Lean Body Mass & Fat Percentage Question

rusialeelee
rusialeelee Posts: 143
in Health and Weight Loss
Two online body fat percentage calc. have said I'm either 25.5% or 26.5% body fat.

That leaves me at 126 lb or 128 lb, respectively, of lean body mass.

And I'm trying to get down to 135... is it ok to have only ~10lb of fat on me?

Are these calculations way off?

My Stats
Height: 5'7
Weight: 172.8lb
Age: 21
Wrist: 6.3" (s/m frame)

Replies

  • geekyjock76
    geekyjock76 Posts: 2,720 Member
    Let's do some math...

    128 lean body mass divided by .945 = estimated body weight of 135 lbs.

    You'd have to get down to 4.5% body fat to be 135 lbs which likely won't happen.

    But I would not put too much faith in online body composition calculators.
  • geekyjock76
    geekyjock76 Posts: 2,720 Member
    To estimate how much you'd weigh at a certain body fat goal, you need to do the following:

    1. Estimate at what body fat percentage would lead to the desired body weight.
    2. Take 100 and subtract hypothetical BF%.
    3. Turn into decimal form.
    4. Divide lean body mass with answer.

    I guessed 5.5% so...

    100 - 5.5 = 94.5; becomes .945

    128 divided by .945 = estimated desired weight of 135.
  • rusialeelee
    rusialeelee Posts: 143
    I plugged in 135 lb into a calculator and guesstimated my waist to be 27 inches= size 6?

    it said my BF% would be 21%......



    ugh... confused.

    BUMP!
  • rusialeelee
    rusialeelee Posts: 143
    why am I 126-127 LBM? that's a lot...
    aren't most girls usually around 110?
  • rusialeelee
    rusialeelee Posts: 143
    why am I 126-127 LBM? that's a lot...
    aren't most girls usually around 110?

    "Lean mass includes muscle, bones, organs, water. If you actually were 178 lbs of LBM now at 269 lbs, when you lose weight your LBM will also go down anyway along with your fat percentage (assuming you lose mainly fat), so you wouldn't be 180 lbs of muscle. "

    Read this somewhere in the forums.
    Hopefully my LBM decreases simulatenously.
  • geekyjock76
    geekyjock76 Posts: 2,720 Member
    I wouldn't worry about it. Instead, go get tested in person through other means whether it be hydrostatic weighing, calipers, bioimpedance, etc. 127 lean body mass does seem a bit high for someone at 5'7" with small joints.
  • michellekicks
    michellekicks Posts: 3,624 Member
    A sports nutrition/coach I saw estimated you need about 25 lbs of fat for the average woman to function properly.

    EDIT: This was the guy who did my DEXA scan to tell me I have 120 lbs of lean mass. I had about 133 lbs of lean mass in high school.
  • Awkward30
    Awkward30 Posts: 1,927 Member
    http://www.exrx.net/Calculators/WeightBodyComp.html can do the math for you.

    So, if you aren't using calipers, the absolute number that you are getting isn't likely accurate.

    You can use google and double check the reasonableness of estimates by pictures like
    bodyfat_examples.jpg

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