Monday, January 18, 2010

Body Fat Percentage and Lean Body Mass (LBM)

To find your Lean Body Mass, you must first find your Body Fat percentage.

This requires you to get a friend to help you pinch 7 different locations on your body and take Skin Fold Measurements. You can use a caliper, or you can pinch, hold your fingers in place, then measure the space between your fingers. Obviously calipers are more accurate, but as I do not have any, we used the finger pinch method. Because of the increased chance of error due to the finger pinch method, I know to take the % Body Fat and therefore the Lean Body Mass totals with a grain of salt. To get more accurate values, I will have to buy a caliper and take monthly measurements, then compare the LBM results over the extent of this year long experiment.

Skinfold Measurements
Here are the different locations on the body that require measurement, as stated at http://www.gain-weight-muscle-fast.com/skinfold-measurements.html, which also has helpful pictures.



  • Chest - For men, get a diagonal pinch half way between the armpit and the nipple. Women need a diagonal pinch 1/3 of the way from the arm pit to the nipple.
  • Midaxillary - A vertical pinch on the midaxillary line which runs directly down from the center of the armpit. Raise your arm above your head and have your partner get these skinfold measurements just below the level of your nipple.
  • Subprailiac - A diagonal pinch just above the front forward protrusion of the hip bone.
  • Abdominal - A vertical pinch about one inch from your belly button.
  • Thigh - A vertical pinch halfway between the knee and top of the thigh.
  • Tricep - A vertical pinch halfway between the shoulder and the elbow.
  • Subscapular - A diagonal pinch directly below the shoulder blade.
Here are my measurements:
  • Chest - 1.5 " = 38.1 mm
  • Midaxillary - 2" = 50.8 mm
  • Subprailiac - 2" = 50.8 mm
  • Abdominal - 2.75" = 69.85 mm
  • Thigh - 0" (really, I couldn't pinch anything on the top of the thigh, but if we were measuring inner thigh, well that's another story)
  • Tricep - 1.5" = 38.1 mm
  • Subscapular - 2" = 50.8 mm
Now, I could go through and do the calculation based on the below formula, but I'm going to just us the calculator at http://www.gain-weight-muscle-fast.com/body-fat-calculator.html

Here are my results for January 2010:

Bone Density = 1.002
% Body Fat = 44.10 %
Body Fat in lbs = 105.40 lbs of fat and water
Lean Body Mass (LBM) = 133.60 lbs of LBM

What this tells me is that my goal of 140 lbs is possible, but I'd have to get below 10% body fat. Only future caliper measurements will tell me if this LBM is correct and if I need to adjust my goal.

The calculations that came to the above totals (listed below) are based on Jackson-Pollocks' formulas for bone density, then based on that value finding the body fat percentage using Siri's formula.

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Here are the % Body Fat formulas for Men and Women:


Body Fat Percentage Man

Seven Skinfold Sites 
(all 7 sites from above, SUM7 is the sum of all the measurements in mm)

Bone Density = 
1.112 - (0.00043499 * SUM7) + (0.00000055 * SUM7²) - 
(0.00028826 * Age)
Body Fat Percentage =
[(4.95/Bone Density) - 4.5] 100
 

Three Skinfold Sites 
(Chest, Abdominal, and Thigh sites from above, SUM3 is the sum of these sites in mm)

Bone Density =
1.1093800 - (0.0008267 * SUM3) + (0.0000016 * SUM3²) -
(0.0002574 * Age)
Body Fat Percentage =
[(4.95/Bone Density) - 4.5] 100
 

Body Fat Percentage Woman

Seven Skinfold Sites 
(all 7 sites from above, SUM7 is the sum of all the measurements in mm)

Bone Density =
1.097 - (0.00046971 * SUM7) + 
(0.00000056 * SUM7²) - (0.00012828 * AGE)
Body Fat Percentage =
[(4.95/Bone Density) - 4.5] 100
 

Three Skinfold Sites 
(Tricep, Suprailiac, and Thigh sites from above, SUM3 is the some of these three sites in mm)

Bone Density =
1.0994921 - (0.0009929 * SUM3) +
(0.0000023 * SUM3²) - 
(0.0001392 * AGE)
Body Fat Percentage =
[(4.95/Bone Density) - 4.5] 100

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