Monday, November 23, 2009

Fat Pressure

Warning: I'm going to ramble about science. Feel free to skip.

I checked a book out from the library called "Run for Life: the Real Woman's Guide to Running." It's a pretty good explanation of the biology and mechanics of running in regards to women's bodies. Anyway, I was particularly fascinated with the anatomy stuff: different muscle types, the cardiovascular system, and how joints work. But this stopped me in my tracks: "If you are overweight you should lose weight BEFORE starting a running program." Turns out that the extra weight puts extreme pressure on your knee and ankle joints. I mean, I knew that, but the description and terms like "psi" made me stop and visualize a heavy weight being dropped onto a pylon again and again. Obviously a bigger weight will do more damage than a small one.

So I wanted to know just how much my bigger weight is. I've been reading that your total body weight is not as important of an indicator as your fitness level, which is measured by percentage of body fat. For example, a body builder might weight more than me, but she's got more muscle and blood than I have. She would be more fit than me, even though she weighs more. I looked up what would be considered a healthy amount of fat and then took some measurements to calculate my own.

Obese woman: >32%
Average healthy woman: 25-31%
Physically fit woman: 21-24%
Elite athlete woman: 14-20%

Jen: 55%!

Over half of my body is fat. What a slap in the face.


  1. Are you sure you calculated that correctly? I thought you needed a special instrument to do that, using the back of your arm.

  2. well, let's look on the bright side... half of your body may be a little overweight, but the other half is an elite athlete woman! :-D

  3. The measurement points with calipers are generally your waist and the back of your arm. I doubt you have the calipers to measure your body mass index like a "professional" would. Did you use one of those calculating systems that you can find online? While it is certainly not unheard of, especially in the United States, to have a body fat percentage over 50%, I don't know how accurate your measuring system is.

    As for the impact deterioration of joints, the body builder can support heavier impact on the joints because the majority of the weight is comprised of tissue (muscle) that helps carry the weight and reduce impact on the joints. When the weight is comprised of tissue that doesn't aid is absorbing the impact (muscle), then it is more damaging. I suggest a lower impact cardiovascular exercise. Think biking. Even just walking briskly up steep hills will work wonders and reduce impact while raising your heart rate and building slow twitch muscle fiber.

  4. I did my homework first. I read up on multiple sites how to do it. There are several methods but two seem to be the most trusted and accurate. The first is the caliper method. The second is called the Navy method and it uses ratios of hips, waist, etc. I think the result is completely logical. I weigh 240 and I'm only 5'3". I need to lose half of that!