I found it - it's called Body Fat Percentage.

Body Fat Percentage

Body fat percentage is exactly that: the percentage of total body weight comprised of fat. The best way to determine this is with pinch measurements, an immersion tank and one of those spiffy scales that sends an electric current through your body and magically determines how much of you is actual fat. Most of us don't have access to such equipment, so here's a formula that will give you a quick and dirty answer, along with an interpretation of the results.

Body Fat Percentage Formula for Women

  • F1, etc = Factor 1, etc

  • TBW = Total Body Weight

  • LBM = Lean Body Mass

  • BFW = Body Fat Weight

The Formula:

  • F1: (TBW x 0.732) + 8.987

  • F2: Wrist measurement (at fullest point) / 3.140

  • F3: Waist measurement (at naval) x 0.157

  • F4: Hip measurement (at fullest point) x 0.249

  • F5: Forearm measurement (at fullest point) x 0.434

  • LBM = F1 + F2 –F3 – F4 + F5

  • BFW = TBW – LBM

  • Body Fat Percentage = (BFW x100) divided by TBW
Here's an example of the math using my own stats - measurements taken this morning.
  • F1: (159 x 0.732) + 8.987 = 125.36

  • F2: 6.00 / 3.140 = 1.91

  • F3: 30 x 0.157 = 4.71

  • F4: 39 x 0.249 = 9.71

  • F5: 10.0 x 0.434 = 4.34

  • LBM = 125.36 + 1.91 – 4.71 – 9.71 + 4.34 = 117.19

  • BFW = 159 – 117.19 = 41.81

  • Body Fat Percentage = (41.81 x 100) /159 = 26.29%

Body Fat Percentage Interpretation for Women

  • 10-12% = Essential fat necessary to stay alive

  • 14-20% = Professional and Amateur Athletes

  • 21-24% = Fitness Buffs

  • 25-31% = Acceptable

  • 32-41% = Overweight

  • 42% or Higher = Obese

BMI VS Body Fat Percentage
BMI is the most widely use indicator of weight status but it really isn't very useful because it doesn't take into account bone mass, muscle mass or actual fat as it lies on your body. Bones are denser than muscles and twice as dense as fat. Body builders and other hyped up exercise maniacs, like Buff Chad, have a high BMI without being the least bit obese. In fact, Buff Chad WORKS at keeping his BMI around 34 (crazy!) According to the calculations above, I am in the overweight category in the BMI chart, but I come out in the acceptable range in body fat percentage.

I continue to work on my overall health, with plenty of exercise and responsible food consumption. And no cookies. My ulitmate goal will put me in the normal BMI range and in the fitness buff body fat range. For now, though, I'm happier considering the Body Fat Percentage over the BMI: it's a more realistic snapshot of how I really look and feel.

Note: Both the BMI and the Body Fat Percentage are just a couple of quasi-accurate measurements to give you an idea of your overall heath and a starting point for your health goals. If you fall into the obese categories, it would be wise to consult your Doctor for some very specific guidelines for nutrition, exercise and possibly medications.

Do the Math. Keep the Faith.
EMail Anglea Pea


Jo said...

Very useful info. Both numbers are just another way to monitor our overall health, as you said. It's just good to know our bodies as well as we can. Sometimes I choose to look the other way, though. ;-)

Julie said...

Thanks Angela for the info.
Take care and have a blessed week!!

Bethany said...

That is very good info. I know that a couple of the Gyms in this area have the equipment to get the body fat percentage. I would be afraid to know what mine would be like. Yikes.