Lean body mass - I am SO confused

kristinmarie1986
kristinmarie1986 Posts: 23
in Health and Weight Loss
So I hate BMI and wanted another way to be able to watch my progress besides just pounds and inches (also fun).

I went to a body fat calculator (this one: http://www.active.com/fitness/calculators/bodyfat# ) which says my body fat is at 32%. Obviously a work in progress :)

So my question comes from the lean body mass. According to my weight and BF%, my lean body mass is 157 and my understanding of that is that basically I should not want to go under that number because that's all bones/organs/muscle/things I need to live. But I'm female and 5'4" and I really didn't think I had that much muscle on me. Like I suppose I have a medium-large frame (my wrists are about 7 inches), but still!!

Can someone please explain to me how lean body mass/body fat percentage works because I just can't understand 157 being the absolute lowest I could go and I feel like I'm not understanding this right and I am just very confused. (also fyi I have been lower than 157 many times before and my body fat was not at 0 obviously so I just don't know how this all works!)

Thanks!!

Replies

  • kristinmarie1986
    kristinmarie1986 Posts: 23
    bump :)
  • neandermagnon
    neandermagnon Posts: 7,436 Member
    That calculator isn't necessarily very accurate. Google Leigh Peele - her blog has a free download on body fat percentage that explains it all really, well, including how to measure it - and also pictures of women at different body fat percentages, to get an idea of what look you're aiming for, so how much fat you need to lose to get that kind of look.

    Your lean body mass is what you'd weigh at 0% body fat.... 13% body fat is what you don't really want to go below (this is female body builder level of body fat, i.e. extreme definition, and they don't stay that low all year round, they go up to maybe 17% in the off season)

    I have a large frame, I'm 5'1" and about 101lb lean body mass (about 130lb total weight) - just to give an idea for comparison. If you think it's overestimated your lean body mass, then get it measured other ways and see what they say. If you're getting a big difference in numbers from different methods, one or all of them are wrong. If you're getting roughly the same each time, then they're probably reasonably accurate.
  • kristinmarie1986
    kristinmarie1986 Posts: 23
    Thank you so much!! I did get a couple different answers - another site said I was only 29%. I will look up Leigh Peele! Thanks!
  • bokodasu
    bokodasu Posts: 629 Member
    It is bones and muscles and organs and stuff, but "stuff" includes water and blood and other things that you need less of if there's less of you, so yes, you can go under that amount (which is probably good because a 5'4" woman with 157 lbs of just muscle/bones/organs would have the entire bodybuilding community beating down her door for her secret and nobody needs that kind of pressure). And those calculations get less accurate the further away from average you are, so if you're 230 lbs, that's probabably... not right. Sorry.

    If you can get someone who's good at it to measure you with calipers, or a BodPod measurement, or even one of those handheld electronig thingies, that would be more accurate (but still not perfect). Still, better to have a better idea of where you're starting so you can see how far you've really come.
  • lvtruu1
    lvtruu1 Posts: 211 Member
    Thank you so much!! I did get a couple different answers - another site said I was only 29%. I will look up Leigh Peele! Thanks!

    Some where in the formula you are using is an error or multiple errors. I highly doubt your have that much LBM. If you are accurate, you'd have zero body fat at 157.

    Put it this way at 180 pounds if you had 20% BF you'd have 36 pounds of fat or a LBM of 144 pounds.
  • kristinmarie1986
    kristinmarie1986 Posts: 23

    Some where in the formula you are using is an error or multiple errors. I highly doubt your have that much LBM. If you are accurate, you'd have zero body fat at 157.

    Put it this way at 180 pounds if you had 20% BF you'd have 36 pounds of fat or a LBM of 144 pounds.

    Yes those calculators were VERY wrong! Which is what I assumed. I didn't think there was any way my body fat was less than 50%, much less that low. The calculator from the US Navy seemed to be much more accurate.

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