Tuesday, March 1, 2011

Body Fat Equations

Last week, I decided to find out what the difference is between losing body fat and losing weight. I've heard about this often and after my last weigh-in of gaining 0.4 lbs, but losing 0.2% body fat, I was intrigued to say the least.

I found this website- Heath Check Systems, which presents a lot of very interesting information including equations to find out what your lean muscle mass and pounds of body fat you have. The most interesting part was where they talk about your weight loss goals being realistic and giving you the equations to figure it out as well as a handy dandy chart.

Let's take a look at the numbers of my last weigh-in...

Weight: 207.8
Body Fat: 40.8%

Initial body fat: 207.8 lbs x 0.408 fat = 84.78 lbs of fat (yikes!)

Lean body mass: 207.8 total - 84.78 fat = 123.02 lbs (bones, organs, muscle and all else)

I was thinking that I needed to lose 100 lbs to be a normal weight for my height- that would make me about 118 lbs. As you can see, all the important stuff in my body weighs 123 lbs and by the chart, a woman shouldn't go below 10% of essential body fat. The lowest I can weigh is...

123.02 lean body mass x 1.10 = 135.32 lbs lowest possible weight I can be

However, 10% body fat is like an Olympic Athlete body. I don't need that. I would be happy with 20-25%. 

123.02 x 1.2 or x 1.25 = 147.62 lbs - 153.78 lbs (Goal Weight)

My temporary goal weight was around 150 lbs, it seems like I was right on with my estimate. But before I started to lose a couple years ago, I thought I needed to lose 100 lbs. Knowing that I need to lose about half that is very encouraging and my temporary goal is now my ultimate goal!

I did a few different calculations than the webpage to make it easier and more clear. I'm not sure if the equations given are totally accurate or not, but it seems to make sense.

If anyone knows anything about calculating ideal weight or body fat % I would love to hear it!


  1. Girl, I don't know jack about it (beside the fact I know have have LOTS of it!) other than I weigh right at what you do and I was thinking I needed to weigh about 150 lb too. I would have a normal BMI at that point and that is what I am aiming for. Eat anything new or good lately? I am starting to get in a rut, eating the same things over and over.

  2. As i don't weigh, I similarly don't know other figures like body fat. I am very interested in your approach though, its very scientific and seems very firmly rooted in the facts, which has to be a good thingI will revisit this, because I will weigh when I am ready.
    I absolutely love the new blog colour - its beautiful